VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: RedRotors on October 28, 2005, 01:37:55 pm
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Hi folks,
Since a few days, i read a lot of document about diesel engines, combustion process and mosly on pre-chamber engine. I will post some quote of the documents i read. As stated, IDI has a better potential for combustion and fuel mixture process. The industry jumped on the DI engine because they didn't want to invested to solve the major problem on IDI engine, the heat loss of the pre-chamber. By beeing able to insulate the chamber, to keep the heat loss minimal, great gains can be acheived, better performance, less noise and better mileage.
IDI engines are fueled by self-cleaning, single-hole, pintle-type nozzles. The combustion process is too complex to be explained here, but my above-mentioned SAE technical paper No. 960058 describes it in more detail. In general, it is a two-step combustion process characterized by its speed and tolerance of fuel-system inconsistencies that allows operation of present automotive engines (such as the Mercedes IDI engine mentioned above) up to 5000 rpm. Combustion is faster and more complete than with DI systems, with more of the fuel being consumed even with lower amounts of air per cycle (lower A/F ratio) at the same smoke level. Since no swirl is required in the main chamber, high-efficiency directed intake ports can be used instead of the helical ports employed by DI engines, and more air is processed to provide higher volumetric efficiency with smoke-limited A/F ratios of less than 20:1. The combination of higher volumetric efficiency, reduced port-pumping losses, higher engine speed and higher combustion efficiency at lower A/F ratios produce higher power; typically, 10-15% more power at the shaft for similar-displacement engines. The indicated cylinder power is even higher, but two factors contribute to high thermal losses, which are detrimental to power output and fuel consumption. The first is the pumping losses in and out of the pre-combustion chamber and the second is the heat losses through the pre-combustion chamber walls. The technical world has concluded that these problems are unsolvable for small engines, and interest in pre-combustion chamber combustion has been lost, in spite of the fact that the overwhelming majority of pre-combustion chamber combustion characteristics are, for small passenger cars, far superior to those of the DI system. The Ricardo side pre-combustion chamber has remained unchallenged, except by some modifications that other researchers have performed including some work that I have done, as described in my U.S. Pat. No. 5,417,189, issued May 23, 1995 and my aforementioned SAE technical paper No. 960058. The only new application of a pre-combustion chamber system combined with four valves can be found in the new Mercedes-Benz DOHC family. Even so, the pre-combustion chamber and injector tip in this DOHC family differ very little from the 1927 Mercedes-Benz designs. Therefore, to continue enjoying all the benefits of pre-combustion chamber engines, while improving the fuel consumption profile, it is important, amongst other measures, to minimize the two main sources of losses; that is, pumping and thermal as exhibited by the current Ricardo and Mercedes designs. In reality, it is not required that they be eliminated completely. The reason being, as already explained, that the energy released by combustion is far higher than that of the DI system due to the more efficient burn. Therefore, the IDI system can tolerate some losses and still be competitive with DI; however, both sources of heavy losses must be reduced.
Other four-cycle, four-valve American engines from Cooper Energy Services, as well as from Caterpillar and Waukesha have also used pre-combustion chambers for many years, some as pure IDI diesels; others as spark-ignited gas engines. The latter are very popular in environments where low emissions are already closely regulated. With the trend towards the use of pre-combustion chambers, it has been predicted that newer, more efficient pre-combustion chamber designs will be required to minimize the pre-combustion chamber heat losses through heat transfer.
The need to keep the pre-combustion chamber as hot as possible has been acknowledged from the earliest use of the Ricardo "Comet" pre-combustion chamber in 1929. In the "Comet" pre-combustion chamber, the lower inserted portion of the pre-combustion chamber, called the "cup", is made of exotic heat-resistant material such as Nimonic and is designed to maintain an insulating air gap between its sidewalls and the cavity bored inside the head so as to reduce the heat losses. However, with the "Comet" pre-combustion chamber, the upper cavity is typically machined in the structure of the cylinder head and is prone to crack because of the high thermal gradient between the hot inside of the pre-combustion chamber walls and the cooler outside walls exposed to the cooling media compounded by the rates of firing pressure and maximum firing pressures as the fuel is ignited. To avoid this problem the design uses a water jet, typically drilled across the head, between the two valve ports (these engines typically being two-valve engines), both to cool the bridge between the valves and to impinge on the pre-combustion chamber's upper cavity. The upper-half of the pre-combustion chamber, therefore, not only suffers from the normal heat losses through its walls made of parent material exposed to the cooling jacket, but also has to cope with water being impinged upon it to avoid cracking the wall. In the process, it loses a very considerable amount of heat energy.
Some engines, made by Isuzu and others in Japan over fifteen years ago, upgraded the material of the pre-combustion chamber "cup" from Nimonic to ceramics, which has a far lower heat transfer coefficient; however, the top half of the pre-combustion chamber was not changed and still suffered high heat losses. Developments under my direction, using the lower pre-combustion chamber cup from Isuzu engines on an experimental Chrysler engine, proved that the engine not only reduced its fuel consumption by 4-5%, started faster, and produced less noise, but that it also burned faster and cleaner, allowing the injection timing to be retarded for reduced NO.sub.x, as well as hydrocarbons, particulates and smoke. Recognizing the fact that the main losses were still through the upper-half of the pre-combustion chamber ; a heat shield designed for disposition inside the upper pre-combustion chamber cavity. The heat shield is intended to minimize the high heat losses of the pre-combustion chamber at this location by increasing the total wall thickness and creating an insulating air gap between the shield and the parent-metal cavity. It has been calculated that such shield could improve the engine's fuel consumption another 7-8 percent and all the other combustion parameters as well, by reducing the heat losses.
According to the engineers, IDI engine have more potentiel than DI engine and i believe in this theory. It's a long process, time consuming, but i will invest some of my free time to try to improve and overcome the problem with heat loss in the pre-chamber. I already a couple of ideas in mind and im calling all diesel head to share idea.
IDI can kick DI ass badly :twisted:
Any suggestion, comments are welcome.
Marc/
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Great read, Marc. Inspecting an IDI VW diesel head, I'm sort of amazed how crudely the upper prechamber is machined. Usually there are concentric circles from the machining process. Besides causing drag that seems like it would slow down the amount of swirl in the chamber, it also might soak up and rob away more heat energy than a highly-polished surface would.
Something that one of us could easily try is to apply a ceramic coating to the top of the pre-chamber and polish the surface. Ceramic coatings are now available for combustion chamber use / piston tops, etc that have a thermal transfer coefficient much much less than aluminum. I did a calculation once (for zirconium oxide coating, IIRC) and found that just a few thousandths thickness of that ceramic coating would give an equivalent thermal barrier as a thick slab of aluminum! Of course, measuring this kind of effect resulting from that very precisely may be more work than most of us would be up do doing. You see a lot of talk at the enthusiast level about comparing miles per gallon (which is a very crude and inaccurate way of measuring engine efficiency), but very little about brake specific fuel consumption. IMO measuring the difference may be more work than actually implementing the change. But it would be good to know...
Ceramic coatings could also be applied to main combustion chamber surfaces and piston tops.
PS - I agree that IDIs are vastly underrated by a lot of DI worshipers. :wink: They mistakenly attribute performance benefits as a result of new technology like intercooling and VNT turbocharging technology to the DI combustion process. Well it's pretty clear now after my VNTD 1.6lIDI experiment, that sticking the same turbocharger with an intercooler on an IDI results in equal or greater power output and more broad usable powerband than a TDI, despite the IDI motor being set up to maintain conservative fueling, have less boost pressure than a stock TDI, not to mention the 1.6 liter block has 20% lower displacement than the 1.9l TDI!
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That's the first thing I thought of too, Jake. I'm sure that some of these thermal-coatings that engine builders are starting to use could work well in this type of application. And really, it's such a small surface area involved that I doubt it could add a whole lot of cost to an engine re-build or overhaul. Wasnt there a post a while back about someone taking a test 1.6TD and putting it on an engine dyno and hitting it with as much boost as it could take? I think it was somewhere around 80psi before the prechambers melted out. :P If the prechambers had been thermal-coated, could it have survived? Who knows.
Interesting read, Marc. Nice post! :)
Brendan
84 Scirocco 8v
00 Camaro L36 M49
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This is an argument that has raged with diesel engineers for years. There have been other times when one camp or another has claimed final victory, but the quest always goes on. There have been all kinds of open combustion/DI chambers designed, then there is the Maybach combustion piston, the masked valve turbulence inducers, Caterpillar's combined injector/precup, turbulence chambers of all types, and even the energy cell types. There are all kinds of ways to skin different cats.
As with most engineering problems though, to claim to have come up with the final and best solution is almost always to ask for a smackdown. :wink:
moT
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Andrew,
Performance coatings are def. the wave and if you are seriously interested in having your prechambers coated I'd pop them out and give SwainTech a call and talk to them about the considerations here. They have seemed more than willing in the past to coat just about anything we can throw at them. http://www.swaintech.com or 585-889-2786
I believe this is who did Marc's pistons for his TDI that he rebuilt and this is who is also doing mine.
Marc. That read on the IDI was very interesting and really makes you think about the possibilities for the future. This is def. something that should be further researched and examined. Guess I better find another TD engine to have around for a core since I have an IDI in the family again...NA, but still...can't beat that economy. :)
Joe
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Andrew (and Joe)-
I can vouch for Joe's recommendation of Swain Tech Coatings. Additionally, I have seen the work Stan Wilder's company in Dallas, TX, (www.engineceramics.com) does and can recommend him also.
Stan is a real motorhead, and it shows in the enormous variety of things he has engineered and applied coatings to. And he's a Vanagon nut, too. He's certainly worth considering.
Hope this helps.
-Michael Samson
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Wow, what a great article Marc...thanks! :D
The discussion was excellent as well, and remeinds me of something I've been meaning to ask for a while. Given that we know some of the technologies used in TDIs retrofit very well to IDI engines, what about the IP and ECU? Has anyone seen if the hot combo is an IDI engine electronically injected and controlled?
Think of it...a 7000 RPM engine with whatever hp you want just a chip swap away. :lol: :shock: :twisted:
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Andrew - I have gotten some coatings done from http://www.performancecoatings.com However last time I used them (for moly coating a blueprinted oil pump) they nicked a precision surface of the rotor, then proceeded to jam it into the housing, which scored it irreparable. I wasn't happy with that. You go to all that work and end up with a pump that might be worse than a plain ol' new stocker. :cry: I don't know if they are going downwill or what... I also don't know how confident I am in their internal engine coatings, I've seen some of their coatings applied to valve faces start to pit/flake off. But you might want to compare their prices. I would be confident using them for coating exhaust parts. The pricing you mentioned for all that coating work from Swain seems very reasonable though, and they seem to have a good reputation.
Stan - I have thought about using the TDI electronics on an IDI motor. The thing that would complicate simple swapping the whole works over is that the TDI injector has a lift sensor that is lacking in our IDI injectors... I wonder if one is available. And the software programming might be very proprietary and difficult to accomplish. But all the other sensors, like crank position, MAF, etc seem like they could be adapted. The other way do go about it would be to get the specs on the electronic Bosch VE injection pump and just build your own ECU system from scratch, maybe using Megasquirt DIY standalone injection as a starting point. It would be a real project, but it might end up a lot more easily tuneable and a lot less ungainly than a complete TDI electronic system. Either way, it would be a major project and mechanical governing seems to work pretty well for my purposes at least, so I'll probably just stick to it. They key to getting any fuel injection system working well (whether it be electronic or mechanical) is testing and optimizing.
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You make some good points, Jake. I too had thought of Megasquirt, if only because the VW system appears to have a hard 4500 RPM limit. Lots of issues, to be sure... :cry:
Quick question, does the TDI injector work with IDI engines? I read that TDIs can be retrofited with IDI stuff, but is the reverse true?
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Quick question, does the TDI injector work with IDI engines? I read that TDIs can be retrofited with IDI stuff, but is the reverse true?
Diesel combustion chamber shapes are developed to work well only with only a very specific injector. TDI and IDI injectors are totally different injectors designed for totally different combustion chamber shapes... one being a swirl chamber right in front of the injector, and the other a toroid (donut shaped chamber) that is sort of wrapped around the injector's tip. If you could somehow install a TDI injector in an IDI swirl chamber, it would probably run poorly, and may melt the head around the nozzle tip. Likewise an IDI injector if somehow installed in a TDI's injector hole would probably melt a hole through the middle of the TDI's piston in short order. Neither engine setup would run very well.
The only way I can imagine retrofitting a TDI with IDI injectors is converting it to an IDI entirely by swapping on complete 1.9lTD pistons and head.
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Yeah, I am familiar with the geometries of each head. I was just curious if the IDI injectors are swapped in a conversion to mechanical injection on a TDI. So if not, what do they do, run the lines from the mech IP to the TDI injectors? If so, how are the injectors controlled, since I thought that they are electronic controlled. Or is it the TDI pump that is somehow electronically controlled, and its injectors are still mechanical? That make sense? ;)
Duh, I should know this, but I don't...sorry! :lol:
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Thanks for clarifying Stan, I figured you would have known the difference in combustion chamber shapes! :wink: I'm really glad you weren't confused by some of the threads I've seen on vwhoretex lately... like the guy asking how much better his fuel economy would be on his VR6 if he swapped out his spark plugs for diesel injectors. :cry:
A mechanically governed TDI should definitely maintain TDI type injectors. There is only one that has the lift sensor (and you might notice that it sticks up higher than the other three) and I believe it would probably run just fine with it's electrical connection simply unplugged. For a cleaner mechanically governed TDI pump install, a non-sensored TDI injector could be swapped in place of the sensored injector, but the injector hardline line would need to be re-bent to fit up with the shorter injector, or replaced with a different line that fit right and maintained the same length.
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Got it...thanks Jake! :D
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Well, im very suprise and pleased that this thread brought many reply, only a few days and many reply!!
My first idea was ceramic coating of the pre-chamber. It's easy to remove the insert so they can coat the inside.. I already sent a message to Swain ( that's where my pistons has been coated ) and Rich ask me to send him picture, so that's what i will do, but as he said to me, coating is 'line of sight', so if you can see it, you can coat it..
I sacrificed an 1.6D head for the science this weekend.. So you can see how the prechamber is from the inside. I took a few picture of the pre-chamber alone, with the insert and with an injector, so you can have a good idea.. IMO, polishing the pre-chamber and put a ceramic coating could help us, as well as coat the inside of the insert too, to reflect the heat inside the pre-chamber.. But we'll still loose heat on the top of the chamber ; water in the head flow around the chamber and cool it down..
(http://www.vwdiesel.net/picserv/redrotors/pre1.jpg)
(http://www.vwdiesel.net/picserv/redrotors/pre2.jpg)
(http://www.vwdiesel.net/picserv/redrotors/pre3.jpg)
Some peoples knows that im working since a while on a stand-alone ECU for TDI, lack of time and zillions of other factors made that it's not finished yet, but with the winter coming, i will invest more time on the programmation and testing on the bench. Most of the main subroutines are done and i just have to rig up some electronic to test the IQ ajuster and the electronic timing valve. As you can see on the pictures, i have the electronic "control' of a TDI pump that i took from one of my TDI pump for my testing. This standalone ECU will be "portable" for our IDI. We just have to put a IDI camplate into the TDI pump and voila! we have an IDI electronic pump. Basically, my ECU will 'emule' the mechanical fuel pump. After this basic step done, i will add turbo control, LDA emulation and a better timing control. FYI, Jake, BMW has an IDI injector that fit into our IDI with a needle lift sensor like the 3rd injector on a TDI, so i will order one from europe when then basic ECU will work. I also took a picture of my lab.. :wink:
(http://www.vwdiesel.net/picserv/redrotors/ptdi1.jpg)
(http://www.vwdiesel.net/picserv/redrotors/ptdi2.jpg)
(http://www.vwdiesel.net/picserv/redrotors/shack.jpg)
I hope to keep this subject 'hot' with comments and experimentation results from everyone..
Cheers,
Marc/
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BMW has an IDI injector that fit into our IDI with a needle lift sensor like the 3rd injector on a TDI, so i will order one from europe when then basic ECU will work.
Don't waste your money on the BMW injector, I'll donate one with the needle lift sensor to the "cause". I should have 2 around someplace. The BMW also used timing control similar to the TDI on California models. I have one VE pump housing with the timing control solenoid in it, unfortunately it is a 2 bolt housing, so it won't bolt up to the VW bracket.
I wonder what effect lining the inside of the prechamber with stainless or inconel would have. Almost any nickel or chrome alloy will have far better "insulating" properties than aluminum. The head cavity could be opened up and small cup could be machined and pressed in, then retained by the prechamber insert.
Very interesting to see the propagation of the cracks between the valve seats from the inside, I've always wanted to see one cut in half... :)
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Marc,
Your work/study to date is simply awesome. I love watching these matters get explored with a discerning, scientific attitude. You never know, enough sense made on these threads could attract the eyes of VW engineers - if they knew what was good for them.
Thank you for your work on the IDI ecu - I am VERY interested to hear the result. Such a development would merge my affections for each respective plaform.
This thread came at the perfect time, as I am in serious deliberation between the old and new platforms in building a reliable road-racer. Thankfully 100% veg oil fuel combusts a little more completely, therefore, the prechamber inefficiency is less of an issue. However, the latest idea of a stainless-steel 'thimble' pressed into the chamber with a ceramic coating just sounds good.
In any case, thanks to everyone for the open thoughts.
:shock: laptop tuneable GTD road racer :shock:
-Joey
(1984 merc 300D on BioD)
(1984 Chev G-20 6.2 Diesel on 100% PPO (pure plant oil))
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libby : I used a 'ruban saw' to cut the head.. I removed the valve guide, and the valve seat to save the blade.. It's very easy to cut..
About putting a kinda of shield inside the prechamber has been discussed into the paper i read, with an air gap. I think it's something possible, but perhaps we will have to enlarge the chamber a little in the head to keep the same chamber size..
Bruce, thanks for your donation, i will have something for you.. Plz send me a PM. What do you think about machining the inside of the prechamber to allow the shield to be installed ? Do we need a CNC or a simple milling can do the job ? As you are the expert in machining.. :)
(http://www.vwdiesel.net/picserv/redrotors/crack1.jpg)
(http://www.vwdiesel.net/picserv/redrotors/crack2.jpg)
I took some closeup of the crack for you Bruce.
Marc/
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What do you think about machining the inside of the prechamber to allow the shield to be installed ? Do we need a CNC or a simple milling can do the job ? As you are the expert in machining..
Machining a matching bowl shape into both the head and the insert would be quite difficult. I'm thinking of just a cylindrical cavity in the head, same diameter or slightly smaller than the existing prechamber, possibly with a radius on the top to gain a bit of wall thickness and a cylindrical insert with the hemispherical shape machined on the inside. The inserts would be best cut on a CNC lathe (which I don't have...), or with a radius attachment for a manual lathe. It may be possible to waffle the top and groove the outside diameter to minimize heat transfer to the head. The head pockets could be done with a conventional milling machine. I would probably use the CNC mill just because it doesn't ever screw up (provided the programmer gets it right) and because its the tightest, most accurate machine in our collection of relics... The injector and glow plug holes would have to be drilled through after assembly. Some drill bushings could be made up to screw into the injector/glow plug holes to guide the drills.
Wouldn't be a cheap or easy experiment, but perhaps an interesting one...
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Bruce, Im not sure if i understanded well what you explain, i better understand with pictures sometime.. IMO, we can let the insert as it is, and just coat the inside with ceramic, for the upper part of the prechamber, i dunno how much work it can involve just to make the pocket deeper to allow to put a kinda shield , like the picture i attached. Is it easy to make, an half sphere like that, in stainless or perhaps in Inconel.
(http://www.vwdiesel.net/picserv/redrotors/halfsp.jpg)
And perhaps, to help a bit more, coat in ceramic the inside of the sphere to help keeping more heat inside the chamber.. According to the piece, we can put an half sphere of 1/16 thick w/o any problem.. but we have to shave this 1/16 to keep the size of the prechamber..
You can see in blue where the stainless/Inconel part could be placed..
(http://www.vwdiesel.net/picserv/redrotors/pre1a.jpg)
Marc/
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The half sphere is a very difficult shape to machine. When one side is machined it is not possible to grip the surface so that the other side can be machined. I suppose it could be made by stamping or drawing but that requires presses and dies. Making the outer surface cylindrical allows the "cup" to be chucked in the lathe to finish the inside. Here is the cross section that I had in mind,
(http://www.uploadpixels.com/upload/1130683051_uploadpixels.com_PRECHAMBER_(600_x_469).jpg)
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Wow...this is great stuff, and thanks for donating the head to science Marc! :D
Couple of questions... :lol:
How difficult are the inserts to remove/reinstall? Any special measures? I ask because I will want to coat the upper chamber (blue part) and inside of the insert. Too bad my coating oven isn't large enough for a complete head! :cry:
Is that a photo of the intake or the exhaust port. It looks so clean I want to say intake, but I also want to be sure. ;)
What is that flange I see above the valve seat? Can this be removed for better air flow?
Bruce, if the machining blank is a bit longer, it is easier to make an outside hemispheric cut to complete the bowl after cutting out the inside. The piece might be easier to make on a lathe.
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Stan,
It was an easy job to remove the insert because the head was about to die for science, so i welded a stud on the insert and with an hammerpuller i remove it, it's quite tight. but perhaps you can make an hook thatyou can slide the but output hole of the insert and remove it that way.. I know that 1.9TD inserts are sold, but i dunno about the 1.6..
This is the exhaust port :) , but i cleaned it well.. Im not sure that you can remove the 'flange' you are talking about.. it's where the valve seat, seat on the head..
Bruce, it's a good idea, now i understand.. my only concern is to make 'space' in the head to receive this new part.... but im sure we can figure this thing.. with the collective.. :wink:
Marc/
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this is extremely interesting... I found a website that makes high temperature insulation doing a quick search - http://www.adlinsulflex.com/fire-sleeves/
now I'm pretty sure that would somewhat affect the combustion process, but it would definitely insulate a lot better than ceramic or a coating type product.
the only downside I can see is that it would either absorb some of the diesel + soot, or even some of the compression? (plus making this fabric to fit snug in the swirl chamber and get it to stay would be a feat...)
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Great stuff - that ECU sounds awesome.
I don't think a fabric would last in there. Could be wrong, but I wouldn't do it in my engine. The ceramic coating sounds like the easiest solution. I have done some of that, and with an airbrush, it actually isn't too hard, prep is the important part.
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well the constant abuse the fabric would take will ultimately destroy it eventually, but how long is the question...
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Wow - great work and pics, Marc. :o I've been curious to see what the cross-section of an IDI VW Diesel head looks like. Thanks for saving me the work of cutting one of mine up. Any chance we could see what the cross-section through an intake port looks like? :D
Very interesting to see what the common crack between the valves looks like in cross-section!!
The idea of pressing in an upper pre-chamber insert is interesting, but I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?
Stan: pre-chamber inserts can be driven out by using a punch through the injector hole.
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I have an other slice of the head at home ( one the week, im at the job, 200km far from home and garage ) i wil bring it with me next weekend and i'll post pictures..
I think that first try will be the TBC coating for prechamber and insert, it's the easiest way and see if we can get some improvement.. But i dunno how much ( perhaps in % ) the TBC can reflect heat compare to the bare aluminium...
Marc/
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but I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?
I am unable to find any real information on the thermal conductivity of ceramic coatings. The websites give info in terms of skin temperature drop when used on exhaust headers, virtually no engineering data or hard numbers. Kinda disappointing for an industry that claims to be high tech...
Inconel has a thermal conductivity of 1/10 that of cast aluminum, depending on the alloy. Thermal conductivity of 356 aluminum alloy (typical cast) is 128 W/m K, inconel is 12 W/m K. It is my belief that most ceramics are aluminum oxide based, ALO has a thermal conductivity of 30W/m K or 2.5 times better (worse?) than inconel. I wish I could find figures for the actual ceramic coating...
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I found some data from believe it or not, Greg Raven's book "Water cooled Performance VW handbook". P .32
Zirconium Oxide Coating
Zirconium oxide coating was developed for the space industry. When applied to aluminum it reduces heat transfer, as a result of the lower heat conduction of zirconium oxide (0.53 BTU/hour/feet) compared with the heat conduction of aluminum (139 BTU/hour/feet). The coating is applied using a special process that mixes powedered zirconium oxide with superheated plasma gas that is sprayed onto the aluminum. The coating, which also goes by the name of Turbokoting, is three layers thick, adding a substantial 0.015 to 0.018 inch to the surface.
If you are under budget on your engine work, Turbokoting is for you. Pistons cost about $50 each to coat, and the cylinder head will run about $300. For this reason, I recommend this only for highly stressed turbo motors, and then only if the coating is properly applied.
So far there have been no real problems with the coating flaking off and destroying the turbo (although any coating of this type has the potential for doing so), but it is a good idea to take some 220- or 320- grit sandpaper and lightly scuff the finished coating.
Another reason that this does no get an unqualified okay is that it does not remove of reduce the heat of combustion, it just keeps it from soaking into the coated surface. This heat still has to go somewhere. In a turbo motor, if you can get it all going out the exhaust port you will have better turbo efficiency and better throttle response. The problem is that some of the heat also gets to the rings, the cylinder walls, the valves, and so on.
For less than an all-out motor, you probably will not want to get involved in the research and development it would take to discover the pros and cons of using this coating in your application.
Note that according to the heat conductivity specs, the zirconium oxide coating is 262 times slower to conduct heat than aluminum. So a .015" coating would be equivalent heat conductivity as a slab of aluminum about 4" deep!
So if inconel or stainless had a thermal conductivity 10 times slower to conduct than aluminum, it would need to be .4" thick to match the .015" thick zirconium oxide coating! :shock:
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but I wonder how thick the material would need to be in stainless or inconel to have an equivalent thermal barrier as a ceramic coating would provide?
I am unable to find any real information on the thermal conductivity of ceramic coatings. The websites give info in terms of skin temperature drop when used on exhaust headers, virtually no engineering data or hard numbers. Kinda disappointing for an industry that claims to be high tech...
Inconel has a thermal conductivity of 1/10 that of cast aluminum, depending on the alloy. Thermal conductivity of 356 aluminum alloy (typical cast) is 128 W/m K, inconel is 12 W/m K. It is my belief that most ceramics are aluminum oxide based, ALO has a thermal conductivity of 30W/m K or 2.5 times better (worse?) than inconel. I wish I could find figures for the actual ceramic coating...
Hi
This is indeed an interesting thread...
I did a little research myself into this maybe 6 months ago but I can't remember where I posted.
On thermal conductivity: Al is roughly 210w/m2 /deg K
Steel is approx 50
Granite 2
Glass 0.8
Red brick 0.63
Cement(Lime) 0.3...
So ceramic is probably safely near glass IMO
I argued that ceramic coating would be a good thing but I was shot at by the view that there would be lower volumetric effeciency problems...
I think SHCs of the insulation are a factor in this.
My view point was from the fact that a third of the energy flows round in the coolant and most is from the head and more specifically the prechamber its greatest temperature gradient and large surface area to volume ratio. Then the piston face and main head face with diminishing effects down the walls of the block.
I think I worked out that a 1/4 mm layer gave an insulation of approx 1/3 ... or 2/3 of previous heat passing.
Again someone thought there could be an issue of cold toes in the cab if the main source of heat(the head) was insulated. Hmm... well I think a smaller main radiator could off-set this. :shock:
I feel that quite simply more retained heat in swirl chamber helps combustion and more energy to expand the gasses and so more torque. Thus less fuel needed to reproduce previous heating of gases and hence simply more efficient; with the option of more power.
Of course there is the other third of energy going out of the exhaust; some of which can be recouped by the turbo; but my desire oneday is to utilize the heat to drive a Stirling engine for battery power storage... Ok supplemented with one of those braking energy reclaimers...Dream mode off!!
Anyway that's my 2 pennyworth (4cents :o)
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The coating, which also goes by the name of Turbokoting, is three layers thick, adding a substantial 0.015 to 0.018 inch to the surface.
This is a far thicker coating than the sites I visited offered, and also a different material. Definately the way to go from a thermal standpoint and far less work than inconel liners. Much more expensive than other piston/combustion chamber coatings but if it performs as advertised it would be easily worth the $300 cost. It might allow you to run an 18:1 compression motor and still have it start at -25ēC... :D
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Here are some pictures of different pre cups 935racer collected. The 1.9TD version appears polished because it is brand new unlike the others, which were just cleaned.
Note how small the 1.6TD precup (centre) is in overall diameter and the opening.
(http://www.dieselinside.com/1.6td/prechamber1.jpg)
(http://www.dieselinside.com/1.6td/prechamber2.jpg)
Note how large the opening is inside the 1.9TD precup (far left).
(http://www.dieselinside.com/1.6td/prechamber3.jpg)
Internal volumes:
1.9TD: 5.8cc
1.6TD: 5.2cc
NA 1.6: 5.5cc
For specific dimensions that's up to 935racer to bust out his micrometer.
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Very interesting findings on the prechamber differences... and great close-up pics! Were both of the 1.6 liter prechambers out of hydraulic lifter heads?
I haven't noticed that "dimple" in the face of the 1.6lTD prechamber on any of the solid lifter 1.6lTD's I've had apart before.
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The td is out of a hydraulic lifter head that has never been rebuilt. The other 1.6 was a solid lifter and I have been told it was rebuilt so I am not sure if that precup is stock or not. I have been thinking about porting these cups out a bit to try and get them to flow better, but it seems with every mod there seems to be a negative. I'll dive into the mods this weekend and we can share some ideas, I'll bust out the mics and ive some more accurate measurements later today hopefully. Malone tells me he has a 1.6td solid lifter head that I can bust teh cups out of so I will measure the volume of them as well.
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When I go home I'll edit my pictures to indicate hydraulic or solid lifter head and then re-upload them. A 1.6TD precup from my solid lifter head and a 1.5 precup from a friend's busted motor will eventually be added in the pictures.
We don't have a precup from a NA 1.6 hydraulic lifter head.. well, we don't really need it but if anyone wants to donate one, feel free. It can be used, slightly cracked, doesn't matter.
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Flat side (bottom of prechamber) diameter:
1.9TD: 1.2615" (32.0421mm)
1.6TD hyd: 1.179" (29.9466mm)
1.6 NA solid (rebuilt?): 1.261" (32.0294mm)
I've more measurements, but I need to upload a dimension chart to organize them. Coming soon...
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Basic prechamber dimensions:
(http://www.dieselinside.com/misc/prechamber_dimensions.gif)
1.9TD Hydraulic:
A: 1.0975" (27.8765mm)
B: 1.2615" (32.0421mm)
C: 0.676" (17.1704mm)
D: 0.158" (4.0132mm)
1.6TD Hydraulic:
A: 0.993" (25.2222mm)
B: 1.179" (29.9466mm)
C: 0.677" (17.1958mm)
D: 0.160" (4.06400mm)
NA 1.6 Solid:
A: 1.077" (27.3558mm)
B: 1.261" (32.0294mm)
C: 0.678" (17.2212mm)
D: 0.160" (4.06400mm)
The measurements may not be 100% accurate. i.e. Would VW intentionally change from 1.2615" for one prechamber to 1.261" for another prechamber? Also compare dimension "D" - 0.158" vs. 0.160" vs. 0.160". That's a 0.0508mm difference. So take these measurements as ballpark figures, probably not something you'd take to a machinist right away. The measurements may be enough to help some people figure out a few things though, or at least fulfill our curiousity.
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Great info, thanks! The gas port on the 1.9l precup certainly looks bigger from the picture.
I've got a 1.6lTD solid lifter head out of a car, I can measure the precup OD of (malone's dimension "B").
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The 1.9TD precup has a notch along its outer rim whereas the 1.6TD hydro and NA 1.6 solid precups don't:
(http://www.dieselinside.com/1.6td/prechamber_notch1.jpg)
(http://www.dieselinside.com/1.6td/prechamber_notch2.jpg)
(http://www.dieselinside.com/1.6td/prechamber_notch3.jpg)
Not sure why the notch's there, just thought it was interesting.
Some cracks in the 1.6 TD precup... nothing new but took pictures anyway:
(http://www.dieselinside.com/1.6td/prechamber_crack1.jpg)
(http://www.dieselinside.com/1.6td/prechamber_crack2.jpg)
(http://www.dieselinside.com/1.6td/prechamber_crack3.jpg)
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I too read this thread with great interest. I have a spare warped head and if I can get it straightened, I'm going to port & polish it and I'll certainly consider having the prechambers thermal-coated too. For $100 why not. Coating the piston tops, exhaust valves, ports, and manifold seems a little extreme to me though, unless you were running a TD.
Here's a thought though. If you coated the inserts and the combustion chamber 'bowl' in the cylinder head and trapped all that heat in there, wouldn't that seriously overheat the injector? Wouldn't you want to coat the injector face and heatshield as well to avoid cooking the living daylights out of your injectors?
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Seems like the fuel spray(fog?) exiting the injector may go a long way toward keeping the injector sufficiently cooled.
J.R.
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Fascinating, and lot of great work 'discovering' the truth about these pre-chamber designs by contributors.
Is anyone yet running a ceramic coated pre-chamber?
I was wondering whether a fully polished or ceramic coated exhaust port in the head, would help reduce the temperature differential across the valves, to alleviate the cracking problem, as well as retain more heat in the exhaust gases. This is the first port of call for those hot gases, other than the valve seat, which itself would benefit from slightly better cooling!
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I am running a ceramic coated pre-chamber cup - just the inside of the cup and not the rest of the pre-chamber. I can't tell if it makes a difference. It'd be a good idea to ceramic coat more thoroughly (the entire pre-chamber and other parts of the head like you mentioned). That's what I'd like to do if given the chance.
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To add to Mark Malone's prechamber face diameter measurements, I measured a 1.6lTD solid lifter (from a 1984 Jetta) prechamber face diameter today: 32mm.
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Whatever happened with the discussion that ran some time ago about the piston cutout that was patented by Toyota? Did anyone every try the mimic the same thing?
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That's this thread: http://www.vwdiesel.net/phpBB/viewtopic.php?t=630
"2446" has contributed detailed measurements and pictures there lately, but no one's tried or tested it in a VW IDI motor yet that I am aware of.
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I know that the GM 6.5td (IDI) pistons have this "mod" on thier pistons and I'm pretty sure the 6.2's form the 80's have this too,So its definitely not somthing new.I probably should have done this to my pistons (aaz) but they are ceramic coated now :x too late,mabye I'll do it anyways :twisted:.
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would love to see someone try this...
maybe if i end up picking up that cheap 1.6 rabbit ill look into it...
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I checked with the megasquirt forum and perfect power in Austrila on ecu. Megasguirt is a batch injection setup. It means 1/2 the injectors will squirt at one time and then the other half on the next injector time. Perfect power didn't have anything. (I am on their mail list. I have not asked SDS on their sequensital Injection system) I guy in england is devolping a diesel ECU.
I was looking to do the same thing with the GM 5.7 diesel, which is a IDI system, to get away from the michancial staydne pump.
I always thought the TDI would be better. I have owned 2, a 97 Passat 5 sp, and a 01 Golf automatic. I bought a diesel rabbit new in 80 with a 4sp and while it was not a dog, it sure did lack in power. Nothing like my 2 TDI's
There is a guy on the Vanagon and TDI conversion mail list that converts a TDI injection to a machanicle pump for the TDI. It uses some Fiat parts and parts from the 1.6 diesel and the TDI pump.
Richard
Republic of Texas
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I thought I'd bring this thread back up. I read the patents referenced by the author quoted in Marc's original post that started this thread. Extremely interesting, and completely backs what I understand of the IDI combustion process.
The author apparently works for Daimler-Chrysler in Auburn Hills (at least at the time of the patent filing).
http://patft.uspto.gov/netacgi/nph-Parser?u=%2Fnetahtml%2Fsrchnum.htm&Sect1=PTO1&Sect2=HITOFF&p=1&r=1&l=50&f=G&d=PALL&s1=%206065441.PN.&OS=PN/6065441&RS=PN/6065441
http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F5417189
http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F5392744
http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%%2FPTO%%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F5309879
It appears that a variant of Regueiro's invention can be implemented on the VW IDIs with some machining of the piston crown to extend the flow-guiding "leaves" as Jake calls them and route the outlet of the swirl chamber to the clearance formed by the as yet non-existent valve relief pockets on the piston, rather than to confine the torch of flame issuing from the swirl chamber to the leaves.
The primary advantage of this is, as Regueiro states, to allow piston-to valve clearances that permit timings that are more optimum for breathing and minimized recompression pumping work; and to spread out the flame torch over a larger area on the piston crown for reduced thermal loadings. The issue is that the compression ratio will be reduced, and the key is that this does not adversely affect cold-start and low-speed, low-load operation.
If this can be achieved, the reduced compression ratio will also allow to maintain safe peak cylinder pressures at high-boost levels. Compression ratios of around 19.5:1 on the IDI, if it's adequate for cold-start, etc., would safely support much higher boost levels.
To address cold-start issues with a reduced compression ratio, in reading about the design of the prechambers, I wondered out loud whether someone would have the means to manufacture a ceramic pre-chamber that replaces both the bottom- and top halves. This would reduce heat transfer losses, and give more flexibility of the location and size of the transfer port. I would be happy to offer the design services if someone works in the ceramic sintering industry and can obtain "pucks" as they are called and can get them machined.
Anyone who would like to discuss this is more detail, feel free to shoot me a line at oh.dave (at) gmail dot com.
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I'm a little overwhelmed with the sciences of this thread, but I think between what I've read here as well as in a few other topics, it looks like the "lowly" IDI still has a lot of undeveloped, very promising potential.
Just might have changed my mind from ditching my IDI for a TDI come rebuild time for my "Q"!
If anyone needs it, I've got a bad head (cracked to the w/j in #2) from an MD 1.6TD Solid lifter that I'll donate to research.
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Just might have changed my mind from ditching my IDI for a TDI come rebuild time for my "Q"!
That's what I did.. I had a ALH TDI longblock with a freshly rebuilt head and performance cam.. an upgraded turbo too. I eventually decided to go IDI instead so I grabbed the turbo off the TDI and I haven't regretted it. The power/smoke ratio with the IDI was amazing and there's tons more potential left. The ALH TDI's block has stronger stock internals though, that makes it easier for some who don't want to change everything. Haven't bent my 1.6TD rods @ 37 PSI boost with a flowed head and 100% extra fueling btw. The TDI's main highlights are low RPM torque and fuel mileage.
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The following is a reply I posted in a thread at TDIClub entitled, "DI vs. IDI, interesting article posted on the GTD forum." I thought it would elicit good debate here. :)
http://vwdiesel.net/phpBB/viewtopic.php?t=2329
Basically, to summarize...
An IDI with a VNT and an intercooler actually can be more efficient and powerful than a TDI.
It's just that heat loss problem, and it looks like they're working on fixing that, too.
Apparently the IDIs produce less NOx, too.
Hmm...
Small correction: an IDI can potentially match the performance of the TDI on a displacement basis. But it will always incur a fuel consumption penalty because the inherent nature of the design has greater heat transfer losses and throttling losses though the transfer port between the swirl- and main combustion chambers.
BUT! Going back to performance, the trend in Diesel engine design over the past few years has been to reduce compression ratios for two reasons: the main one has been that increased power ratings of the engines necessitate reducing the CR to maintain peak cylinder pressures to levels that can be withstood by the engine structure. Secondly is that compression ratios have been higher than is actually optimal for best efficiency, in order to offset the need for good cold-starting and low-load, low-speed operation characteristics.
DI can run just fine with CRs down to as low as 16:1. Toyota's 2.2L 180HP D4-D engine has a CR of only 15:8:1. Large truck, locomotive, and marine engines can tolerate even lower compression ratios and have still greater thermal efficiencies than small Diesel engines with higher compression ratios.
On the other hand, IDI, because of it's heat losses, cannot run well at compression ratios as low as DI. There can be some mitigating design solutions, like the use of ceramics and low-heat-rejection, insulating materials around the combustion chamber. Notwithstanding, however, IDI will still need substantially higher CRs, which means for a given peak cylinder pressure (PCP) limit, which is dictated by the design of the engine structure, you will get to a point where the IDI Diesel will hit a wall. Again, this is not because of limitations of the combustion process, but by thermal and gas pressure stress considerations. As far as PCP goes, the current state-of-the-art for automotive engines stands at around 180 - 200 bar. A moderately tuned TDI on the stock compression ratio and slightly increased boost and developing 300 lb.ft. of torque would already achieve these PCP levels. Therefore, in the interest of durability that is expected in an OEM engine, manufacturers would not further develop IDI technology unless there are breakthroughs in PCP or the ability to run lower CRs with everyday performance, driveability and efficiency that customers would expect.
Of course, that's not going to stop the guys like those at vwdiesel.net from pushing the outputs of the IDI engine ever higher. But the state-of-the-art of DI engine development is not sitting still, either. No one 10 years ago would have imagined that a TDI engine you can buy today would have almost DOUBLE the HP (170 vs. 90) from the factory with only a 0.1L increase in displacement, and in modified form be an eyeshot from making 280 HP/400 lb.ft. An IDI would be very hard pressed to reliably match this. 400 lb.ft. with a 22.5:1 compression ratio, and the boost pressure to support the fuelling at this output level, however you slice is, results in tremendous gas pressure forces and PCPs, and would cause some serious pretzel bending of rods among other badness.
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IDI engines tend to be a bit easier on parts than a DI engine of similar power. The throttling effect on the prechamber reduces PCP. The power level required to bend rods in an IDI cannot be fully appreciated unless you have ridden in Andy's car. The cylinder pressures experienced there were no doubt otherworldy, but so was the power. Far, far in excess of any other diesel car I've ridden in. Gerry's TDI pickup would seem positively pedestrian... Also keep in mind that experience has shown that 35-40psi of boost would have destroyed a TDI much sooner. I think it would be safe to say that an IDI can tolerate 2-3 more points of compression than a TDI at the same boost level. Still not likely enough to get reliable sub zero starting and 200hp, but not that far off. Exotic materials for the prechamber and coatings on the pistons and combustion chamber might take it the rest of the way. As usual the only problem is cost, and more cost. A DI engine will still be cheaper to manufacture at high power levels...
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If there's one thing that IDI has a trump card over DI, it is its ability for higher revs.
I also agree with you, Bruce, about everything you say. I would just add that many of the advantages that one design has over the other are the result of the compromises that the design makes at the expense of others. For example, the slower rate of pressure rise in an IDI can result in lower noise, lower NOx emissions and less stresses on the bottom end, but all those things are the direct result of the factors that give DI their converse advantages, namely higher torque, better efficiency and lower other emissions.
As I've said, it's two different ways to skin a cat. Choose the path for what you want to achieve.
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By the way, I'm eagerly hoping and waiting that Andy puts his car up on the track beside Gerry's. Would be very interesting.
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i've been talking to andy about that very thing we're all eagerly awaiting that day!!!! andy needs to haul at least 600Ibs of additional weight so that should make it at least interesting :twisted:
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andy needs to haul at least 600Ibs of additional weight...
Why?
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gerry's caddy, if stock, would weigh in at about 1950Ibs IIRC - his is likely a little fatter with all the trick gear he's rigged up.
andy's tubby golf closer to 2575Ibs, if stock - add an extra turbo, big mother intercooler... :P
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Gerry weighed the truck in at 2400# with him and a 1/2 tank of fuel.
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so about 2200 empty? 400Ibs lighter is probably a safe bet.
hope this happens this summer!
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If there's one thing that IDI has a trump card over DI, it is its ability for higher revs.
Being able to retain torque during high RPM results in more HP leverage. For example, an IDI will only need a paltry 211wtq at 5,000 RPM in order to produce 200whp. The challenge today lies in the fuel pump; it must be able to provide fuel during high RPM without camplate float. Superior Fuel Injection in Ontario will be updating my fuel pump to take care of that. Something as simple as coating the entire prechambers with heat-resistance material (ceramic, etc.) has also yet to be documented on this site. There's much untried potential.
As we already know, the DI intake ports are specially shaped for swirl so there's limited porting/airflow possibilities, which is critical for high RPM.
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a TDI engine you can buy today would have almost DOUBLE the HP (170 vs. 90) from the factory with only a 0.1L increase in displacement, and in modified form be an eyeshot from making 280 HP/400 lb.ft. An IDI would be very hard pressed to reliably match this. 400 lb.ft. with a 22.5:1 compression ratio,
That TDI you speak of is a 16v with improved airflow. Comparing 16v to 8v is apples to oranges. It is not available in NA either. Anyway, to keep the IDI vs. TDI discussion consistent, perhaps it would be better to keep it 8v?
You mentioned daily performance/practicality. 400lb-ft will require a fairly stiff clutch that could reduce traffic/daily driving comfort. The general drivetrain reliability or FWD traction with street tires may also be a concern. A comparible TDI with VE pump and 8v with 200whp is extremely rare here, although we've seen a handful of 170whp 350wtq examples. There hasn't been an IDI with proven 200whp either.. I don't think VW diesel tuning became very popular until the TDI days so there's only a small group of us still tinkering with IDI.
Especially in TDIs, it is easy to have too much torque and not enough HP. An IDI's powerband with peak torque between 4,000 to 5,000 RPM may arguably be more usable in a FWD vehicle used on street and on the track.
The turbo setup used in my 1.6L IDI is in fact the Upsolute Stage III marketed towards TDIs. On a TDI it supposedly dynoed approx. 170whp. With no intercooling, stock cam, and a basically stock block, my 1.6L in a fully loaded 1997 Golf managed to outperform a MK3 VR6 (172hp/155whp). I haven't raced any 170whp-plus vehicles. I also had wheelspin near 4,000 RPM in 3rd on dry, level road, albeit with all-season tires. Unlike the TDI version with the same turbo kit, My IDI had zero smoke in the entire RPM range, with a 9mm pump head and stock injectors. Yes, stock injectors. I don't have hard data like a timeslip as I haven't gone to a track during Winter, but the personal experience left me thrilled.
My next pump update will include a 12mm. Custom fuel injector nozzles were recently acquired from Dieselicous. I am very concerned about the 12mm's RPM limitation, but Superior Fuel said they have some tricks so we'll see. I'm going to have 10mm or 11mm standby just in case.
After the pump's IQ was cranked up to the max, I finally had some WOT smoke below 3,000 RPM. Peak torque was 4,000 RPM. The camplate in the pump started floating at around that RPM, resulting in gradual fuel loss and the torque peak stopped rising.
In case you're wondering, no the 1.6L with the GT20 turbo wasn't sluggish at all during low RPM. It had more get-go than a VW 2.0L 8v gas engine. The GT20 turned out to be too small with too much backpressure. A nice daily driver turbo, but it doesn't suit my max. HP goal. You probably saw the early picture of compound turbos that 935racer set up.
Last fall, my brand new IDI's compression was so low that the engine could not idle on its own unless I revved it and put load on the engine for a minute. The engine still fired up after the 1st crank though, even with a small gas starter motor.
After about 4K or 6K miles and switching from a 3-hole to a 1-hole headgasket, the engine was able to idle on its own during cold start in Winter. I went to Aircare and passed with 2.##% exhaust opacity, below the average passing diesels and well below the 30% limit.
I wonder how much ceramic coating the head will improve cold starts, anyway I daily drove the car at minimum 1 hour 30 minutes each day. I think at that compression (likely in the 350's, below the 412 wear limit) the engine can still handle a lot more power, we'll see.
Heck, very low compression probably isn't needed if I only want to make 211 wheel torque at 5,000 RPM for 200whp. PCP shouldn't be a big concern then, and it'd still do perfectly fine for daily driving.
The wall for IDI performance still remains to be seen :?:
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My 91 jetta weighed 2700lbs with full tank of fuel and two turbos.I susupect the golf 94 golf would weigh a little more but not much.
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The actual weight of the 94 golf with 17's on it could be closer to 2950lbs :shock:.Gerry better have 50 hp more beacuse I sure Have reworked mine considerably from last time and I wasn't far off his power IMO.
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That TDI you speak of is a 16v with improved airflow. Comparing 16v to 8v is apples to oranges. It is not available in NA either. Anyway, to keep the IDI vs. TDI discussion consistent, perhaps it would be better to keep it 8v?
Touche.
You mentioned daily performance/practicality. 400lb-ft will require a fairly stiff clutch that could reduce traffic/daily driving comfort. The general drivetrain reliability or FWD traction with street tires may also be a concern. A comparible TDI with VE pump and 8v with 200whp is extremely rare here, although we've seen a handful of 170whp 350wtq examples. There hasn't been an IDI with proven 200whp either.. I don't think VW diesel tuning became very popular until the TDI days so there's only a small group of us still tinkering with IDI.
Especially in TDIs, it is easy to have too much torque and not enough HP. An IDI's powerband with peak torque between 4,000 to 5,000 RPM may arguably be more usable in a FWD vehicle used on street and on the track.
A TDI does not strictly need to have 400 ft.lb of torque to make 200 HP. This is a choice of the programmer to take advantage of the fact that the DI concept can take more fuelling at low RPMs without reaching the smoke limit. Many people like the driving feeling of having tons of torque down low; others only like driving high-revving gassers. I'm somewhere in between.
If a hypothetical TDI could produce 211 lb.ft of torque at 5000 RPM (not saying it has or can be), you know that you can make the rest of the torque curve almost look like anything you want (within limits), like that of an IDI or a broad straight line like a 2.0T gasser. But that squanders all the low-end torque potential that the TDI has.
At the end of the day, it's a preference thing of the driver, and as I've always championed, you make your choices on what suits your preference.
The turbo setup used in my 1.6L IDI is in fact the Upsolute Stage III marketed towards TDIs. On a TDI it supposedly dynoed approx. 170whp. With no intercooling, stock cam, and a basically stock block, my 1.6L in a fully loaded 1997 Golf managed to outperform a MK3 VR6 (172hp/155whp). I haven't raced any 170whp-plus vehicles. I also had wheelspin near 4,000 RPM in 3rd on dry, level road, albeit with all-season tires. Unlike the TDI version with the same turbo kit, My IDI had zero smoke in the entire RPM range, with a 9mm pump head and stock injectors. Yes, stock injectors. I don't have hard data like a timeslip as I haven't gone to a track during Winter, but the personal experience left me thrilled.
Nice, I look forward to see some dyno numbers. I have ridden in some fiercely quick TDIs as well, including Gerry's truck. After all the hearsay, a dyno plot -- for all its questionable-ness -- is still the one way we can compare apples-to-apples. Gerry is arranging on a dyno day likely in June, and I'm excited to see what if anything the cam I designed does in his ride.
My next pump update will include a 12mm. Custom fuel injector nozzles were recently acquired from Dieselicous. I am very concerned about the 12mm's RPM limitation, but Superior Fuel said they have some tricks so we'll see. I'm going to have 10mm or 11mm standby just in case.
After the pump's IQ was cranked up to the max, I finally had some WOT smoke below 3,000 RPM. Peak torque was 4,000 RPM. The camplate in the pump started floating at around that RPM, resulting in gradual fuel loss and the torque peak stopped rising.
I posted a long time ago expressing my interest to see what Giles could do with the electronic VE TDI pump. I have a brand-new AHU pump with one of Marc's 12mm heads that's sitting 7000 km from me in Gerry's garage. The offer now is the same as it was before: I'd gladly donate that pump to Giles (or anyone for that matter) as his development mule for him to work his magic on it. Between Gerry and I, the cost will not be in issue when it actually does something.
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The actual weight of the 94 golf with 17's on it could be closer to 2950lbs :shock:.Gerry better have 50 hp more beacuse I sure Have reworked mine considerably from last time and I wasn't far off his power IMO.
Andy, we all look forward to the showdown, whenever it should happen (hopefully very soon!) :lol:
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My project is coming along pretty slow lately :x .However things are starting to come together now,with the only issue being that I want to do some back to back testing of cams and 12mm vs 9mm heads. This was all planned to happen after the engine actually runs which will be a while yet.I could have just slapped the stg 3 cam and 12mm head in there but with lowering the compression,changing turbos,car etc...I need to see what things are doing when changed one part at a time.
Anyhow nothing like a good old IDI/TDI showdown.BTW we still need to talk Gerry into getting a proper(quick reacting) EGT gauge and have it reading the temp before the turbo.I know his EGT's are not sustainable in the 1/4 mile.Honestly,I'm just concearned about his engine and not about bashing his egt gauge.
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Anyhow nothing like a good old IDI/TDI showdown.BTW we still need to talk Gerry into getting a proper(quick reacting) EGT gauge and have it reading the temp before the turbo.I know his EGT's are not sustainable in the 1/4 mile.Honestly,I'm just concearned about his engine and not about bashing his egt gauge.
Yes, I totally agree that you two need to get into more dialogue. :) I believe you two will mutually benefit and great things will come about if you two are putting your collective heads together. Nothing will give me more pleasure than to have braggin rights to the fastest Diesel (TDI or IDI, doesn't matter) in Canada as opposed to the European -- particularly British -- threat :lol: I talk to Gerry very often, and we spent Easter in Holland and the following weekend in Germany when he came for a European vacation.
Pictures (http://forums.tdiclub.com/showthread.php?t=137181)
As for the EGT issue, the three main contributing factors to EGT are 1) if combustion duration is extended due to retarded start of injection timing or extending the end of injection to increase fuelling; 2) if you're running insufficient boost for the given power output; 3) running a poorly matched turbo and poor- or no intercooling.
Anytime we're talking about engines making double or more of the rated factory output, sure you're running much higher thermal and mechanical stresses, and it doesn't matter if the engine is DI, IDI or gasser. I'd like to hear what is your rationale for your concern for the EGTs in Gerry's motor.
I would argue that a highly rated IDI has greater issues concerning blown head gaskets and such (the components affected by the high PCPs), and the invisible killer that is the thermal stresses, particularly manifested by cracks in the area of the swirl-chamber and the valve bridge. You can only imagine the immense heat fluxes that are occuring in the chamber and transfer port.
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First off.. TDIMeister, the wife an I want to know if you're avaliable as a guide? Fantastic photos! Where are these museums located? We were in Germany 15 years ago for only 18 hrs (Navy training flight where we couldn't convince the Plane Commander that the plane still shouldn't be flown yet :roll: :( ). We flew into Rhein-Main AB outside of Frankfurt, "borrowed" a car :mrgreen: and drove to see an old friend at Sembach AB outside of Kaiserslautern. We DEFINITELY wanted to stay and see more! If things go well, maybe in the next year or two 8) .
Anyway... back on topic, heres my dumb question :oops: ... How does air get into the prechamber to start the ignition process and what effect would it have if you were able to get more air in there?
Alain
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Thank you for the compliments, Alain. Yes, I'm available as a guide :) It was actually something I thought of doing during my holidays from studies. Alas, I have no real holidays to speak of, but I will post more pics from an upcoming 2-week, 8-country European road trip :D
Anyway, air simply flows anytime there is a pressure difference. In the simplest explanation, it's by the same phenomenon that we experience wind (because of differences of local atmospheric pressure; of course there are other effects, like heating convection from the sun, etc.). In an engine, the moving piston displaces the air that is trapped in the cylinder and increases the pressure. Because of the property that air is a compressible gas, it takes a finite amount of time for the pressure to equalize throughout the trapped volume, so until that time, there is a flow of air molecules from a region of higher pressure to one of lower pressure.
If you get more air in a volume, whether an engine cylinder or anything else, it simply means that you trap more air molecules (specifically the oxygen component of that air), that's available to burn more fuel. That's what turbos do: pre-compress the air before it goes into the engine so that you have a greater amount or mass of air to burn more fuel to get more power.
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The VDO EGT gauge that Gerry is/was using was really slow reacting,others would agree.A vdo egt gauge is good for a transport truck pulling up a hill where it does't need to be quick reacting unlike our race engines that pump out lots of heat real quick.Also with the probe being installed far from the turbo outlet on the downpipe this would lower the egt probably 325-350 deg.
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I'm sorry for my vague question. What I was wondering was, what effects would there be to the pre-chamber and ignition quality, if a way was found to get more air into the pre-chamber? Would it defeat the purpose of the pre-chamber (speed control of ignition, as I understand it)?
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Would it defeat the purpose of the pre-chamber (speed control of ignition, as I understand it)?
The purpose of the prechamber is to improve the speed and the quality of charge mixing. The extreme turbulence generated in the prechamber is what allows an IDI engine burn cleanly and produce good torque at high rpm. The prechamber has a side effect of reduced combustion noise due to the softer pressure rise in the main combustion chamber.
If the prechamber orifice size was increased high rpm power might improve. This would probably come at the expense of low rpm power/smoke and idle quality. It would also increase engine noise. Everything is a tradeoff...
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the fact that the DI concept can take more fuelling at low RPMs without reaching the smoke limit.
Shouldn't that advantage be attributed to VNT technology, not DI technology? Although VNT has been tested on an IDI with a broader powerband as a result (more low RPM torque and more high RPM torque with less boost), the VNT diaghram must be modified to function mechanically.. so it might be fair to credit DI for the advantage of being able to produce more low RPM torque with less smoke (assuming it has VNT turbo, of course).
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Mine and many wastegated TDIs have quite a pronounced torque hump at the low end :)
More broadly, if you look at the vast collection of DI and IDI Diesels over the years, VNT or wastegated, the torque curves look distinctively different. IDI has a lower peak that is held in a narrow torque range over a wider speed range, and extends to a higher RPM. Most DI I've seen have very big torque peaks at low RPM, have nearly constant HP over the last 500-1000 RPM before the peak, and drops off steeply at a lower RPM than IDI.
There are many contributing factors for this, but I can't guess as to which one or two are dominant.
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If a hypothetical TDI could produce 211 lb.ft of torque at 5000 RPM (not saying it has or can be), you know that you can make the rest of the torque curve almost look like anything you want (within limits).
Definitely.
A few months ago a US resident with an ALH TDI contacted me about driving up to BC this Summer to get custom chipped. With a VNT-20 turbo he wants good driveability and drivetrain reliability so he requested a maximum of 275 wheel torque. I took an existing TDI dyno graph and drew dotted lines to simulate his request:
(http://x11.putfile.com/1/1814514499.jpg)
(the final torque curve will not be exactly the same)
The VNT-20 is a good choice in this case because not only it is still capable of producing his requested torque below 2,500 RPM, it will continue to flow more air than smaller VNTs. Good for retaining a little more torque (and HP) up until redline. Lower EGT, too.
If a hypothetical TDI could produce 211 lb.ft of torque at 5000 RPM
A 211wtq @ 5,000 RPM IDI is still more plausible than a TDI performing the same. The IDI has higher combustion efficiency at higher engine speeds with lower amounts of air required per cycle at the same smoke level. 10-15% more power at the shaft according to the document quoted in the first post.
While it is easily proven that a modified IDI can produce enough low-RPM torque to cause initial wheelspin, who said that must be sacrificed for more HP in the top end? That's where compound turbocharging becomes useful to cover a wide RPM range, if not a VNT.
A gasser-like transmission could be used for a 6,000 RPM IDI and the close gear ratios will amplify low-RPM torque. An IDI's powerband seems more manageable for a FWD vehicle and it will help be more competitive against gassers. Some people overlook the importance of RPM and HP. Regardless, like you said:
At the end of the day, it's a preference thing of the driver, and as I've always championed, you make your choices on what suits your preference.
I agree totally. I will be buying a 2006 MKV Jetta TDI soon for daily driving while my IDI goes under the knife. I'll enjoy the fuel economy and if I want to modify it further I intend to make it torque monster :)
If I had to choose between a TDI and IDI, both with limited redlines (5,000 RPM).. I'd probably lean towards the TDI. Otherwise a high-RPM IDI theoretically has more HP potential.
Nice, I look forward to see some dyno numbers.
Me too.. after the IDI goes back on the road I will definitely go on a chassis dyno :)
After all the hearsay, a dyno plot -- for all its questionable-ness -- is still the one way we can compare apples-to-apples.
Agreed.
I posted a long time ago expressing my interest to see what Giles could do with the electronic VE TDI pump. I have a brand-new AHU pump with one of Marc's 12mm heads that's sitting 7000 km from me in Gerry's garage. The offer now is the same as it was before: I'd gladly donate that pump to Giles (or anyone for that matter) as his development mule for him to work his magic on it. Between Gerry and I, the cost will not be in issue when it actually does something.
Perhaps I can talk to him about that after he finishes my IDI pump.
If Giles raises the physical max. timing in the VE TDI pump, and if Gerry needs adjustments in his ECU to take advantage of the new timing range, then let me know as I believe I'm capable of doing that.
Cheers,
Mark
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Mine and many wastegated TDIs have quite a pronounced torque hump at the low end :)
More broadly, if you look at the vast collection of DI and IDI Diesels over the years, VNT or wastegated, the torque curves look distinctively different. IDI has a lower peak that is held in a narrow torque range over a wider speed range, and extends to a higher RPM. Most DI I've seen have very big torque peaks at low RPM, have nearly constant HP over the last 500-1000 RPM before the peak, and drops off steeply at a lower RPM than IDI.
There are many contributing factors for this, but I can't guess as to which one or two are dominant.
1) There are a fair number of 1.9 IDIs with K14 and T2 turbos that are larger than the wastegated turbos found on 1.9 TDIs. The larger turbo builds boost more slowly. However, I have not seen a dyno plot of a stock 1.9 IDI with a K03 turbo so you could still be right.
2) The TDI's higher injection pressure likely contributed to the low RPM combustion performance, although stock IDIs with low injection pressures are irrelevant in this type of discussion. There may be a difference in an IDI's low RPM torque:smoke ratio if its pump is upgraded to 10mm or 11mm, and perhaps have its camplate upgraded as well.
Other than these, I'm not too sure how much the DI combustion process itself contributes to the added low RPM torque.
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I would think that the lower CR would allow better low rpm efficiency
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2) The TDI's higher injection pressure likely contributed to the low RPM combustion performance, although stock IDIs with low injection pressures are irrelevant in this type of discussion. There may be a difference in an IDI's low RPM torque:smoke ratio if its pump is upgraded to 10mm or 11mm, and perhaps have its camplate upgraded as well.
Has anyone experimented with higher injection pressures on IDI's and if so, what were the effects, the limits and how much effect on actual timing?
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Bump for refreshing:.....
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I would think that the lower CR would allow better low rpm efficiency
No, it would make it particularly worse. At low-load and low-RPM, heat losses are especially high, because there's simply more time for heat transfer to occur to the cylinder walls. Less trapped mass also loses heat faster (compare seasonal temperature variations between Lake Superior and Lake Erie, for example). Therefore the cylinder charge cannot get up to an optimal temperature to combust the fuel, and thermodynamically, heat loss simply represents wasted energy.
In theory, thermal efficiency increases continually with increasing CR, but in practise, the thermal efficiency to CR graph flattens out at a peak and falls off as well due to other losses. And the "optimum" CR is below what is common practise on most Diesels to offset the need for good cold-start and low-load efficiency.
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I haven't used their products, but check out the website... ceramic metalic bake at home coatings..
http://www.techlinecoatings.com/
I also posted in this thread about toyotas notched chamber , I'd be willing to do some machining.
http://www.vwdiesel.net/phpBB/viewtopic.php?p=33214#33214
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A very enlightening discussion, including the toyota piston digression.
What about anodizing (a thick alumina layer produced with electrochemistry)
prechamber, PC insert and piston
?
It should reduce heat transfer and -I think- is the most durable.
It's probably the most do-able with the least equipment.
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anodizing wont really make any kind of heat transfer difference.... there are some ceramic coating techniques which may be used for this application which would dramaticallydecrease heat transfer through the pre-chambers, and I will be looking into this and experimenting with it in 2007.
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Hi,no one has mentioned keeping the chambers warmer by activating the heater plugs on say half voltage all the time the engine is running,so adding heat,peugeot diesels here in the u.k have there heater plugs activated for at least 1 minute after starting to stop any smoke.This will cause more drag off the alternator,but if for racing have a slave battery fitted just for the glow plugs post starting,and manually charge it at home or have a switchable split charger,switch on after racing :twisted:
Might be a crap idea?
Bert
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All very interesting stuff, even the stuff that was beyond me... As someone with a 1.6N/A IDI that may need a rebuild this is all stuff that could be of some use to me. Am I just waking the dead bumping this post, or has there been progress with improving the efficiency of the IDI in the last few months?
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I juste finished reading the WHOLE POST !!!! :shock: It took me almost 1h30 but it was worth it ! :D I am going to be rebuilting a 1.9 TD in a couple of weeks to go in my 1992 Jetta. I wanted to know if someone had tried the ceramic coating ???? Because i would be very interested. But some guys talked about ''too much heat for the injectors''??? Is that a probleme ??? Because this motor will be in my daily driver, so i want the motor to be reliable (thought i want it to be powerful :wink: ). So if anyone as more info on the ceramic coating, i would be interested on maybe testing it on my 1.9 TD. So thanks everyone for this great post, it is very interesting. I'll be waiting for your reply.
Alex
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Hi,no one has mentioned keeping the chambers warmer by activating the heater plugs on say half voltage all the time the engine is running,so adding heat,peugeot diesels here in the u.k have there heater plugs activated for at least 1 minute after starting to stop any smoke.This will cause more drag off the alternator,but if for racing have a slave battery fitted just for the glow plugs post starting,and manually charge it at home or have a switchable split charger,switch on after racing :twisted:
Might be a crap idea?
Bert
[/size]
Nothing wrong with a crap idea... Better than no idea at all. Would it be of any benefit? H'mm Why not raise compression to raise the heat homogenously ????sp! Both methods add load to the engine... or do they :wink:
Would this paint work as a ceramic substitute?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=003&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=130022011795&rd=1&rd=1
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Um no, that stuff wouldnt even stay on the outside of the manifold let alone inside the combustion chamber.
dan
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Um no, that stuff wouldnt even stay on the outside of the manifold let alone inside the combustion chamber.
dan
[/size]
Hmm just found this site...
http://72.10.43.141/high_temp.htm
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This article describes many of the differences between DI and IDI. The author seems to think that our little old IDI is superior in many ways!
http://www.patentstorm.us/patents/5915351-description.html
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Um no, that stuff wouldnt even stay on the outside of the manifold let alone inside the combustion chamber.
dan
[/size]
Hmm just found this site...
http://72.10.43.141/high_temp.htm
Well give it a try and let us know how it works will ya?
From experiance I will say even 1500 deg paint isnt going to stick on the exhaust housing for long.
dan
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I found that mud from Moab stays on very well. :P
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Oh yes, it sure does. I have a nice set of Thorley headers with Brown spots all over them :roll:
dan
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Oh yes, it sure does. I have a nice set of Thorley headers with Brown spots all over them :roll:
dan
Yeah what's up with that? I keep wire brushing and re-painting some spots on the frame of my Jeep but it keeps coming off every few months. There's still mud under there from my first off-roading that will refuse to come off even with a pressure washer!!! :P
Brendan
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What was the final result of the ceramic coating research? Did anyone actually coat the prechamber and the upper part of the chamber in the head?
(There's lots of reference to ceramic coating and prechambers on this site but noting definitive.)
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awesome stuff, definitely keeping an eye on this thread.
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Keep watching, but the last time this thread was active was 5 years ago.
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I remember a few threads of people who coated the pre chambers and everything. I think there is probably alot to be gained from coating inside the swirl chamber but only on the round part in the head, not on the inside of inconel cup itself. I think that would help keep the heat as a part of combustion instead of being wasted in the coolant. Then obviously coating valves pistons and combustion surface on the head would help with all that too woot
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Yeah that thread I bumped I think it was Malone's old IDI had coated inner precups. His findings were that if you coated the inner it wouldn't have enough residual heat and it always smoked whitish. Like this it was an old thread that I bumped, but on purpose to show the younger ones what had been done.
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I wish the old forum was still available. I think a glimpse of it is available through the way back machine. Alot of good info was there, even going back to the early days of the switch to this new forum which is only a few years from being a decade old!!!
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Keep watching, but the last time this thread was active was 5 years ago.
something i keep forgetting about this forum, the activity is quite low, however the quality of threads is much higher. Other forums i follow are much much more populated and constantly changing.
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Be warned, ceramic coating will stop heat from penetrating it's surface.
That heat still has to go somewhere. It won't get dissipated via oil cooling through the piston.
DCR's making 4 digits on 2.4L, no thermal coatings.
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Well, I did not use any coatings.
On my 1.6 TD, I opened up the port in the swirl chamber cup, disabled the wastegate, disabled the blowoff valve, lowered the compression ratio, and increased the fueling rate. Now, the engine makes 88 HP at the wheels (measured on a dyno). Stock turbo, no intercooler. The old rubber hose from the turbo to the manifold could not handle the increased pressure (25 psi), so I made a steel elbow to replace it.
What are the HP losses of an 020 transaxle and the tires at 60-70ish MPH? Perhaps 12 HP? If so, then the 1.6 TD is making around 100 HP at the crank.
A 1.6 TD will run when the compression ratio is 17.5:1, but it REALLY needs for the timing advance knob to be pulled out until the engine is almost up to operating temperature.
I built this engine for my racecar and had expected to get about 100 HP at the wheels (about 110-115 at the crank), but it did not work out.
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Add an inter cooler, lower the boost a bit (20ish) and up the fuel a bunch.
There is a ton more power to be had if you aren't even inte cooled yet. Might I ask why you lowered compression? Is it because of the addition of a 1.9 AAZ head?
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Actually, the head is an original from a 1.6 TD, just rebuilt. :-)
I lowered the compression ratio in order to reduce the peak cylinder pressure. The crack between the valves in the head on one of my other 1.6 TDs cracked all the way into the water jacket (the engine was stock all its life). As far as I know, all these heads do this, it is just a question of time. My guess is that the lower peak cylinder pressure will slow the crack propagation.
Yes, I could add an intercooler, however that would be a major undertaking. Besides, there is no really good place to mount it. Putting it in front of the radiator would reduce the effectiveness of the radiator...
While an intercooler would reduce the boost pressure, it would also throw away heat that I would rather have go into the cylinder. (An engine is just a device to convert heat into energy on the shaft, the higher the peak temperature, the better it works.)
The fueling rate screw is turned in far enough that the collar is against the locknut, and the heat rejection rate of the engine is enough to overload the cooling system on a warm day. Being in a racecar the engine spends almost all of its non-idling time at wide-open throttle. My suspicion is that the engine is not far from maxxed out.
I think I will get more bang for my buck to take the 1.6 out of the racecar, and install a TDI instead. Then, install the 1.6 in a street-use vehicle (putting the compression ratio back to stock, and lowering the fueling rate to something reasonable).
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Actually, the head is an original from a 1.6 TD, just rebuilt. :-)
I lowered the compression ratio in order to reduce the peak cylinder pressure. The crack between the valves in the head on one of my other 1.6 TDs cracked all the way into the water jacket (the engine was stock all its life). As far as I know, all these heads do this, it is just a question of time. My guess is that the lower peak cylinder pressure will slow the crack propagation.
Yes, I could add an intercooler, however that would be a major undertaking. Besides, there is no really good place to mount it. Putting it in front of the radiator would reduce the effectiveness of the radiator...
While an intercooler would reduce the boost pressure, it would also throw away heat that I would rather have go into the cylinder. (An engine is just a device to convert heat into energy on the shaft, the higher the peak temperature, the better it works.)
The fueling rate screw is turned in far enough that the collar is against the locknut, and the heat rejection rate of the engine is enough to overload the cooling system on a warm day. Being in a racecar the engine spends almost all of its non-idling time at wide-open throttle. My suspicion is that the engine is not far from maxxed out.
I think I will get more bang for my buck to take the 1.6 out of the racecar, and install a TDI instead. Then, install the 1.6 in a street-use vehicle (putting the compression ratio back to stock, and lowering the fueling rate to something reasonable).
they all crack, but they don't all crack to the water jacket, that is actually pretty rare. how did you lower compression? i hope you didn't stack head gaskets.
i think you have all the wrong ideas about intercoolers and how heat in the engine works. it will reduced boost pressure but you will actually be getting more air because all the air molecules will be closer together rather than hot more excited and spread out, your radiator won't have as much work to do if the engine isn't ingesting a bunch of super heated air. also with an intercooler the exhaust side of the turbo has to do less work to move the same amount of air, so that creates less back pressure and lower egts. also closed waste gate is no good for efficiency. your engine is far from maxed out its basically stock with slightly increased fueling and lots of boost. u haven't even upgraded theintake manifold
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i had almost 140hp at crank from a 1.6d with k24,intercooler and added fuel.just that, so you are very far from maxxed out.
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rabbit_tdi -
introducing heat to the engine before combustion wont get you any power. The engine only makes power during the power stroke, after ignition of the fuel. If you 'add heat' before this, you are only reducing the maximum amount of power that you can produce, because you decrease the difference between the operating temp and the 'effective ambient' temp.
If you were to add a good intercooler setup, you will see lots more power and much better efficiency. trust me, Im an engineer :-)
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your engine is far from maxed out its basically stock with slightly increased fueling and lots of boost. u haven't even upgraded theintake manifold
i had almost 140hp at crank from a 1.6d with k24,intercooler and added fuel.just that, so you are very far from maxxed out.
Yup, and Yup. In fact, with the lower compression ratio I'd take a stab to say that you are extremely close to stock power levels if not below it. You have lowered compression so that you can run gobs of boost without the supporting fueling, you probably still have the same cylinder pressures as before.
Basically what you have said to us, is that you have made your engine almost as inefficient as possible. LoL.
Trust me, I am an engineer :-)
This man knows! lol
You want the air to be as cold as physically possible when entering the cylinder, now being SUPER HEATED to that much boost pressure is not the way to do that.
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i had almost 140hp at crank from a 1.6d with k24,intercooler and added fuel.just that, so you are very far from maxxed out.
How did you measure HP at the crank on a dyno? ???
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i had almost 140hp at crank from a 1.6d with k24,intercooler and added fuel.just that, so you are very far from maxxed out.
How did you measure HP at the crank on a dyno? ???
dynos in portugal measure power to the wheels and crank.pretty sure is an estimate.
almost 120 at wheels.
(http://img181.imageshack.us/img181/5528/thwt004fs4.jpg)
how did you lowered compression?
i want to know how to increse it(1.5+1.6.1.9 idea)
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engine dynos are common. You can bolt an engine to it and measure it right from the crank.
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engine dynos are common. You can bolt an engine to it and measure it right from the crank.
Do you take the engine out and bolt it to the dyno or is it done with the dyno bolted to the engine while in the car?
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Engine needs to b on test stand.
(http://www.unitronic-chipped.com/imgs/photos/big/engine_dyno.jpg)
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That's a big job to pull an engine to put on a dyno, unless it was freshly rebuilt. I wonder why carrizog60 reported the estimated crank hp rather than wheel hp when it was done on a wheel dyno?
ps.
I had my 92 Eco on a dyno a month ago and the TQ at the wheel was 103 ft lbs @ 2800 rpm and 62 HP @ 3300 RPM. Everything stock except governor mod.
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That's a big job to pull an engine to put on a dyno, unless it was freshly rebuilt. I wonder why carrizog60 reported the estimated crank hp rather than wheel hp when it was done on a wheel dyno?
ps.
I had my 92 Eco on a dyno a month ago and the TQ at the wheel was 103 ft lbs @ 2800 rpm and 62 HP @ 3300 RPM. Everything stock except governor mod.
In Europe that is how they normally do things
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ps.
I had my 92 Eco on a dyno a month ago and the TQ at the wheel was 103 ft lbs @ 2800 rpm and 62 HP @ 3300 RPM. Everything stock except governor mod.
Didn't you remove the cat ?
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I wonder why carrizog60 reported the estimated crank hp rather than wheel hp when it was done on a wheel dyno?
In Europe that is how they normally do things
yep,here normal is rate and engine by engine horsepower,not wheel hp.
so,what about the compression thing?gathering info on 1.5 guts on 1.6 block and 1.9 head.
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Oh, I forgot to mention earlier there is another reason that I lowered the compression ratio.
Initially, I did run the engine at the stock compression ratio (with high boost and a heavy fueling rate). After 10-20 hours of hard use I noticed dried coolant at the head gasket joint. I interpreted this as the peak cylinder pressure being enough to lift the head just enough to let a little coolant out during operation. There was no leakage during the weeks the engine was not running.
After reducing the compression ratio, and keeping the same boost and fueling rate, I had no more dried coolant at the head gasket joint. :-)
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Did you ever answer the question on how you lowered compression while still running 1.6 head?
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Did you ever answer the question on how you lowered compression while still running 1.6 head?
nope
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Did you ever answer the question on how you lowered compression while still running 1.6 head?
He probably just ran the next notch up head gasket. His logic on his reason for doing it does seem sound; I would have tried hylomar and head studs, but as long as he didn't have hard starting, smoke at cold idle, or noticeable power loss then he found a way to solve his problem cheaper than the route I'd take, and just as effective.
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Did you ever answer the question on how you lowered compression while still running 1.6 head?
He probably just ran the next notch up head gasket. His logic on his reason for doing it does seem sound; I would have tried hylomar and head studs, but as long as he didn't have hard starting, smoke at cold idle, or noticeable power loss then he found a way to solve his problem cheaper than the route I'd take, and just as effective.
its been proven many times that running the wrong head gasket does not effectively lower the compression while still retaining good power and low smoke at cold idle...
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According to the manual, the piston protrusion calls for a 2-hole head gasket, which would give a 23:1 compression ratio. My calculation indicated that a 3-hole gasket would give a 22.4:1 ratio.
Realize that initially I had no idea how low the compression ratio could be, and the engine still be able to start. So, I did not want to make any expensive changes, and only changes that could easily be undone; this eliminated my considering machining the pistons or the head. The cheapest thing I could think of was to increase the distance between the head and the block, so I did; the original head gasket was .059", the replacement was/is .110". My calculation indicates the resulting compression ratio is 17.5:1. As it happens, the timing belt was just barely able to slide on to the sprockets; it needed very little rotation of the idler to properly tension the belt.
I recommend AGAINST the 17.5:1 compression ratio for use on the street. This engine of mine is NOT used on the street, and does not need to start below freezing. When starting it, I keep the timing advance knob pulled out until the engine temperature is up to about 140-160*F or so, in order to smooth the idling and reduce the white smoke. Also, the engine does have an electric block heater, which I use if the temperature is below about 45*F. Of course, the glowplugs are necessary. When the engine is up to operating temperature, it runs nicely and does what I expect.
When I remove this 1.6 TD engine and then put it in a street-use car, I will restore the compression ratio to 23:1, and reduce the fueling rate to something from which I will expect a reasonably long life. :-)
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My dad has a well used 1.5D is his mk1. He has rebuilt it a couple of times and the pistons have been out on numerous occasions... anyway, basically he's using on it a 4 notch gasket (which is pretty uncommon in the states I believe) but you can get them... anyway its very thick. Not necessarily the correct thickness.
Anyway, he has a lot of trouble starting the car compared to all my VW diesels - and he blows a lot of white smoke when cold (Actually just a lot of the time).
All my engines have the right headgasket :-)
I ran the calcs on rabbit_tdi's numbers and I would agree you compression must be down around 17.2:1. Pretty low for an IDI but not unheard of by any means for a standard engine. There are some older toyota precombusiton chamber diesel that have a 17:1 compression ratio as standard. Those engines go forever but they are not at all powerful and they get poor economy.
With your static compression ratio so low, I think you could afford to advance the timing a lot more than you otherwise might.
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on the other side how could i increase the compression?
using a 1.5 guts on 1.6 block and 1.9 head.
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on the other side how could i increase the compression?
using a 1.5 guts on 1.6 block and 1.9 head.
Only thing I could really think of is having the precup areas filled and remachined to fit 1.6 cups. Or just run a 1.6 head that's ported. Or just do a 1.6 with 1.9 head haha. I think that small amount of displacement is more valuable than any gained rev ability from 1/8" shorter of a stroke. How ever the weird factor makes some setups more desirable
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on the other side how could i increase the compression?
using a 1.5 guts on 1.6 block and 1.9 head.
Only thing I could really think of is having the precup areas filled and remachined to fit 1.6 cups. Or just run a 1.6 head that's ported. Or just do a 1.6 with 1.9 head haha. I think that small amount of displacement is more valuable than any gained rev ability from 1/8" shorter of a stroke. How ever the weird factor makes some setups more desirable
why does everyone want to build a 1.5/6/9 now all the sudden?
the 1.6 bottom end is good for whatever RPM we can throw at them..
THERE ARE NO GAINS TO BE HAD WITH A 1.5 ROT. ASSY.
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Also as I found with my last engine being a 1 notch but still not in the range it should have been the fuel doesn't burn right. The compression is lowered, but I think the flame travel is elongated and what gave me the EGT issue I had. It compression retards timing, so you throw more to it to mask the problem and then you get hot spots. This is all theory, but my engine grenaded because of precup failure and I have traced it back and guessed/reguessed and this is the best answer I have. What is safe compression ratio??? I don't have a concrete answer, but I think if you had around 19 even you would have the best of both worlds.
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I think the pre cup has to be the right height from the piston for combustion to work properly
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I think the pre cup has to be the right height from the piston for combustion to work properly
yes...at least that is what my feeble mind has came up with and I call it flame travel. When it is too far away instead of swirling in the precup and then to the piston and then out the ex. valve. It has room to leave and go to the space between the head and piston. Leading to incomplete portions of the diesel not burning as it isn't compressed or quenched enough. So you advance it to help the problem and you get more of the same just hotter hotspots. Right now it is just my theory and I cannot accurately prove it 100%, but I won't mess around with it ever again theory or not.
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wanted that combo for werd factor lol
what is the diference in adding the 1.5 equation to the 1.6+1.9 engine?what cause the compression to lower even more?
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Compression ratio is swept volume / un-swept volume. The rotating assembly determines the swept volume. The shape of the piston crown, the space between piston and head and the shape of the combustion face of the head determine the un-swept volume. Because there is a considerable volume to the combustion chamber in the head (un-swept volume), changing to a head from a larger displacement engine increases un-swept volume and lowers compression. Changing the rotating assembly to one from a smaller displacement engine lowers compression as well. Going to a 1.9 head and a 1.5 rotating assembly will result in the lowest compression using stock IDI parts. Because in stock form the pistons come darn close to hitting the valves already, your options for increasing compression are limited to decreasing the pre-chamber volume or increasing swept volume (goodbye 1.5 rotating assembly).
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1.5 compression ratio is 23.5:1
1.9 static compression ratio is 22:1 (someone confirm this for me, I am not 100% certain)
volume of 1.9 swept is 474053.67mm3
.: unswept is 21547.89mm3
volume of 1.5 swept is 367707.71mm3
.: compression ratio of a 1.5/6/9 engine would be something like 17.06:1
FWIW the difference in stroke between the 1.6 and 1.5 is actually 8mm, which is more like 5/16" :-)
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never thought that stroke would afect C.R.
if the piston would project the same as the 1.6 the C.R. would be the same or so i thought...
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Changes in stroke affect the swept volume and so directly affect compression ratio.
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1.5 compression ratio is 23.5:1
1.9 static compression ratio is 22:1 (someone confirm this for me, I am not 100% certain)
volume of 1.9 swept is 474053.67mm3
.: unswept is 21547.89mm3
volume of 1.5 swept is 367707.71mm3
.: compression ratio of a 1.5/6/9 engine would be something like 17.06:1
FWIW the difference in stroke between the 1.6 and 1.5 is actually 8mm, which is more like 5/16" :-)
I didn't look up the spec for actual displacement, but your math looks right. It's fun to see someone else crunch numbers.
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I never realized how easy the math actually was. So a 1.6 with 1.9 head would be 18.4:1 not quite the 19:1 that I have normally heard. And a 1.9 with 1.6 head would be 27.4:1. Wow!!!!! Hillfolk has that combo.
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what would be the lowest cr for a "normal" start up?here (portugal)is very rare to see 0ēCelcius ...
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From my mad scientist calculations at a cr of 17:1 should put u at around 376psi(25.6bar). Which would normally be an engine that's getting pretty tired, but I'd think it would start. Something I think can hurt with the lower cr in idi is that to some degree u need the compression to help create the swirl. The gm idi guys seem to like a cr of 18 or 19:1 I think they probably have it right since the gm idi is probably the swirl chamber engine that had had the most money dumped into it for developing performance parts
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When you add a 1.9 head to a 1.6 (or 1.5), the exit of the pre-chamber is in the wrong place which I imagine doesn't help with proper combustion either.
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Hi,
may BMW 524 TD (6 cylinder) has now a compression ratio of approximate 18:1 and it is a mess to start it below 5°C . I think part of it is also the hot camshaft i have installed, but mostly due to the lowered compression ratio, stock is also 22:1.
Best Regard
Alleslowbuged
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When you add a 1.9 head to a 1.6 (or 1.5), the exit of the pre-chamber is in the wrong place which I imagine doesn't help with proper combustion either.
but usually 1.6 with 1.9 head is a performance upgrade and show good numbers...
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When you add a 1.9 head to a 1.6 (or 1.5), the exit of the pre-chamber is in the wrong place which I imagine doesn't help with proper combustion either.
but usually 1.6 with 1.9 head is a performance upgrade and show good numbers...
that is my thought too, i think the real performance advantage of the 1.9 head is the compression drop allowing more advance and a safer increase in boost, the larger itnake valve doesn't hurt i'm sure. but for a performance car u plan to drive in the cold i would think a ported 1.6 head will be very adequate.
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I don't have the figures the machinist was telling me but the biggest deal is the bigger valves. 1mm is a huge difference for some reason in performance. He claims the D shaped ports are no better than the O shaped.
I think the precup volume is the best way to drop compression if you wanted to. The space between the piston and head should be almost nothing with the head gasket installed. When thousandths make a difference for the different HG, you know just stuffing the thickest one in isn't going to end up well. It would be interesting to see how much difference one could get with the same everything and just altering precup volume. It isn't worth it for these 30 year old cars, but it would have been nice for someone years ago to have a VW IDI fetish and a dyno with lots of time on their hands.
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I don't have the figures the machinist was telling me but the biggest deal is the bigger valves. 1mm is a huge difference for some reason in performance. He claims the D shaped ports are no better than the O shaped.
I think the precup volume is the best way to drop compression if you wanted to. The space between the piston and head should be almost nothing with the head gasket installed. When thousandths make a difference for the different HG, you know just stuffing the thickest one in isn't going to end up well. It would be interesting to see how much difference one could get with the same everything and just altering precup volume. It isn't worth it for these 30 year old cars, but it would have been nice for someone years ago to have a VW IDI fetish and a dyno with lots of time on their hands.
i think its because the amount of flow area u actually gain
1.9 has 36mm intake valves and 1.6 has 34 mm
so 1.9 has a flow area of 1018mm2 and 1.6 has 907mm2
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You forgot to take into account the valve stem.
If one has the newer 7mm valves in the 1.9 head you get flow a flow area of 979mm^2 and one a 1.6 with 8mm stems you get 857mm^2
That's 14% increase in flow area right there, also port design is better on the 1.9 heads.
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i went to the 1y engine because i was told that the valves had 7mm stems...
bad thing that of being hard or expensive to increase compression,i was tempted to do a weird franken engine,just because...
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You forgot to take into account the valve stem.
If one has the newer 7mm valves in the 1.9 head you get flow a flow area of 979mm^2 and one a 1.6 with 8mm stems you get 857mm^2
That's 14% increase in flow area right there, also port design is better on the 1.9 heads.
Right I had to just post quick and jump cause I was at work haha. But u showed what I mean, a tiny increase in valve size is a major increase in flow potential. I didn't really think of it like that till I ported my head and calculated the flow area just by opening the oval 1mm all the way around
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i went to the 1y engine because i was told that the valves had 7mm stems...
bad thing that of being hard or expensive to increase compression,i was tempted to do a weird franken engine,just because...
drop a 1.6 head on it if you want more compression..
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You forgot to take into account the valve stem.
If one has the newer 7mm valves in the 1.9 head you get flow a flow area of 979mm^2 and one a 1.6 with 8mm stems you get 857mm^2
That's 14% increase in flow area right there, also port design is better on the 1.9 heads.
Not kicking up dung, but from what my machinist says the D shaped port vs the hydro O port there is no gain. If anything he likes the O port better to start from. He has flowbench #s that support that and he had done 1.6 O port with bigger valves. Granted every head is cast a bit different, but the O port head he said will usually win if the valves are the same size. Again, from his data and the math done the real deal is in the valves.
I forget what this thread even started at???
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Flow benches can give you the answer you want it to give, It's just a matter of how you set up the test. It's not just the entrance shape of the port that is different. Does he flow test with the correct bore size and with the inlet manifold?
Off course your guy gets better numbers on O shaped ports, he is used to working on air cooled engines ;)
The valve spacing is different on the 1.6 vs 1.9 head so there is room for bigger valves in the 1.9 head, big advantage if going all out!
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Flow benches can give you the answer you want it to give, It's just a matter of how you set up the test. It's not just the entrance shape of the port that is different. Does he flow test with the correct bore size and with the inlet manifold?
Off course your guy gets better numbers on O shaped ports, he is used to working on air cooled engines ;)
The valve spacing is different on the 1.6 vs 1.9 head so there is room for bigger valves in the 1.9 head, big advantage if going all out!
I thought some of the advantage of the 1.9 head was the shape of the intake port its more of a straight shot to the valve the 1.6 is more curved looking. I just mean maybe that has more to do with it than d vs o, just speculation. I would think the d vs o is probably not much difference especially when ported 8v gassers are made to perform for sure. A local machine shop told when I was asking about bigger valves that u can actually buy off set valve guides and such to help with spacing which would help if using a 1.6 head and let te 1.9 go super mega large on valves haha
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Yeah, that is kind of what the machinist was saying trev. It isn't about bigger port, or straight shot, it is about velocity. If you speed up the air right as it enters the cylinder that is best. He seems to think the hydro 1.6 head has the best shape for that as cast and after porting.
....in other news, my head is being welded as we speak. I will post flow numbers when it is in my hands.
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Yeah, that is kind of what the machinist was saying trev. It isn't about bigger port, or straight shot, it is about velocity. If you speed up the air right as it enters the cylinder that is best. He seems to think the hydro 1.6 head has the best shape for that as cast and after porting.
....in other news, my head is being welded as we speak. I will post flow numbers when it is in my hands.
Your momma
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i went to the 1y engine because i was told that the valves had 7mm stems...
bad thing that of being hard or expensive to increase compression,i was tempted to do a weird franken engine,just because...
drop a 1.6 head on it if you want more compression..
that is a normal engine...
for start it must be 1.9 head,seems that best way is to stick with 1.6 bottom...
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So....any updates/experiments with chamber coatings yet?