R34 Gtt High Flowed Turbo... Can't Make More Than 260hp

[Xerxes]

Hi Guys,

I recently had my stock turbo compressor wheel disintegrate and at the time my mechanic advised to get my turbo high flowed and we sent it off to get it done. Turbo arrived back with bigger cores, steel wheels, etc and the guys who did it reckon it can now handle up to 320hp at the wheel. My mechanic fitted it back on and straightaway with not much tuning it was making 260hp at the wheel, but didn't have any low-end response. After many hours spent with the tuning he was able to get the power to come a bit earlier but it would still reach 260hp (at around 5500 rpm) and then taper down a bit. Unfortunately I don't have a dyno graph handy to show you guys and I'll try to get one as soon as possible.

R34 GT-t

My mods:

- High flowed turbo

- Trust/Greddy front mount intercooler Spec-V

- Apexi PowerFC

- Greddy ProfecB spec II boost controller

- SARD 650cc injectors

- Tomei fuel pump

- Z32 afm

- pod filter

- hks sequential bov

- 3" fujitsubo turbo back exhaust with high flow cat

The problem is no matter what settings the car is tuned to, it won't go past the 260hp mark (this is at 19psi). We also found that the turbo was making 23psi at the turbo...but by the time it is entering the inlet mainfold, the boost reading was 19psi. This happens from 5500 rpm to red line. We have checked the intercooler piping to ensure that there are no leaks. We even disconnected the exhaust from the dump pipe onwards and there was no appreciable gain. My mechanic seems to think that the intercooler might be the bottleneck as the loss of almost 4psi from turbo to the inlet manifold is hurting the top end.

Does anyone have any suggestions as to what might be the bottleneck? Once again I apologize for not having a dyno chart as that would make it make the problem more evident. I'm going to try and swap the intercooler with a friends later on in the week to see if that makes a difference, but in the meantime if anyone has ideas or tips on what else I can try/look out for that would be great.

Cheers.

Edited August 23, 2008 by Xerxes

[R32 Driver]

what ecu are you using?

[Xerxes]

what ecu are you using?

Opps forgot to mention, Apexi PowerFC

[wolverine]

who did the hi-flow?

[Xerxes]

who did the hi-flow?

Not sure, he was a contact of my mechanic's

[wrxxy]

check your base timing!

[VB-]

i would change the cooler for sure, but if your still getting 19psi in the manifold, should be making more power than 260hp. have you got a plot of boost etc. you may have an actual boost leak also, have you checked all clamps etc?

[R31Nismoid]

Well you have a intake restriction. Usually the cooler or the bends and so on.

It also depends on the hi-flow, who did it... what specs etc etc.

Without knowing that its hard to say

[sloutch]

Some of the R34 owners with high flows get between 240rwkw to 270rwkw. Better to check your turbo as well.

Fuel mods seems to be right.

[Tangles]

the exhaust is a restriction to an extent in my opinion

also - completely seal the pod filter in a custom CAI box

replaced my "fujitsubo' muffler with a Kakimoto hiflow one, and got better cat converter.... much better flow for my hiflow turb'

suggest you look into it (ie dyno with exhaust dropped off at front of cat converter, see the power difference with on / off

[666DAN]

Any development on this???

What has been swapped/tested/eliminated?