Power Ceiling At 160Rwkw - Restricted Flow?

[clip14]

91 r32 just came off the dyno

rb25det

t3/t04e

supporting fueling modifications

we are hitting a ceiling at 160rwkw at 5psi. ran up to 12psi and pulled all timing back and no change in power output

engine sounds fine on the headphones, air fuel ratios are safe, we have fuel for more power even at base pressure. turbo responds like a mid sized t3/t4 hybrid - positive pressure around 3000rpm, no weird noises

took a pressure reading from after the turbo, and also at the manifold - exactly the same power curve so we don't think it is a restriction in the intake/intercooler piping

airflow meter (z32) output voltage ramps up quickly with boost and then holds static voltage from there (with increasing rpm and boost).

the exhaust came with the car - I am thinking a collapsed muffler (baffles) or something??? it is 3.5" all the way through with one resonator and a rear super dragger muffler, but it is quite quiet

has anyone else run into similar issues before? could it be any other part of my system?

[R31Nismoid]

Given it's a 10min job to drop the exhaust and do a run, surprised you didn't to rule it out as an issue if you went to the effort of testing the pressure.

BUT... you tested the pressure, so you would know if it was a problem or not... So what were the results of that test? Was it overtly pressurised?

Either that or cam timing/belt is out a tooth. Seems fairly common that one.

[clip14]

while the problem was being diagnosed, the turbo oil feed line had a minor split and so we shut it down - didn't want to pull any power runs until we sorted that out since a major failure on the pressure side of the oil system would mean dead engine real quick.

we only took pressure values from the intake side, from the nipple right after the turbo compressor housing, and again at the inlet manifold. pressure readings were the same at both locations

I'm getting the oil line sorted shortly and just wanted to hear any opinions before I started down the road of figuring out this problem

we pulled the timing right back while trying to diagnose on the dyno with no change to the power output - surely if the belt was off we would have seen some changes there?

Edited October 1, 2012 by clip14

[R31Nismoid]

took a pressure reading from after the turbo, and also at the manifold

I'm now confused given you said the above.

What post turbo pressure reading did you take?

[clip14]

sorry for the confusion, i meant inlet manifold - only took pressure readings on the intake side

post turbo pressure held 12psi, inlet manifold pressure held 12psi as well. no power change from 5 to 12psi.

[Super Drager]

I'm betting your cat is a std compliance cat and/or royally fkd.

[GTSBoy]

Stable AFM voltage with more boost and revs certainly does indicate that you are maxing out the flow capability of something. And the exhaust/cat is the #1 place to look.

[clip14]

Cat has been removed - exhaust set up is as follows

factory exhaust manifold

38mm gate taken off the manifold before the turbo

custom downpipe with external gate plumbed back in

no cat

3.5" exhaust with one resonator and one rear muffler (installed prior to purchasing car).

[GotsWapan]

My rear super dragger muffler was all rusted and colapsed on the inside. They're a fairly old muffler I think. Ended up gutting it.

[Super Drager]

Could be Timing is out a tooth.

[t_revz]

we pulled the timing right back while trying to diagnose on the dyno with no change to the power output - surely if the belt was off we would have seen some changes there?

Belt is for cam timing. You were adjusting ignition timing

[R31Nismoid]

Cat has been removed - exhaust set up is as follows

factory exhaust manifold

38mm gate taken off the manifold before the turbo

custom downpipe with external gate plumbed back in

no cat

3.5" exhaust with one resonator and one rear muffler (installed prior to purchasing car).

I'd still be dropping the exhaust and doing a run/two to rule it out.

Very common for Jap exhausts to have 2.5" restrictors welded in before/after resonators/mufflers etc.

[STATUS]

165 is also around the max a faulty cas makes, did the curve go wavy? look at exhaust first.

[clip14]

My rear super dragger muffler was all rusted and colapsed on the inside. They're a fairly old muffler I think. Ended up gutting it.

the muffler is not in great condition - will replace it this weekend. cheers

Belt is for cam timing. You were adjusting ignition timing

right, sorry about that. i had a chat with my tuner, he says he played around with the vct and it didnt look like there was a problem there. He will check the cam timing before it goes back onto the dyno.

I'd still be dropping the exhaust and doing a run/two to rule it out.

Very common for Jap exhausts to have 2.5" restrictors welded in before/after resonators/mufflers etc.

will be dropping the entire exhaust and making sure it is alright - most likely will just get a new rear section rebuilt to be sure.

165 is also around the max a faulty cas makes, did the curve go wavy? look at exhaust first.

I dont have the output from the previous dyno runs on hand. what do you mean by wavy? which curve?

Is there any other way to troubleshoot a faulty CAS?

Thanks everyone for their responses!!

Edited October 4, 2012 by clip14

[GTScotT]

I dont have the output from the previous dyno runs on hand. what do you mean by wavy? which curve?

Is there any other way to troubleshoot a faulty CAS?

Meaning as it was on the dyno was the readout on the screen wavy? Going up and down as power rose. Or was it a smooth steady line?