Author Topic: IDI engine, there IS a future...  (Read 78790 times)

October 28, 2005, 01:37:55 pm

RedRotors

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IDI engine, there IS a future...
« on: October 28, 2005, 01:37:55 pm »
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/


2k1 Golf TDI, 11mm pump, HFLOX Warp 5, VNT17, Wavetrac, 4" Lift
91' VW Golf Country
94' Dodge RAM 2500, 4x4, Cummins, 5 spds, 191's, 215hp injectors, SB Clutch
03' Dodge RAM 2500, 4x4, Cummins, 6 spds, MBPR 4 ", custom intake, Smarty Jr

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Reply #1October 28, 2005, 03:09:23 pm

fspGTD

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« Reply #1 on: October 28, 2005, 03:09:23 pm »
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!
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #2October 28, 2005, 03:44:09 pm

lord_verminaard

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« Reply #2 on: October 28, 2005, 03:44:09 pm »
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
81 Scirocco 'S -->Soon to be m-TDI
93 Corrado SLC VR6
'86 Golf N/A Diesel  -->Wife's car
1990 Audi CQ
05 New Beetle PD TDI


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Reply #3October 28, 2005, 04:27:54 pm

moTthediesel

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« Reply #3 on: October 28, 2005, 04:27:54 pm »
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
'82 LandCruiser Diesel Conversion
4Cylinder 3B/KKKturbo/AudiIntercooler(gone, BNF)
'92 Dodge/Cummins D350 Getrag Dually
356 w/Quantum 1.6TD (73 mpg!)
'85 BMW 524td (Der Komisar) 
'00 Jetta TDI 5spd

Reply #4October 28, 2005, 06:03:16 pm

RabbitGTDguy

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IDI engine, there IS a future...
« Reply #4 on: October 28, 2005, 06:03:16 pm »
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
1979 Rabbit mTDI crazy $*(\%& bunny...
1972 VW Westfalia
2009 VW Tiguan SE 2.0T (Wife's car)
2001 Audi TT 225 Quattro Roadster (something newer :) )

Reply #5October 28, 2005, 07:18:02 pm

msrochester

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« Reply #5 on: October 28, 2005, 07:18:02 pm »
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

Reply #6October 29, 2005, 12:01:23 pm

VWRacer

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« Reply #6 on: October 29, 2005, 12:01:23 pm »
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:
Stan
C-Sports Racer

Reply #7October 29, 2005, 12:31:26 pm

fspGTD

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« Reply #7 on: October 29, 2005, 12:31:26 pm »
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.
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #8October 29, 2005, 01:11:12 pm

VWRacer

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« Reply #8 on: October 29, 2005, 01:11:12 pm »
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?
Stan
C-Sports Racer

Reply #9October 29, 2005, 02:16:59 pm

fspGTD

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« Reply #9 on: October 29, 2005, 02:16:59 pm »
Quote from: "VWRacer"
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.
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #10October 29, 2005, 02:29:02 pm

VWRacer

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« Reply #10 on: October 29, 2005, 02:29:02 pm »
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:
Stan
C-Sports Racer

Reply #11October 29, 2005, 02:51:05 pm

fspGTD

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« Reply #11 on: October 29, 2005, 02:51:05 pm »
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.
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #12October 29, 2005, 03:31:36 pm

VWRacer

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« Reply #12 on: October 29, 2005, 03:31:36 pm »
Got it...thanks Jake!  :D
Stan
C-Sports Racer

Reply #13October 29, 2005, 04:11:45 pm

RedRotors

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« Reply #13 on: October 29, 2005, 04:11:45 pm »
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..







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:









I hope to keep this subject 'hot' with comments and experimentation results from everyone..

Cheers,
Marc/
2k1 Golf TDI, 11mm pump, HFLOX Warp 5, VNT17, Wavetrac, 4" Lift
91' VW Golf Country
94' Dodge RAM 2500, 4x4, Cummins, 5 spds, 191's, 215hp injectors, SB Clutch
03' Dodge RAM 2500, 4x4, Cummins, 6 spds, MBPR 4 ", custom intake, Smarty Jr

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Reply #14October 29, 2005, 05:41:19 pm

QuickTD

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« Reply #14 on: October 29, 2005, 05:41:19 pm »
Quote
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... :)