turbo boosting problems

[david wrx02]

when i mash the gas it takes off as normal but after about 5 sec. the boost drops down to 7.5 then rises back to 12 and back down continues to to this up to the shift. it does his through out all 5 gears. now if i hold the pedal half way i boost to 7.5 and it stays there till the next shift. if i continue it has the same resolt through 5th gear.

[newtothegame]

Any mods done to the car?

[dragonfly]

Ive got the same problem with my car as well and we have changed the turbo,the boost control valve,the vaccume pipes,the actuator on the turbo.It still hasnt fixed the problem yet.But someone told me that the vaccume pipe from the boost control valve to the actuator housing might be faulty so change that.If it works Ill let u know.Hope some of the trouble shooting I did can work out for u.

[Jave]

have you tried a new restrictor pill line?

[dragonfly]

I just did that about half an hour ago and its still fluctuating...Only thing I can do now is work round the boost valve and see what to do from there.It has to do something with the piping or the unit itself.Ive also reduced the boost from the actuator rod to see if that helps but no luck.

[burtonboy759]

ive got almost the same problem on my rex too. it will boost fine in 1st and 2nd gear but once u get to 3+ when u mash the throttle itll boost to bout 17 and back down to 15 and flucuate between the two as long as its WOT. the boost is obviously not stock but im second owner of the car and have no clue what the previous guy did to the car.

let me know if u guys find a source for your problem itll help in narrowing down my problem source too!! im going to need to get it tuned at a shop eventually just no $$ at the moment.

[dumdum]

The actuator rod needs to be shortened/tightned.It's known as "boost oscillations".It can also be fixed with retuning the wastegate duty cycles.The stock BCS is a bleed type setup and also doesn't like higher boost levels.Depending on atmospheric conditons and your elevation (plus the boost level your running) it can't always bleed the pressure off fast enough.

[suby_doo]

having the same problem boost WONDERS BETWEN 10 AND 12psi have greddy profec b on high boost does the same on low boost too....NEED HELP REALLY PISSING ME OFF...

used to hit 18psi and hold before downpipe

mods- tbe, spt short ram, tbxs rfl

[dragonfly]

I just sorted out the problem I had.Ive replaced the vacuum pipes with heat absorbing silicon pipes and a new restrictor pill.I also cleaned out the BCS and the boost is holding really well with no fluctuation what so ever.Although I read the other posts and Dumdum had a good thing to add.Depends on the elevation ## running the car at.But basically if ## pipes have blocked the BCS from bleeding the air ul get that air almost recirculating which causes the boost fluctuation.Hope this helps....

[baller_v24]

good stuff to know, thanks for updating might help some people in the future.

are there alot of subies there in Africa?

[dragonfly]

No probs...Yeh we got quite a few out here.But none of em as kitted out as what u guys would have.They pretty much stock STI's and WRX's.But just having the car makes some sort of presence.hahahaha.Hope u guys do sort out the boost problem.I believe strongly in changing the vacuum pipes.Good luck

[david wrx02]

Ya I Just Ordered A Used Stock Turbo And I Hope It Gets Rid Of The Problem
Thanks You Guys If I Find The Salution I Will Pos A New Forem

[dragonfly]

Try getting the vacuum pipe with the restrictor pill in it and use that pill when u do change the turbo.I also recommend using silicon vacuum pipes with the pill in the pipe obviously.Thats what fixed my problem.

[03 CrazyTaxi]

Sounds like restrictor pill, BCS, and/or tune. I'd recommend the GM BCS and an Enginuity / Open Source tune.

Here's the BCS Part numbers.
GM Typhoon/Syclone Boost Solenoid, GM Part # 1997152
Pigtails, GM Part # 12102747


Just plug those part numbers into the search here:
GM Parts Direct: Your direct source for Genuine GM Parts