RajDatta

That should be an easy test at the dyno. Run the car with the downpipe and exhaust and then remove it. See what happens. I don't want to cut into this system, its too rare, unless ofcourse it is clogged up and restricting airflow.

Also, a restrictive Cat would glow orange when the car is running. This would be easy to see on the dyno.

Paulyy

things like the cat are made to be replaced. Im not to familier with US spec cars because the euros and most Aus cars where made to run leaded fuel so had no cat, just a resonator. But it should be the same cat as a 951?

RajDatta

The cat is much bigger. It looks like it is a higher flow unit. The diameter is bigger and it is shorter than a 951 cat. I just added a picture of the factory unit side by side with my setup.

Also, even though the 968 turbo S was designed to be able to be sold in US, it was never sold in US. It was a ROW car only. Selling it in US was under consideration but it never equated into any sales.

Paulyy

It probably is a higher flowing unit.
The only issue running on a dyno with no exhaust is that the restriction of the 2.5" is missing so the results would be invalid unless you can hook up a standard 951 exhaust and delete the cat.

RajDatta

I would think the cat would start getting very hot if its clogged up. Also, we could do pre-cat and post-cat temp comparisons to see if there are restrictions.

If that is the cause of my issues, I will have to either swap the cat or have another one built to match this design.
The good part is, fabspeed is local to me. I would think they would also be able to test my setup for flow.

Another idea would be to have a good 951 cat setup available to slap on to test.

Paulyy

If you can rule that out, Then you'll need to look somewhere else. The dyno seems like the turbo is chocking. but if that isn't a WOT run, you can't use it as a reference.

Before you test the exhaust, go get a WOT run on a dyno. log boost & afrs also.
Do a run with the airbox out for comparison. It might help spool better. Not saying if it helps to remove it, but it just will show you if there's an intake restriction which causes lag and loss of power.

RajDatta

Paully, you have great suggestions and I will definitely try those out.

86 951 Driver

Were those turbo you are using used on the real Turbo 968?

Paulyy

No, the original turbo is a k27 series turbo. Pretty sure it's a k27/8

Dave W.

Twin 2" pipes have the same flow area as a single 2.8" pipe which is plenty for 400hp unless there's a bottleneck somewhere along the way.

NZ951

I would think you would want to be measuring pressure differentials as well, pre and post turbo and cat and IC for example etc...

Thom

The S is a K26/?, while the RS is a K27/11.

Raj, I apologise if this is not what you want to hear, but I think you are chasing your tail. You want the car to be as original as possible but you won't replace a GT30, that will never work as it should with such a restricted exhaust, with a stock K27? I don't get it...

Paulyy

Thanks for the correction, i read somewhere it was a k27 series turbo in the S. ah well they may be wrong.

NZ951

K26/8 in the S I believe.

reno808

944 Turbo S runs a k26/8