Author Topic: IDI engine, there IS a future...  (Read 83176 times)

Reply #15October 29, 2005, 06:13:12 pm

gratefuljoe

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much props
« Reply #15 on: October 29, 2005, 06:13:12 pm »
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))

Reply #16October 29, 2005, 06:14:58 pm

RedRotors

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« Reply #16 on: October 29, 2005, 06:14:58 pm »
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.. :)






I took some closeup of the crack for you Bruce.

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 #17October 29, 2005, 07:37:14 pm

QuickTD

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« Reply #17 on: October 29, 2005, 07:37:14 pm »
Quote
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...

Reply #18October 29, 2005, 08:39:28 pm

RedRotors

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« Reply #18 on: October 29, 2005, 08:39:28 pm »
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.



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..




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

-> www.mikrotuning.com <-
-> www.hflox.com <-

Reply #19October 30, 2005, 09:40:42 am

QuickTD

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« Reply #19 on: October 30, 2005, 09:40:42 am »
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,


Reply #20October 30, 2005, 12:11:23 pm

VWRacer

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« Reply #20 on: October 30, 2005, 12:11:23 pm »
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.
Stan
C-Sports Racer

Reply #21October 30, 2005, 01:34:46 pm

RedRotors

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« Reply #21 on: October 30, 2005, 01:34:46 pm »
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/
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

-> www.mikrotuning.com <-
-> www.hflox.com <-

Reply #22October 30, 2005, 09:58:31 pm

jtanguay

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« Reply #22 on: October 30, 2005, 09:58:31 pm »
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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Reply #23October 31, 2005, 09:39:36 am

greggearhead

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« Reply #23 on: October 31, 2005, 09:39:36 am »
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.
Caddy (TD Project), Caddy 1.6D, etc etc.

  Snow Performance Water-Methanol Injection

Reply #24October 31, 2005, 10:09:42 am

jtanguay

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« Reply #24 on: October 31, 2005, 10:09:42 am »
well the constant abuse the fabric would take will ultimately destroy it eventually, but how long is the question...


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Reply #25October 31, 2005, 01:04:28 pm

fspGTD

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« Reply #25 on: October 31, 2005, 01:04:28 pm »
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.
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #26October 31, 2005, 04:44:09 pm

RedRotors

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« Reply #26 on: October 31, 2005, 04:44:09 pm »
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/
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

-> www.mikrotuning.com <-
-> www.hflox.com <-

Reply #27October 31, 2005, 05:01:10 pm

QuickTD

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« Reply #27 on: October 31, 2005, 05:01:10 pm »
Quote
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...

Reply #28October 31, 2005, 05:53:33 pm

fspGTD

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« Reply #28 on: October 31, 2005, 05:53:33 pm »
I found some data from believe it or not, Greg Raven's book "Water cooled Performance VW handbook".  P .32
Quote
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:
Jake Russell
'81 VW Rabbit GTD Autocrosser 1.6lTD, SCCA FSP Class
Dieselicious Turbocharger Upgrade/Rebuild Kits

Reply #29October 31, 2005, 06:42:46 pm

Mark(The Miser)UK

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« Reply #29 on: October 31, 2005, 06:42:46 pm »
Quote from: "QuickTD"
Quote
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)
Mark-The-Miser-UK

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