T3 footprint/Port size and S366/74/.91...Restriction Questions...

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RacinNdrummin

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I have been beating my head over this one for awhile, and I have been chalking it up to a restriction pre-turbo on my previous setup.

Does anybody have any issues with exhaust manifold restriction on an S366 causing a low boost issue?

Both banks of my exhaust ran through a 2.100" (~3.5 sq.in) opening before heading up to my .91 housed S366. I was wondering if Pre-turbine housing back pressure could have been affecting my drive pressure at the turbine, and therefore causing a low boost situation. A divided T3 footprint is roughly the same area, so I was wondering if anybody else has seen similar issues with a T3 manifold limiting peak boost with an S366 setup?

I have a new setup going in now, so its no longer an issue, or shouldn't be, but its just something I haven't really been able to pinpoint in my setup, and Im curious to see if its a common issue on other platforms...

For those curious, my setup is a 6.9IDI, 195cc of fuel (180 at torque peak), Cammed, S366, intercooled, 18:1, 910's shimmed .030", smith bro's pushrods. I was seeing 32psi at peak with the restrictive (2.100" stuff) while a fellow IDI'r with a similar setup is seeing around 37psi with an Aurora 3000 on a 7.3 with the same cam, and even on my old custom hotside on my old 7.3, same cam, with a lesser pump, I was seeing 34psi with an S362/65/14wg....

Any ideas other than junk the IDI, bro?? Again, this isn't a current issue, the setup is being changed right now, but im just curious...
 
If the t3 was the restriction how would a cummins make 60psi out of the same charger? Unless I'm understanding it wrong?
 
That's what I am asking, is this something cummins guys run into when just running a T3/T4 adapter.... Obviously it wouldn't be an issue on a T4 footprint manifold...

Also, fuel and displacement are a big issue... I know the 7.3psd guys generally see high 30's low 40's for boost with the same charger and similar fuel... However, the question was mainly looking at the sizing as a constant...

Is there an increase in Turbo effectiveness when going from the stock manifold to a T4 manifold on a cummins? Im not talking spool time or anything like that, but higher boost numbers caused by more work acting on the turbine wheel...
 
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you may just not have enough ass to spool the charger. Or a boost leak.
 
The divided T3 housing is smaller, therefore driving the turbine harder on the old turbo. The drop in boost Seems normal to me if you can't drive the larger housing/ turbine hard enough
 
Comparing the boost from a 6cyl with a restrictive head to a larger cubic inch 8 cyl will change things I'm sure. More room for the boost pressure to go.
 
I run a t3-t4 adapter with a t4 66-74-.91 and see 60 psi all day ury day with moderate fuel at best.
 
I have a question along the same lines....

would it be defeating the purpose of having a ported head by restricting it into a T3 housing ?
 
Hurley said:
you may just not have enough ass to spool the charger. Or a boost leak.
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No Obvious Boost leaks, The IC has a very tiny pin hole in one of the factory welds, but its not going to bleed off that much volume. I was running this IC on the last setup too.

As far as Ass to spool the turbo, that's possible as far as tuning is concerned, I never got it on the dyno to tune it with that setup. These pumps have a very convoluted dynamic timing setup, and when my new setup goes back together, im going to lock it out to avoid problems. Realistically, that's the only thing that separates these from a 7.3psd is the ability to 2d map the timing. Airflow is the same if not a bit better than a psd...

Im not completely ruling out a gauge issue as well, I was running autometers, so it could be off, but it didn't quite feel like it had the ass it should.

I guess well see when my new turbo kit goes on, I am also doing an HX35 over the 366, so any spool issues should be non-existent.
 
mathews8pt said:
The divided T3 housing is smaller, therefore driving the turbine harder on the old turbo. The drop in boost Seems normal to me if you can't drive the larger housing/ turbine hard enough
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Smaller all around turbo, 65mm exhaust wheel vs. a 74mm exhaust wheel, but the last hot side I was running was a total custom setup with a nominal inner diameter of 1.61 (Schd40 1.5" pipe) per bank which is 4.07sq.in of area, so even it out flowed stock style setup, and the turbine was the smallest point in the system.

New setup has 1.75" nominal ID per bank, and shorter up pipes, so at least it will be comparable to the PSD setup, and I know that guys can spool a 366 on stock sticks, which is less fuel than I have... So well see.
 
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zfaylor said:
I just noticed this is on a 6.9.... holy chit. :Cheer:
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Yeah, Its about as full tilt as you can build a 6.9, with the exception of the stuff im about to do to it... Its getting H13 studs, Orings, EDM'd nozzles, 7.3 pre-cups and a new cam to go with the compounds and new turbo kit... Shooting for numbers in the 400-500 at the wheels range if she doesn't want to be a little biotch about it... I should have done it this way from the beginning but I had the goal to do it with a stock style setup, that was a bad choice, so I am doing like I should have now.
 
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triton said:
would it be defeating the purpose of having a ported head by restricting it into a T3 housing ?
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I would go T4, get the heat out out of the cylinders, and let it breathe better, especially on the top end.
 
chevota84 said:
Have you checked drive pressure?

Sent from my SCH-I545 using Tapatalk
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On that setup, no... The first real run out with the 366 I popped a HG do to a concoction of crap, part of which is the point of this thread. I was trying to see if my low boost issue was also an issue of back pressure before the restriction, causing the number 2 cylinder (the Hottest cylinder) to pop. I know timing was out of wack due to heavy referenced pump inlet pressure (37psi on a pump benched for 6psi inlet pressure) and that is why I am going to be locking the timing out, but you also couple that with high back pressure because of a restriction pre-turbo, timing, high injector pop-pressure, and poor airflow to the #2 cylinder and it was just not a good situation, lol.

Along with fixing the issues above, I am getting a full set of Isspro's including a DP gauge.
 
That is the stanadyne rating for inlet pressure on these pumps, and that's where I had my pump benched at just for comparison to the "lesser" pumps... It puts out a bit more fuel with more inlet, not more peak, but the curve comes up some. I am going to have the pump benched with 20psi inlet (Ill regulate my reference to see that peak, just to be easy on the pump, these things sound terrible above that, its scary on the stand), locked timing, and a HPCA (cold advance) delete which basically drops all housing pressure to provide a better differential for plunger filling, that's good for about 10cc's. Also going to try some new accumulators. The metering valve is a restriction, at least at the level im at, so its hard to get the curve up, but that has been my main goal with the pump, Im trying to have as flat of a curve as possible, while keeping the pump alive. As it is, it already bogs the DB pump stand down above 3300 engine RPM, I cant get an accurate reading above that. It would be nice to get a full 190+cc curve to 4K, that would for sure get me to my goals.
 
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