3 replies to this topic

[TheStotts]

Recently had an Astra VXR turbo fitted and the car feels fantastic (manic!) but I have concerns over the level of overboost. The garage that fitted the turbo have wound the nuts right to the end of the actuator thread but the car is still overboosting to 15psi. It then settles back to 10-12psi. Is it just the mechanical action of the actuator that controls the overboost? I know that one of the solenoids controls the level of held boost but can the solenoids also play a part in the level of overboost? Is it worth trying standard Z20LET actuator/boost solenoids? As far as I know the car has not been mapped. Thanks for any advice

[Bumblebee]

Think 10-12psi is standard,I think stage 2 peaks at 20psi and then settles at 17 psi

Edited by Bumblebee, 08 April 2013 - 10:16 AM.

[VXT_NI]

I believe It's mostly an action and consequence of the boost solenoid that determines the level of boost overshoot. The ECU will cut and go into 'limp home' mode if the overshoot is too much and cant be controlled. Nothing to worry about then :-) If this is a recent addition, I would give the ECU time to re-learn the required PWM values for the boost solenoid, as it uses the 'target/actual' method of control and the ECU will attempt to smooth out the peak over time. Hope this helps.

[TheStotts]

Think 10-12psi is standard,I think stage 2 peaks at 20psi and then settles at 17 psi

That’s interesting, thanks

I always though stock levels were far lower. Can anyone confirm if these levels are correct?

Extract from Thorney post, on September last year, said:

Standard VXT will boost to 9.5psi and hold 8.5-9psi
TMS Stage 2 VXT will boost to 15psi and hold 14-14.5psi
TMS Stage 3 VXT will boost to 18psi and hold 17psi
TMS Stage 2 VXR will boost to 17psi and hold 16psi
TMS Stage 3 VXR will boost to 19psi and hold 18psi

From here http://www.vx220.org...boost-pressure/

I believe It's mostly an action and consequence of the boost solenoid that determines the level of boost overshoot. The ECU will cut and go into 'limp home' mode if the overshoot is too much and cant be controlled. Nothing to worry about then :-)

If this is a recent addition, I would give the ECU time to re-learn the required PWM values for the boost solenoid, as it uses the 'target/actual' method of control and the ECU will attempt to smooth out the peak over time.

Hope this helps.

Thank you. Yes it’s a recent change and the battery was disconnected for installation so it may well still be in the learning period. Is the general consensus then that the car will be safe as the ECU will go into limp mode to protect the engine? It’s nice having the extra performance but I don’t want to risk running lean