I noticed my performance seemed to be droping off while under boost. this weekend I decited to check for any boost leaks by pressurizing the intake. however the way I did thing gave me some very unexpected results Im hoping someone can tell me what I didn't consider.

Seeing how the suction side of my system is bound to leak some I wanted to bypass it all.

I dissconnected the tube at the intake of the intercooler, and installed my custom pressure cap. I basically made a soup can with a valve attached connected to my compressor. In theory this would be the same as applying boost pressure.

here's the problem When I did this Air came out the Y pipe air pump and intake filters. ???



I capped off the intake to the airpump ant tried again.

still leaking out the ypipe and air filters. WHY?
I could only get like 2 PSI on my boost gauge so whatever was leaking the air back to the turbo's must have been a OK size Vac line or something.

After looking all through the service manual, I couldn't find anything that would tie the main intake back to the turbo's.

Has anyone been successful at this?
what am I forgetting about?
what connects back to the turbo's before the intercooler?

 

i tried the same idea but i capped off both flexable tubes that go from the air cleaner to the turbos. i then pressurized the entire intake through the brake booster port. i was able to get 10 psi. i found quite a few leeks. if you dont seal the air filters pressurized air will go backwards through your turbos and out the air filter. not sure about the air pump lines. mine did not leak.

 

I tried this too at first. Most of my low pressure (ie vac.) lines elaked at a low pressure though. I wasn't intrested in fixing all those leaks though. the final kicker, the airpump was leaking around the shaft seal.

in order to avoid all the low pressure stuff, I wanted to just pressurize from the intercooler on. But something is leaking air back to the turbo's from the intake manifold.

 

You are pressureizing through the engine, in the intake to the chamber out the exhaust . Try this . remove the pipe to the throttle body elbow . get something to block that hole off, big rag folded up ,ect,ect, . Start the engine and warm up . Now quickly cover the hole completely . The engine should stop running quickly ,if it slows and runs on slowly then look for a leak .

 

I would try pulling the filters off and running the pressure test from there. There are quite a few lines that go from the lim to the Ypipe/bov (via the seq system)and intake (intake via the airpump crap).

Maybe its possible that they normally dont leak because when you have manifold pressure you also have pressure in the Ypipe ect so its pressurized on both sides creating a = instead of leaking. But since you ran the test from after the IC then its not pressurized on both sides of whatever is leaking therefore it leaks out into a part that is normally pressurized.

Just a thought/theory or whatever you want to call it.

STEPHEN

 

yeah I think Im going to have to resort to doing just that.
It only sucks because I don't have all my suction stuff plumbed to withstand pressure.