Oh...and this is important- you may see big KR- full boost on a 3.4 pulley is alot different than 3.5/4 PSI- if you start seeing KR back off right away- don't blow up your engine!

 

Correct me if I'm wrong but if I disconnect that vacuum tube the bypass won't relieve pressure will it? I could blow my engine the first time I step on it.

 

You're wrong. The vacuum line attached to the manifold will vacuum activate the valve- furthermore, even if both lines are disconnected the valve won't stay CLOSED, it'll stay OPEN (which is what is happening to you right now) and you'd see 3.5/4 PSI max boost. Otherwise there'd be alot of blown up L67s out there.

FYI, my Monte has no BBV solenoid- it's operated off of manifold vacuum only.

 

Probably won't blow it on a 3.4 with those mods. All you need to do is bypass the bypass valve and let her rip. I'm thinking closer to 8-9 PSI with those mods.

Either way you shouldn't hit any destructive KR.

 

If we're talking 8.4:1 compression (L67) then I'd agree. But, there's a huge difference between an L67 with a 3.4 pulley and an L36 (9.5:1) with a 3.4 pulley. It'd be pretty easy to get massive knock with a 3.4 on an L36 without a solid tune and serious supporting mods.

Regardless, I agree that he needs to figure out his missing boost problem before he does anything.

 

True, but he also has a custom tune which resulted in 0 KR so bypassing it to see if he can break 3.5 PSI shouldn't be a problem.

After rereading the original post though I do need to ask for more info to find out if the tuner was an idiot. When the car was custom tuned, did you get 7-8 PSI and this 3.5 PSI is a new problem or was it tuned did it only goto 3.5?

Also to goto that 3.2 pulley start looking into an intercooler (best option) and getting a bigger cam.

 

You're probably right, but I didn't want him getting too comfortable with the idea of dropping pulleys too quickly on his higher compression setup. I bet that 3.4 does knock a bit as it sits right now once he gets full boost back.

 

you are definitely having an issue with your BBV. get that fixed and go have some fun! it's amazing how much of a difference doubling your boost can make. as far as the tune, my guess is that you have a different year tb (and maf) than the pcm order was for. the MAF charts are quite different for certain year MAF's....i would richen it back up to 11.4-11.5 or so, 11.8 is a little aggressive on a 3800, there isnt really power to be had by running it that lean, and you are better safe than sorry!! in our experience, leaning a SC 3800 past 11.5 or so picks up almost no HP. our cobalts on the other hand, leaning them out to 12.20's usually picks up like 10 whp....

 

^awesome to see a ZZP rep on here.

And nice numbers on that GP!

 

I tried replacing the BBV actuator and saw the same amount of boost on my gauge as well as on some dyno equipment so I know it isn't the gauge. The guy at the dyno who tuned it suggested dropping the pulley to see if boost goes up.