Does anyone have advice on adjusting the bypass valve to allow full potential boost, or to allow full boost sooner than what it is currently configured to?


I've read on other threads of people hitting 12.5-13psi. Even 1psi of boost can make a good hp difference.

You may very well get the boost to come on sooner, but the PCM can also vent extra boost and override the calibration on the bypass valve.

First person to get around this loop hole w/the bypass valve(on our cars) and succeed without blowing there motor up and run 18PSI on the stock Eaton blower gets a gold star in my eyes. ;)

Where is the BPV located??

Where is the BPV located??
It is attached to the SC on the right side.

we ran 13 psi on our cobalt by removing the vacum line on top of the valve and moving the one on the bottom to the top. a few weeks later it = check engine

we ran 13 psi on our cobalt by removing the vacum line on top of the valve and moving the one on the bottom to the top. a few weeks later it = check engine



my ss is boosting 13lb stock,but it,s got a few thousand mile on it :cssNET:

I cant wait for an ECU to come out for our cars. Then we'll beable to adjust whatever we want to.

we ran 13 psi on our cobalt by removing the vacum line on top of the valve and moving the one on the bottom to the top. a few weeks later it = check engine
Interesting, how did the tubes effect the psi exactly? Did it allow boost full time instead of it being based on engine load?

Interesting, how did the tubes effect the psi exactly? Did it allow boost full time instead of it being based on engine load?


we were getting boost instantly from the moment you press the gas pedal.

Why would GM do something like making the ECU so tightly locked and not release any upgrades for us? They tend to leave their best people out in the cold it seems. :mad:

we were getting boost instantly from the moment you press the gas pedal.
Hmm, did the CEL turn off when you reconnected the lines to where they should be? Also, would you say theres a performance benefit to running full boost all the time?

Hope you don't mind that I keep bugging you about this ;)

MarcS you ask if there's a benifit in running full boost all the time, right?? How can you get full boost all the time??? Boost is related to RPM when you are running a belt driven SC. So adjusting the BPV would only help throttle response (instant boost)

Unless I don't understand this roots style blower fully you'd have to get the rpms in the upper 5000's to get full boost. How I'm understanding the cobalt is that the BPV 'should' close once there is no vacuume (WOT), and then the PCM would then sense manifold presure some how and if it exceeds a pre determined threshold it would then open the BPV to vent the excess pressure. Correct??

MarcS you ask if there's a benifit in running full boost all the time, right?? How can you get full boost all the time??? Boost is related to RPM when you are running a belt driven SC. So adjusting the BPV would only help throttle response (instant boost)

Unless I don't understand this roots style blower fully you'd have to get the rpms in the upper 5000's to get full boost. How I'm understanding the cobalt is that the BPV 'should' close once there is no vacuume (WOT), and then the PCM would then sense manifold presure some how and if it exceeds a pre determined threshold it would then open the BPV to vent the excess pressure. Correct??
Ah, I'm sorry I didn't mean full boost as in 12psi. I meant full boost(instant boost) as in boosting all the time instead of being regulated by the bypass valve. Hence, the SC boosting into the engine "full time" and not into the atmosphere.

No, you're right. Full boost can't be acheived until you're in the upper rpm's. Sorry for the confusion.

Yes, Camaro, you're right. The BPV closes when you're WOT. The piston in the valve housing closes when there's no vacuum to hold it open, letting "full boost" into the engine.

Where is the BPV located??


The actual valve is inside the eaton, but the the actuator is a little black cylinder with vaccum lines and a metal shaft that moves the value.

Give it time on the PCM . Like every new model that comes out , it takes a bit to break into . The aftermarket had a hell of a time with the C6 PCM too . Plus GM is wanting a slice of the aftermarket as well , hello GM accesssories ....with what I understand to be performace packages for the SS . There is probably MUCHO to gain though just in tuning the PCM and a better intercooler or something like coolmist , and leaving everything else stock . Given it supercharged , the stock PCM is proabaly tuned WAAAAAAAAAAY on the safe side of things . Good for longevity , not as good for performance . Itll be interesting to see how easy this thing respnds . I havet touched a thing on mine yet , AMAZINGLY :lol:

Along with the tuning that comes along with a new PCM, our SS/SC's could really benifit from having the rev limiter raised from 6600 rpm or so to about 7200 rpm. These engines scream for more revs.

You think that with GM making a performance car that they wouldn't put that many restrictions on it..... damn ecu