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321rwhp @20psi. 4psi more boost has got me 30hp less than my previous tune.

No symptoms this time. Tuner double checked my cam timing, said I got it spot on. He even tried playing with the exhaust cam gear, but best results were where I had it. Set base ignition timing before it went on the dyno. IAT's are fine, not getting hot. It had no problems taking boost, it wasn't misfiring, it had plenty of fuel. It just doesn't make power. And I'm stumped.

Wow man that's no good. Don't worry though man, if the engine's healthy (certainly sounds like it is) then it's just a matter of time until you find the cause.

Keep methodically checking through the possible causes and you'll nail it eventually.

Hopefully not but, are you sure the turbo is ok?

What do the graphs look like?

Mabye the turbo is a dud?

You might need to swap turbo out for a "spare"

See what another turbo does
That way you can rule that out?

Edited by jay-rod

I don't really think there should be much issues on the design of the turbocharger since every one's made 320hp+ on fair basic mods on stock cams. I'll be happy to check and update it to the most recent profile if Halando is happy to send it.

T04Z I've engineered the comp wheels in couple of different sizes and blade shaps. I like to see what they can do on the GT35 based turbine wheel first. The T04Z turbine might be too laggy.

Its going to be laggy as on my Rb25det. I guess it doesn't really matter used with launch control. Not sure if my fuel system is good enough for the maximum capability of that turbo, but will post result after I get it build and trailed.

Also was that VL on stock drive shaft? I abit concert it might bent or snap at that sort of power level.

yeh, has a one piece tailshaft and 31 spline axles..has done 70 odd passes though, although the gearsets(in the diff) are the weak point

having said that, the standard axles and driveshaft will last a fair while on slicks with a manual and forever with a auto

I only ever ran stock 28 spline axles and stock 2 piece driveshaft in my r31,never broke a axle, but busted the original

centre bearing in the driveshaft , reconned it and it was fine..auto though, they are soft on a drivetrain..

cheers

darren

Edited by jet_r31

Damn, well that kinda sucks Martin.. Does it feel the same? Did it make any less power with lower boost?

Like copycutter said, its all a process of elimination (a really f**king boring, tedious process sometimes :( )

I really wish I could get my hands on Martin's car.... I would love to pull the motor and just reassemble everything bit by bit.. Its GOT to have a f**king problem.

321rwhp @20psi. 4psi more boost has got me 30hp less than my previous tune.

No symptoms this time. Tuner double checked my cam timing, said I got it spot on. He even tried playing with the exhaust cam gear, but best results were where I had it. Set base ignition timing before it went on the dyno. IAT's are fine, not getting hot. It had no problems taking boost, it wasn't misfiring, it had plenty of fuel. It just doesn't make power. And I'm stumped.

That sucks. This is on BP98? Did the tuner have any comments on anything that he may have found suspicious?

When making less power than expected without misfires or any other obvious issues it is possible you could have one of these things happening (which the tuner will see). I don't clearly remember the history of your car so not sure if I am making redundant comments - sorry!

- Overly knock limited... this can be caused by all sorts of things, easiest to check or identify on your car would be to identify if the CAS triggering seems to be working properly

- Reaching MBT sooner than you'd expect (not due to knock - just not gaining torque as the timing advances) can happen if something is stopping cylinder pressures from climbing they should, can be a valve actuation issue

- Fuel demand lower than you'd expect, or falling over. I'd tend to put this down to a restriction, as it basically means your overall volumetric efficiency is down due to something - if you need less fuel than another car making the power you expect you should, and with the same target AFRs, then it means less air is passing through the system. You aren't going to make the power without the air flow required to do so

Just a couple of quick thoughts, may or may not be worth anything - but this situation of you having issues has been going too long and it'd be good to see you with a happy result so anything at this point can't be a waste, right? :)

very interested to se how the ss2 vnt turbo goes for the 330rwkw mark may be better choice then a t67 in my drift car if the response is there

Both billet SS2 and SLSS2 are more responsive with higher output then a normal T67. Check page 388.

The VNT model is targeting towards SS1 .64's response while making SS2's power. I will post further details as it gets installed and tuned.

That sucks. This tune on BP98? Did the tuner have any comments on anything that he may have found suspicious? When making less power than expected without misfires or any other obvious issues it is possible you could have one of these things happening (which the tuner will see). I don't clearly remember the history of your car so not sure if I am making redundant comments - sorry! - Overly knock limited... this can be caused by all sorts of things, easiest to check or identify on your car would be to identify if the CAS triggering seems to be working properly - Reaching MBT sooner than you'd expect (not due to knock - just not gaining torque as the timing advances) can happen if something is stopping cylinder pressures from climbing they should, can be a valve actuation issue - Fuel demand lower than you'd expect, or falling over. I'd tend to put this down to a restriction, as it basically means your overall volumetric efficiency is down due to something - if you need less fuel than another car making the power you expect you should, and with the same target AFRs, then it means less air is passing through the system. You aren't going to make the power without the air flow required to do so Just a couple of quick thoughts, may or may not be worth anything - but this situation of you having issues has been going too long and it'd be good to see you with a happy result so anything at this point can't be a waste, right? :)

Thanks mate, definitely appreciate any input as I'm completely stumped. Nothing crushes motivation more than being so sure you have finally found the problem, only to go even further backwards.

Unfortunately, my tuner said the car didn't miss a beat and was really easy to tune. It behaved perfectly, didn't show any signs of anything being wrong. If I hadn't told him that it was 30hp down from its last tune and almost 100hp down from where I expected it to be then he would have thought it went really well.

30hp would be in the expected range with a different dyno though wouldnt it?

Not really given the extra boost!

I know it's not PC to say in here but you have tried pretty much everything except for changing the turbo...

Yeh, I'd be willing to give it a go if it wasn't such an expensive exercise. The whole underpowered thing seems to have always been around on mine. Even on the stock turbo, I was only making 220rwhp @14psi. Then both G2's that I used only made 295rwhp. I had put that down to the stock ECU pulling timing and fuel, but now I don't know...

30hp would be in the expected range with a different dyno though wouldnt it?

It definitely feels slower now. It feels like my previous low boost setting. Quieter too.

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