I have a significant boost leak- only when the secondary turbo kicks in at approx 4k rpm. It is heard on the right (passenger) side of the engine. I have the Efini y-pipe in place and all rubber connections are replaced with hard pipes. Where would you look for leaks? I intend to check the o-ring on the y-pipe, but I am puzzled why the leak happens only under secondary boost.
Ron A.

 

That's pretty common actually, search on that issue and you'll see.
But check the following:

* The vacuum hoses on the pressure chamber.
* The vacuum hose on the one-way check valve.
* The vacuum hose that goes into vacuum chamber.
* The vacuum hoses that go to turbo control solenoid.

 

Check both 10mm nuts that secure the Y-Pipe Flange to the Secondary Turbo Housing.

 

It could be the rubber O-ring where the #2 turbo collector and the Y-pipe join.

 

Quicksilver rx7 said "It could be the rubber O-ring where the #2 turbo collector and the Y-pipe join."

That is my first guess. The leak is as bad as when the factory rubber connector is cracked- very loud. I've had the Efini y-pipe on the car for a couple of years, so I guess the o-ring could have dry-rotted and then broken into pieces which eventually blew out. Hope that is it.

 

hm i think this is the same prob i have. i can hear a lot of air moving under the hood while in boost and im only getting like 4 or 5lbs boost. i thought it was a blow off valve stuck open or something, but ill check all that stuff. thanks

 

If it only happens when the secondary turbo comes online, then that may not be it. The Y-pipe o-ring is on the primary turbo side of the charge control valve, so you'd still have a leak with the primary turbo if the o-ring was bad. I'd check the Y-pipe connection at the secondary turbo as well.

 

imw illing to put my money on this one.. I had similiar problem before.