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Pre combustion chamber design research

That is a path to follow, but consider this:
Why did the 6.2 become the 6.5? The fuel crunch was still in everyones mind, but power race had begun. It follows with all the gassers too, infact more so in gas cars.

Banks had a friend that owned a dealership and that is why and where he got involved in dealership up grades. Then the surrounding dealerships had to do it to compete. Everyone was willing to pay more a lot more for the added turbo power, because they were not allowed to advertise the improvement in mpg. Banks talked about all that in his interview.

Then factor in changes done for the military. They have no emissions standards. 1,920Brand new optimizers roll off the line every month and have since 2006. Not a single one passed federal emissions standards since 2004.

The diamond precups were a rework of the squares that was a change requested by the military to lessen visual smoke signature on take off in a convoy. They showed that 2 hmmwvs put up more cloud than the Abrams they were following, and 6 was the normal amount to follow.
When GM did the release, I rembember reading about the new precups and that they increase low rpm efficiency up to 2,000 rpm by only a couple percent but had same characteristics from 2,000-3,400 (the peak rpm for military engines). That part was on an update that went out to dealerships, if anyone here works at one maybe they can dig it up. We’ve all read about WarWagon’s 6.2 precups turbo smoke show, and he still cautions 6.2 owners about a big turbo from it. Similar issue of pouring on the fuel to get gowing with too low torque and 15,000lbs of weight.

Also recheck when you have diamonds coming out- they have been in a couple years before then, just maybe not into puckups. My 95 hummer that was n/a (so same block and heads as pickups not the van turbo) had diamonds in it that I reused into the heads on in my 6.5 Suburban.

Since the hummers were assembled at AM General plant, maybe all the diamonds all went to military first few years? Which since the military requested the new design, it sure wasn’t for nox. It is possible they lower nox as a byproduct of burning more efficiently on the lower half of the rpm band, idk.

A set of precups, headgaskets, and head bolts (unless arp already in place and a couple trips to the emissions tester is all thats need for comparisons to test the theory-
 
The 6.5 was definitely developed to feed the HP race. But they still had to meet the new emission standards put in place in 91. There is no way around that. So changes had to be made to make the power they wanted and still meet emission standards.

Thanks for the info about the diamond cups for the military! So did they use the square cups in the turbo engines before the diamond cups were developed? I always assumed they used the T cups. I could see 6.5 injectors and square cups causing alot of smoke on a hard take off. So if the diamonds were developed for smoke control it sounds like they have nothing to do with performance at all. The military is not concerned about emissions but I would think they do want good MPG and smoke control.

Testing emmision output is not a bad idea. I had plans to test different cup and injector combinations and thieir affect on HP. But seeing a change if any in emmisions is a good way to test my theory. Good thinking Will L.!!
 
I am not sure about T cups. I just remember the square to diamond change up, ad read about it at the chev dealership I worked at. Then later read the write up about it of the military pushing it.

And dont mix the less smoke/ efficiency thing. It does make more power at same fuel Amount because it is more efficient at the lower rpm half and same at upper.

Now how much that gets altered by outside factors likea big boy turbo instead of the toy one that comes on the engine is something else that has to be verified by you for your application. I tried them all with my hotrodded twin turbo set up, and diamonds wer the best of stock for power in my experience.
We tried cutting them open and never found anything that made big enough difference to bother with- but I was overloading the thing with fuel when we started adding the massive fuel.
 
Will L. said:
Also recheck when you have diamonds coming out- they have been in a couple years before then, just maybe not into puckups. My 95 hummer that was n/a (so same block and heads as pickups not the van turbo) had diamonds in it that I reused into the heads on in my 6.5 Suburban-
Click to expand...

This is interesting to me. My 2004 GEP 6.5 that came from an NA HMMWV didn’t have Diamond precups - it had Square cups in it. Did they change their thinking on this at some point?
 
Will L. said:
That is a path to follow, but consider this:
Why did the 6.2 become the 6.5? The fuel crunch was still in everyones mind, but power race had begun. It follows with all the gassers too, infact more so in gas cars.

Banks had a friend that owned a dealership and that is why and where he got involved in dealership up grades. Then the surrounding dealerships had to do it to compete. Everyone was willing to pay more a lot more for the added turbo power, because they were not allowed to advertise the improvement in mpg. Banks talked about all that in his interview.

Then factor in changes done for the military. They have no emissions standards. 1,920Brand new optimizers roll off the line every month and have since 2006. Not a single one passed federal emissions standards since 2004.

The diamond precups were a rework of the squares that was a change requested by the military to lessen visual smoke signature on take off in a convoy. They showed that 2 hmmwvs put up more cloud than the Abrams they were following, and 6 was the normal amount to follow.
When GM did the release, I rembember reading about the new precups and that they increase low rpm efficiency up to 2,000 rpm by only a couple percent but had same characteristics from 2,000-3,400 (the peak rpm for military engines). That part was on an update that went out to dealerships, if anyone here works at one maybe they can dig it up. We’ve all read about WarWagon’s 6.2 precups turbo smoke show, and he still cautions 6.2 owners about a big turbo from it. Similar issue of pouring on the fuel to get gowing with too low torque and 15,000lbs of weight.

Also recheck when you have diamonds coming out- they have been in a couple years before then, just maybe not into puckups. My 95 hummer that was n/a (so same block and heads as pickups not the van turbo) had diamonds in it that I reused into the heads on in my 6.5 Suburban.

Since the hummers were assembled at AM General plant, maybe all the diamonds all went to military first few years? Which since the military requested the new design, it sure wasn’t for nox. It is possible they lower nox as a byproduct of burning more efficiently on the lower half of the rpm band, idk.

A set of precups, headgaskets, and head bolts (unless arp already in place and a couple trips to the emissions tester is all thats need for comparisons to test the theory-
Click to expand...
Pickups didn't get diamonds until 97. My 95 heads came stock on mine and were squares. So it looks like the military got them first.
 
I spent some time digging through the M998 repair operator parts technical publication I downloaded. Alot of good specs in there for the 6.2/6.5, should come in handy on my rebuild.

Anyway both repair manuals I found are dated January 1996. I found no reference to T or Diamond cups in either one. In fact the only cup listed for the 6.5 is the 10230426 which Is the square cup. So it looks like the military used square cups in both the turbo and n/a 6.5 up until the diamond cup was introduced. Both would use the same injector just at different pop pressure I'd imagine.

It's interesting that the military didn't use the T cups. And if the diamonds were developed for smoke control it leads me to believe gm put T cups in to meet emission and the military ran square cups because they didn't have to.....
 
Well I've been looking everywhere for the bulletin Will L. Had talked about. I work at a independent shop so I only have so many resources. No luck yet but I did stumbled upon the updated version of the M998 technical publication. TM 9-2815+237-34p dated March 2001. I found this interesting.

The 6.5 n/a still calls for the 10230426 (square) cups. 96 6.5 turbo calls for 10149629 (circle) cups. And 97+ 6.5 turbo calls for 10183926 (diamond) cups. It did not mention pre 96 turbo so I assume it calls for the square cups? Also I found it weird the military called for circle cups in 96 only.

6.5 turbo injectors and n/a injectors did have different part numbers too. The 96 version only listed one. So maybe they only ran one style injector prior to 01.
Turbo- 10233973
N/a - 5743759 ( I could no cross reference this number)

More fun info I thought I'd share. If I ever find that bulletin I will post that too.
 
Rockabillyrat said:
Well I've been looking everywhere for the bulletin Will L. Had talked about. I work at a independent shop so I only have so many resources. No luck yet but I did stumbled upon the updated version of the M998 technical publication. TM 9-2815+237-34p dated March 2001. I found this interesting.

The 6.5 n/a still calls for the 10230426 (square) cups. 96 6.5 turbo calls for 10149629 (circle) cups. And 97+ 6.5 turbo calls for 10183926 (diamond) cups. It did not mention pre 96 turbo so I assume it calls for the square cups? Also I found it weird the military called for circle cups in 96 only.

6.5 turbo injectors and n/a injectors did have different part numbers too. The 96 version only listed one. So maybe they only ran one style injector prior to 01.
Turbo- 10233973
N/a - 5743759 ( I could no cross reference this number)

More fun info I thought I'd share. If I ever find that bulletin I will post that too.
Click to expand...


My '93 turbo ran a double square with a "T" cups.
 
Yes, my 04 GEP had the square precups in it also.
The 99 GMC Savanna had the diamonds.

Both are around 70,000 miles and both have cracks about the same length. They are all within spec to run, Not into fire ring, but shiney new ones in a “forever” engine would make me feel better.

I bother to mention the cracks because I remember there was some discussion regarding diamonds having less material and maybe being easier to crack, but they look at he same as the squares. I don’t believe diamonds crack any easier than any other precup.

I went threw and reread this thread and the 20 page one on tdp.

Has there been any new info on precup comparisons?
 
The diamond cups are getting really hard to find. I got a oversized set from Leroy. But he only had a few left and that was last year. Sometimes they pop up on Ebay. I know GEP wont sell them separately and GM discontinued them. I'm keeping them just in case I need them.

I've been continuously researching the cups. Just haven't been on the forum too much lately. I recently found a 300pg article on the thermodynamics of and IDI engine. And again it confirmed my theory on smaller cups are better for performance. They compared throat size, shape , and angle. And when compared to our style cups. The square comes up as the best match.

But just throwing small cups in an engine and calling it good is not going to work. It takes a combination of the right cups, a course spray patter with the correct flow rate curve. The swirl dishes machined into the piston are just as important. A IDI is a mechanical version of modern pilot injection found on a CR. It needs to be treated as such to get more power out of it.
 
Is there a list of part numbers to cups?
That would be some good info to add here.

I also started wondering about putting a tig to the fine cracks starting. Obviously would have to hand file back to proper afterwards. Just wonder if anyone has done it.

Something else:
It seems to me cracking in precups is sped up by higher egt. Maybe everyone else noticed it, but figured worth mentioning.
 
I believe I have most of the cup part numbers written down at home. I can post them for you later.

I've never attempted to tig weld a cup. The material it's made of might make it difficult. But all I play with is stainless on the tig so I have no experience to go off of.

High EGTs I would think aid in the development of cracks In the cup. So would boost, compression, and the throat diameter. The bigger the pressure differential at the cup the more heat it should make.
 
Yeah, the numbers would be great. Maybe get military nsn numbers from that. Which could tell us which is available from that avenue.

Square .010 over is 10230425
 
Rockabillyrat said:
A IDI is a mechanical version of modern pilot injection found on a CR. It needs to be treated as such to get more power out of it.
Click to expand...
What do you mean by this? Pilot injection is where you inject a small amount of fuel into the cylinder before the main injection pulse. Its injected normally in too small of a quantity to cause a combistion event, and injected before cylinder pressures have risen enough for there to be enough heat to ignite it. It works by putting fuel into the cylinder before the power syroke so you get a combistion event across more of the cylinder instead of just at the injector tip. This is how it reduces engine noise and emissions. I know they have accomplished this on mechanically injected diesels by putting grooves in the pump nozzles, but I don't see how this applies to a precup or idi specifically.
 
Here are the numbers I have for the 6.5 precups.

Square -10230426
Circle - 10149629
T - 10149630
Diamond - 10183926

GEP Diamond Over sized - 12550985

THEFERMANATOR said:
What do you mean by this? Pilot injection is where you inject a small amount of fuel into the cylinder before the main injection pulse. Its injected normally in too small of a quantity to cause a combistion event, and injected before cylinder pressures have risen enough for there to be enough heat to ignite it. It works by putting fuel into the cylinder before the power syroke so you get a combistion event across more of the cylinder instead of just at the injector tip. This is how it reduces engine noise and emissions. I know they have accomplished this on mechanically injected diesels by putting grooves in the pump nozzles, but I don't see how this applies to a precup or idi specifically.
Click to expand...

A IDI has a very short delay period so timing is generally less than a DI engine. The delay nozzle in the injector limits the amount of fuel entering the swirl chamber at initial pintle lift. That small amount of initial fuel is pushed to the outer edge of the chamber. Where it starts the combustion process due to the heat from the chamber walls. As the pintle lifts, more fuel is pushed into the chamber. The piston reaches TDC and most of the air is consumed in the chamber leaving a very rich mixture. This is what I refer to as the pilot part of the combustion process. A common rail has the advantage of being able to fire 5 separate times in a combustion event. We can't do that with an IDI so this is as good as it gets.

The chamber reverses flow and searches for air in the main chamber. The cup throat creates a pressure differential that atomizes the remaining fuel still being injected for combustion in the main chamber. The flame front hits the swirl dishes on the pistons finishing the combustion event. This is what I call the main event.

I view the precup as part of the fuel injection process since its responsible for the atomization of fuel into the main chamber. It's a two step process and in some ways mimics what they are doing with common rails. Its Its obviously limited but I think when you look at the thermodynamics of it they have similarities.
 
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