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Still bad boost spikes, checked and changed everything...

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Boosted97GS-T

20+ Year Contributor
90
0
May 1, 2002
Louisiana
heres the deal, for about a year now i have been having huge boost spike issues with my car. But since i never had a need to run more than 15psi it never bothered me. Now that i have upgraded turbo and other supporting mods, i would like to pick up the boost to around 18psi or so. but no matter what i do it 15-16psi.

I checked for boost leaks, and everything seemed fine except my 1g bov was leaking a little so i changed out that with a turboxs bov.

checked leaks again and everything held great. went for a test run and spikes went down to about 4psi spikes.

just yesterday i changed out my joe p mbc for a hallman(nice looking mbc i might add), and still have the same exact problem.

from what i can tell it looks like it likes to be at 15psi, the more i pick it up the more it spikes. sometimes the spike last long enough that it will give me fuel cut, but most of the time it will just end up back at 15psi or 16psi.
 
and another thing, when i bypass the mbc and just go straight to the wastegate, i get 12psi with no spikes all day long.
 
How much vaccum hose do you have?? Try to keep the lines as short as possible. That will help.
 
i tried everything from a foot to about 3in. going to the wastegate, and i had no change.

how would i check the wastegate actuator?
 
Check your wastegate actuator. Make sure your actuator rod is set to the point where the wastegate is fully closed. You can give FP a call and they can probably solve your problem over the phone.
 
How is your exhaust setup, I used to get spikes on my T-25 but when I change to the B28 I can now hold boost as low as 10psi with NO spikes. I am running 2.5 DP, stock cat and 2.5 exhaust. With only port wort done to the turbo.
 
ok, i shortened the hoses even more today, even zip tied them and still have exact same problem. i lowered it for the time being and boost jumps to 17psi then levels off at 12psi.

also i stayed side by side with my buddys 97 cobra even at 12psi :)

i have 2.5" exhaust with a test pipe, and also a evo o2 housing, i think i'm flowing enough exhaust
 
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