There is a vacuum line to it because thats how a bpv works, it uses the vacuum to open the bov. When your engine is reving it doesn't make vacuum, when you let go of the throttle or are at idle the engine makes vacuum. The bpv using this vacuum source to open, your thinking of a turbo car and a ecu controlled wastegate, the s/c is much simpler than that.

 

See, I am used to my car, which is turbo'd... so this is all new hash to me, lol.

I was thinking maybe a vac leak on the BPV would cause it to open too soon. BPV diaphragm is torn or worn. IDK. Any ideas how i could check it? Friend isn't letting us touch the car, soooooo. But, when I can get my grubby lil fingers on it, I am gonna flip the BPV to see if it has an effect.

Now, what is the normal VAC for a super'd car??

 

Yea you can't a turbo car is the same as a supercharged car. Sounds like you may have a vw? Anyway vac on idle should be around 30mmhg just drivng easy i think its around 15mmhg.

 

I have a turbo Cobalt. Anywho...

So, it is idling right now at 20mmhg. Cruising is about 10mmhg. When it was running better it was idling around 13mmhg... cruising (about 2k rpm) was about 0 psi. IDK what this cars deal is. If it boils down to it, I will take a whole day and replace every damn vac line in the entire car. If thats not it, I will try a vacuum canister, and if thats not it, I will try a stick of dynamite.

Something has to give. But what is it...

 

Well, reversed the BPV, and it still ran ____ty. I guess I wish I knew if this was running normal or not, and if it is normal, why it was running like it took crystal meth the other day after the battery died.

 

well then my money is on the belt slipping...and the day it felt fast was the day it didnt slip...a slipping belt is common on s/c

 

Don't you think you would hear it though? I know its common, but wouldn't it be boosting inconsistantly? I mean, it doesn't build boost good, but it builds the same amount of boost time and time again.