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Pre combustion chamber design research

Will L.

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#41
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-
 

Rockabillyrat

Active Member
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Location
Ohio
Thread starter #42
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.!!
 

Will L.

Well-Known Member
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Location
Boulder City Nv
#43
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.
 

n8in8or

Well-Known Member
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2,925
Location
Kalamazoo, MI
#44
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-
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?
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
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Location
ZEPHYRHILLS FL
Staff #46
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-
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.
 

Rockabillyrat

Active Member
Messages
42
Likes
102
Location
Ohio
Thread starter #47
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.....
 

Rockabillyrat

Active Member
Messages
42
Likes
102
Location
Ohio
Thread starter #48
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.
 
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