Att dyno results

[buddy]

So what you're saying is- with higher fuel rates, and better turbo, it don't matter what precup is used?

6.2turbo noted more turbo lag, and more smoke with his larger (t ?) precups.

And just for clarification, 6.2turbo is using STANDARD 16cm turbo housing. Keep your facts strait buddy.

My apologies, I forgot he uses the 50, not the 52. Its a small housing compared to available 19, 22 and 17 seemed popular, nearly impossible to find all the specs available for a Holset. HX40s can come with larger housings than that.

It does matter for efficiency of the burn, dont want to be wasting fuel, unnecessarily heating things up, or getting unbalanced combustion. There are several reasons his setup might have felt slower than a previous build. Sometimes its hard to repeat the secret sauce with a tweaked IP or engine setup. His IP was giving him issues. When he has one running good, free of issues, I'm sure he will figure it out. He has an experimental type setup, you cannot always relate to what everyone else has.

 

[buddy]

Thats the thing about seat of the pants. Its not consistent, and its not factual. Not to try and discount what Hank said, but without a real back to back dyno its impossible to know truthfully the differences.

But when you couple it with 5 years of other information, how trucks run, and other projects, its been a relatively common them that the larger cups run better power. This is not an isolated case.

 

[nmb2]

But when you couple it with 5 years of other information, how trucks run, and other projects, its been a relatively common them that the larger cups run better power. This is not an isolated case.

I understand this, but 5yrs of information doesn't change the physics of how our IDIs work. In our IDI's, the cups are pre-combustion chambers.

Injection occurs near the top of the compression stroke, only part of the fuel is burnt in the pre-combustion chamber because of the limited amount of air inside. The high rise in pressure forces the atomized/burning fuel into the main combustion chamber to finish.... It is this "secondary" explosion that you get your power from.

So, a bigger pre-cup, not talking about the mouth... the mouth is of almost no relevance... I am talking about the cups physical volume...... a bigger pre-cup, will lower emissions, but also lower bottom end power.

Now, its not all cut and dry... black and white. There is other variables. Your turbocharger, your fuel system, your camshaft, your turbo kit, your injection timing... plenty of other variables. I'm just letting you know how an IDI works. No matter what changes, the way an IDI works does not change.

Your engines obviously take to modifications differently than mine, but the general idea is the same.

So the questions I have so that I might be able to further understand or help out is this.

What is the accepted "norm" for good power. RWHP/RWTQ @ what rpms.... real dyno numbers, not guesses.

What fuel output does it take to achieve this?

What is the volume of the pre-cups.

 

[6.2 turbo]

I cc'd them ,but forget what it was. The cup itself has very little volume,but combined with the chamber in the head might be 20cc's.

 

[buddy]

I understand this, but 5yrs of information doesn't change the physics of how our IDIs work. In our IDI's, the cups are pre-combustion chambers.

Injection occurs near the top of the compression stroke, only part of the fuel is burnt in the pre-combustion chamber because of the limited amount of air inside. The high rise in pressure forces the atomized/burning fuel into the main combustion chamber to finish.... It is this "secondary" explosion that you get your power from.

So, a bigger pre-cup, not talking about the mouth... the mouth is of almost no relevance... I am talking about the cups physical volume...... a bigger pre-cup, will lower emissions, but also lower bottom end power.

Now, its not all cut and dry... black and white. There is other variables. Your turbocharger, your fuel system, your camshaft, your turbo kit, your injection timing... plenty of other variables. I'm just letting you know how an IDI works. No matter what changes, the way an IDI works does not change.

Your engines obviously take to modifications differently than mine, but the general idea is the same.

So the questions I have so that I might be able to further understand or help out is this.

What is the accepted "norm" for good power. RWHP/RWTQ @ what rpms.... real dyno numbers, not guesses.

What fuel output does it take to achieve this?

What is the volume of the pre-cups.

You dont have to come and teach us how stuff works. I am talking about mouth sizes, not volume. I would beg to differ that that the opening is of no relevance. Larger internal volume reduces the compression ratio of the engine. This is how GM reduced CR from about 21.3 to 20.2:1. You might consider a lower CR for emissions only, but I dont. It does produce less cylinder heat for lower NOX perhaps, but GM was having a hell of time keeping them from blowing heads, cranks and blocks after putting the turbo on. The turbo is a factor for reducing CR, since it increases cylinder pressure as well.

I am talking about mouth opening, for the speed with which the flame can exit the cup, and it having a good relevance.

 

[nmb2]

I cc'd them ,but forget what it was. The cup itself has very little volume,but combined with the chamber in the head might be 20cc's.

That's very small.

You dont have to come and teach us how stuff works. I am talking about mouth sizes, not volume. I would beg to differ that that the opening is of no relevance. Larger internal volume reduces the compression ratio of the engine. This is how GM reduced CR from about 21.3 to 20.2:1. You might consider a lower CR for emissions only, but I dont. It does produce less cylinder heat for lower NOX perhaps, but GM was having a hell of time keeping them from blowing heads, cranks and blocks after putting the turbo on. The turbo is a factor for reducing CR, since it increases cylinder pressure as well.

I am talking about mouth opening, for the speed with which the flame can exit the cup, and it having a good relevance.

sounds like you may just be plagued by a poor mix of parts. I thought us IH guys had it rough.

I would still love to know the pre-cup volumes just for comparisons sake, as well as your standard power outputs, with what amount of fuel.

I keep looking around and see some of these 260/400. Is that with the DB2? .29 or .31?

 

[nmb2]

these are our 3 cups:

left is the 7.3 - 21.5:1CR , middle is the 84+ 6.9 22.5:1CR , right is the early 83 6.9 20.7:1CR

the 7.3 cup is 20.42cc's, the middle 6.9 cup is 18.34cc's, and I've never had my hands on the far right. Highest powered IDI's are running the middle cup.

 

[buddy]

Stock rating was 190hp and 430ftlbs at the flywheel. That was with 65mm^3 of fueling, 9psi of boost stock for the later DS4 electronic injection engines. We dont have a lot of dyno runs, because 6.5 owners dont make really impressive numbers to brag so much about and are usually strapped for cash. The typical power program from the aftermarket pushed about 80mm^3 of fuel. You can get more than that with some tweaking of the program, but thats what most people are working with, probably similar to a turned up DB2 IP.

Our CR is over 20:1, so the squish space (gasket thickness ~0.04") plus the precup is a small volume, the 6.2s having the smallest inner volume cups, and the mouth opening removes more of the cup as well. I can do the math, but I have it at home compared to the displacement and clearance between piston and head what the precup volume is.

 

[Slim Shady]

I am wondering if the pre cups between our engines are close to being interchanged with no to little modification. Can we share some measurements. The center pre cups look like what I was running before modifying mine. They ran good and gave me good towing power. The large modified pre cups work well in low rpm and high rpm but the middle ground lacks any real power. Getting ready to change them out soon and go back to another pre cup set up. I will try and get a dyno run in before that and one after to document the changes.

 

[buddy]

From my calculations, the internal volume of the precup to get a CR of 20.2:1 in later 6.5 must be ~30cc, the stock 21.3:1 CR would need a precup volume of ~27cc. These volumes include the volume of the opening. Any material removed from the precup lowers the CR. In a 6.2, with 21.5:1 CR the precup would have been ~25cc.

Thats assuming a piston that sticks out of the deck about .005" and gasket thickness of .045" for that .04" between piston and head (8.5cc), and then estimating the amount of volume in the ricardo swirl bowls and flame guide (which accounts for about 3cc).


The openings into the cylinder increased with each iteration of the engine that increased fueling and rated power. The internal volume also increased over time, most so in the highest power non-emission engines with turbo. I spoke to Peninsular Diesel a while back and they suggested maybe there was a military or marine precup that had a larger opening than the diamonds, for their turbo diesels. But he didnt have pictures or references for them. It looks like the highest power civilian 6.5 was rated at 195hp, at the flywheel, in recent years I believe new improved castings of military blocks used more fueling and ran it over 200hp.

 

[Slim Shady]

If I get time today I will stop by Peninsular Diesel, I go by there at least a few times a month and have never stopped in there. I do however go to the shop that does their diesel injector and pump work. Had a very interesting discussion with shop foreman. I will be talking with the owner today if he and I can get some time where neither one of us is busy.