Only 7 psi boost! Plz help
 

03 wrx fairly stock, Prodrive backbox, forge dump valve, decat up pipe no map that I know of. Idles a bit rough n low but that’s another issue n fairly common i hear.

Max boost is 7 psi even up hill in 3rd or 4th (under load so 4K rpm)

Checked n changed boost controle solinoid - no change
Disconnected wastegate actuator and plunged the line line - got high boost so backed off with the presumption this means turbo boosts fine n no leak in vac line or dump valve!?
Compression test done - all good

As far as I am aware 7psi is the wastegate pressure so I guess this is opening for some reason.

Any ideas why or what I do to test next?

Sorry for repeating a common problem but wanted some thing specific to what I have done to date. I’m no mechanic so really appreciate any assistance you could offer.

I have been to two specialists one says to do a data log but I fear this will b same as the compression test and not really solve anything. Another said to adjust the wastegate arm but if it’s releasing at 7psi it’s working correctly?!?

Please help me!

Do you have the correct spring fitted to the dump valve and is it staying closed under boost?
AFAIK the Forge ones come with two types of spring you can fit.
Have seen so many BOV related issues at the local rolling road and it's normally because the valve is opening when it shouldn't or is stuck partially open. Forge is normally a good make but worth a check.
A competent mapper or specialist should be able to point the finger to the culprit.

Rough idle can be caused by a number of different things, search on here will throw up some ideas. Good luck let us know how you get on.

Thx mr Noisy,

I have disconnected the wastegate n hit high boost levels so I thought this indicated an air leak is not the cause?

Also checked guage n it’s working correctly and changed wastegate actuator n tightened it as much as it would but still only 7psi maybe 8 now.

I think doing a data log run is all I can do now to try and figure it out.

Have noticed the T fitting between turbo n wastegate actuator only looks about 2mm which I believe should be bigger so might try changing that as I think it should be 3 or 4mm but I don’t know if this would be the cause of the problem or not?

That's not the cause if anything that would increase boost is your pill still in place between the turbo and the T piece.

yeah Pill is there, im thinking there must b a sensor playing up telling he ECU to cut boost to wastegate pressure only.

no engine management light...