Too much boost!??

[newsh]

I've had an unusual problem the last couple of days actually.. Too much boost!! At part throttle the car boosts to 1 bar as normal (Car has a 1Bar spring) However, if I floor it instead of 1.8 - 1.9 Bar it shoots up to 2.2 - 2.3 Bar and then sounds like the ECU retards the ignition or cuts every other spark and it makes a horrible growling noise and shuts down. No overboost cutout just horrible misfiring So maybe a wastegate problem or WGFV sticking or ECU? Not sure.

As the car boosts normally at part throttle it seems like the WG Diaphragm is ok, also the WG plumbing.. What would cause the boost to go so high?

[Jamo]

Nip had this and it was his dump valve IIRC

[Rusty]

Have you disconnected the WGFV? That will be the real test.

[newsh]

Good point, why didn't I do that before taking it to Pete's..

[EspenW]

I would guess that the N75 is leaking. Had the same thing happen on mine, and I've heard horror tales from plenty of others. Can blow the engine in no time.
N75 isn't very trustable over 1.7 bar.

[newsh]

Yes. That would make sense.

[newsh]

Seems it was the frequency valve

[EspenW]

Just as expected. These things are risky in a setup that boosts more than 1.7bar.
Folks think their setup is safer with the N75 (ECU able to pull boost), but the valve is so unreliable it is scary. I feel way safer with my mechanical boost controller. Pulling boost is only the ECU's 3rd line of defence against detonation.
The boost solenoid used on the GMC Typhoon is supposed to be a lot better. I got one of these as a part of a two stage boost setup in my car (flip a switch between 1.2 bar and 2.0bar)