Overboosting Help!

[n1neil]

Please help me. I have an r32 gtr with APFC, profec B spec 2, power intake, greddy piping, 3 inch exhaust, turbos rebuilt to nismo spec. Car is tuned for 320 kW on 18psi.

The Lo setting on the profec was set for 16psi and the Hi for 18psi both starting at 12.3psi, but they were a bit much; so I do most driving with the boost controller turned off but fuel economy with the boost turned off was shockingly bad.

I tried to turn down the Lo and Hi settings a whisker at a time to get 14.5psi on both Lo and Hi but with more gain in Hi than in Lo and with Lo starting at 10.1psi and Hi starting at 12.3. Bad move.

Now, with the boost controller on and off, it hits boost at 18.8psi at 4000rpm and is 23.2psi by 5000rpm. I have to drive my car under 4000rpm to prevent damage now as returning the boost controller to previous settings has no effect.

Please help me. This morning a ford xr8 boss ute overtook me!! in my gtr!!! *flabergastered*

[33VSPECII]

Contact your tuner??

[boostn0199]

Not a good idea play around with the boost controller once its been set i would only trust it being set on a dyno with WOT. Take it to your tuner will be under an hours work and tell him what settings you want.

[n1neil]

But it doesn't even go back to stock boost with the boost controller turned off. I thought something might have come unstuck maybe

[JonnoHR31]

check all the hoses

[Moodles2]

Depends on the solenoid type when unpowered, if it's a bleed type it would return to stock boost, if it's a pneumatic type you could see unlimited boost. Bleed types bleed air to raise boost, pneumatic types interrupt and block the boost pressure to raise it.

If a pneumatic solenoid's last position when powered was in a blocking position, you will get unlimited boost no matter what.

[JonnoHR31]

profec uses a bleed solenoid and should return to gate pressure when turned off

[R.3.2.G.T.R]

u got adjustable actuators? it might have been re-adjusted previously to run higher boost as stock, try lowering the gain until spiking stops

[SiR_RB]

Turning up the gain Too high will make u get major boost spike.

I wouldn't touch the boost controller unless it's on a Dyno dude, it's not worth the risk

[n1neil]

Now (on lo) 0%, 5% gain, start at 7.0psi, warning at 14.5psi, limiter at 5%. Boosts to 23.2psi then gates to nothing then reboosts then gates then reboosts then gates etc. The actuators are stock. With % at 0 and gain at 5% it should be at stock boost but it is boosting its tail out. There is a funny hissing noise under boost coming from the corner of the engine bay near the boost controller, closest the brake booster but I can't find any problems with hoses.

The boost hose that goes from the box that goes to the intercooler to the intake manifold has a vacuum hose next to it, on afore mentioned box, that doesn't have a hose clamp on it. Is it meant to?

My guy is overseas for 3 weeks but I don't want to keep it under 4000rpm till then.

[Moodles2]

Check the black box on the driveside firewall, that is a MAP sensor for the stock boost gauge, the factory hose often splits and will hiss under vacuum. The same hose goes to the back of the balance tube and can split there too.

Double check the hose to the FPR, if it's split there or came off.. bye-bye engine if you keep driving it.

[Room42]

My guy is overseas for 3 weeks but I don't want to keep it under 4000rpm till then.

That's terrible, how can you go on? On a more serious note find the cracked/disconneced hose and replace it.