32Gtr Bogging Down Through Rev Range

[joeyta22]

Hey guys,

I seem to be having a little bit of a niggling drama with my 32gtr and after some opinions.

The engine has had rebuilt bottom end with tomei cams + gears, -7 turbos with gcg 1bar actuators, profec b boost controller, power fc and all the other supporting mods make 320kw at the rears.

Driving around the car feels great, coming out of corners and such it pulls really nicely; however the problem i'm having is when powering through the gears from standing start (drag race for example) the car seems to really bog down/seem like its over fuelling from second gear onwards. It seems to drive fine, reaches boost and rev's cleanley with no stuttering or anything but just feels really laggy and the power's not there (drag time proves it aswell with a fastest time of 12.8 after multiple passes and i know there are alot of other factors at play but lets just say for arguments sake that it launched great and shifted near peak power each time with very minimal wheel spin).

Initially i thought the standard actuators might be the problem, so i bought the upgraded gcg 1 bar actuators and even pre tensioned them about 5mm or so and also purchased the profec b for its gain ability which i thought would help. After fitting these and getting a tune from a very reputable tuner, the car still has the same problem (afr's on the dyno sheet were spot on and boost didnt spike with a peak 18.8psi). After chatting to the tuner, he said to try pretensioning the actuators another 5mm or so as the boost curve did showed it was coming on a little late, and this would make sense of why it feels so laggy/boggy/over fuely.

What are peoples opinions? I would have thought that the actuators with a base of 1bar and pretensioning them on top of that already along with the gain control and reputability of the profec b and reasonably small -7 turbos that it would have come on alot earlier. Anyone else had similar expeirience or any idea what else the problem might be?

[SiR_RB]

does it feel like hesitation between gear changes at high revs?

my old gtr had the same problem and that had -7's and profec b aswell, but i was running 8psi actuators so i thought it was that....never got to the bottom of it

[joeyta22]

It does feel like once ive changed gears (at high revs) that it takes a while for power to pick up again and just doesnt feel very crisp (for lack of a better word).

Just thinking in my head, ive heard once before with the rb26's that you really have to roll on the throttle very slowly as opposed to just foot to the floor as soon as possible after each gear change like you would with most other cars/engines... any truth to this, or just BS as i thought at the time.

Edited June 1, 2012 by joeyta22

[SiR_RB]

sounds exactly like the problem i had, even with almost 300kw at the wheels it wouldnt even chirp seconds because of the hesitation between gears, felt like almost 1 second or so for power to surge back on...

have you tried ur low boost setting? does it still do it?

mine didnt have this problem on low boost at 16psi only high on 19psi

Edited June 1, 2012 by SiR_RB

[STATUS]

when we get the dyno back on-line after the upgrade feel free to drop past and we will do a few tests.

[Sinista32]

Keen to see the cause and fix posted.

Picked up something similar when upping boost from 18 to 21psi

[linkems]

Is your car making stable boost? Is it running 18psi consistently or does it drop when your car feels sluggish?

what is the air intake temperature hitting? computer could be pulling timing out

[joeyta22]

when we get the dyno back on-line after the upgrade feel free to drop past and we will do a few tests.

Cheers Trent, i'll try to keep an eye/ear out for when its all up and running

[joeyta22]

Is your car making stable boost? Is it running 18psi consistently or does it drop when your car feels sluggish?

what is the air intake temperature hitting? computer could be pulling timing out

boost is stable as per pic of the graph in the first post. Im not really able to keep an eye on the boost gauge whilst its all happening, but on the recall feature it makes the target boost.

Not sure on intake temp, i did make a shielded air box for the pods with dual cold air intake as it does seem at night to feel alot more lively when cruising around. That being said though, at drags and such it was pushed around and only started up near the line and even during the night it still has the same problem, so intake temp shouldnt be high enough to cause much of an issue i would think.