AJT

*Posting for a non-internet inclined buddy*

He's recently changed his setup on his 3rd Gen rx-7 (Heavily streetported) from a T3/T4 w/ SS Autochrome manifold using a 38 mm Tial wastegate to a new setup (T4 60-1, using SS Autochrome 40 mm wastegate). HKS boost controller. Had no problems with the old set up, now the boost is completely uncontrolled. He's tried a different wastegate spring, tried the old Tial wastegate, even tried running the wastegate feed directly to the wastegate and bypassing the boost controller to just run off of the spring. Doesn't matter what he does, he can't get the boost under control. The boost gauge just swings up until he lets off for fear of popping his motor. He's got a 3" DP and full exhaust. I've tried to search but didn't have much luck. Is the wastegate feed from the manifold just in a crappy spot? The only thing he can come up with is that the last, small, turbo created enough back pressure in the manifold to push the exhaust out of the wastegate when it opened up, but with the new, much bigger, hot side that it's not really creating any sort of back pressure to do anything when the wastegate opens up...

Does that make sense?

Anyone have any other suggestions? They pressure tested the wastegate and it opens appropriately... The pressure line that he uses for the WG he also has tapped for the boost gauge, so he knows it's getting pressure, he's also just run the line straight to the wastegate w/o tapping for the boost controller with no luck...

AJT

Anybody?

AJT

Thanks for all the input!

cewrx7r1

iTrader: (2)

I would say that something is not hooked up correctly or some switch not in the correct position. Is the booost controller set up for internal WG instead of external WG. These type of errors are usually operator errors.

ErnieT

iTrader: (2)

You pressure test everything else for any other leaks? You check the fabric gasket inside the wastegate for tears? Exhaust manifold cracks?

Thats not a big turbo so that wastegate should be fine. I would look elsewhere.

AJT

BC set up for external WG. As previously mentioned tried both the 38 and 40mm wastegates. The WG dumps to the atmosphere, and I'm told he can hear the wastegate open up at 8psi (spring pressure) but the boost still spikes and holds well beyond that before he lets off. Is it that the WG is too small or that the manifold sucks? He's considering just taking off the wastegate and making a short (but loud) trip down the street. If he still boost spikes I guess we would know that it's the positioning of the WG rather than the WG being to small since the exhaust would have an open path to exit the manifold before getting to the turbo...

AJT

Everything's been pressure tested very carefully. There no leaks/cracks to be found and if there were wouldn't it only lend itself to the car not creating enough boost rather than generating uncontrolled pressure? I guess I'm trying to figure out if the wastegate's too small or the feed to the wastegate on the manifold is a poor design...


ErnieT and cewrx7r1 I really appreciate your help!