I've got a T04B Turbo with an external Tial 38mm-Wastegate in my RX7 Turbo II and since yesterday i've got a weird problem with the boost pressure. The car runs great with normal boost till round about 6000rpm but if i try to get higher than 6000, the boost pressure immediately goes down to 0psi.
What the hell could be wrong here? The car was running fine for about 8 weeks and then this happened.

 

Check for boost leaks.

thewird

 

Do you really think it could be possible that a boost leak causes the boost to drop from 10psi to 0psi exactly at 6000rpm?

 

yup

 

The same could be said about your wastegate theory. Boost leak tests can find other issues as well. But to answer your question, yes its possible.

thewird

 

Wow. Didn't thinks so but i'm going to search for leaks tomorrow. Any suggestions where i should start searching?

 

does it feel like its misfiring at 6krpm?

 

No. It's just losing all the boost pressure but keeps getting faster. It's not the fuel cut.

 

could also be the backpressure over powering the wg spring and opening it.

 

Which would cause more boost, not less. But that does bring something else to mind, do you have a cat on this thing? Could be clogged.

This is how you test for boost leaks... (normally you put a gauge on it to see how much pressure your putting in). Crank it up to 20 PSi and see what blows off and/or leaks.



thewird

 

by over powering i meant pushing the valve fully open, venting all the gases.

 

Whatever pressure is being applied on the wastegate, is also being applied on the turbo.

thewird

 

I've got a cat on the RX7 but it's brand new and it's a 100 cpi one so i guess it should be ok. I don't think the wastegate can be pushed open because of back pressure the way i connected it. It's connected to the manifold on one side and to the downpipe on the other side so it should really get always the same pressure as the turbo.

 

If not boost leak (reasonably likely), rag in the intercooler is a good one, gets picked up when you reach that flow level consistently, or soft turbo inlet pipe/filter collapsing on itself.

 

Didn't have enough time for vaccum testing til now but i found out i've got a blown seal between the manifold and the turbo. I ordered a new one today. Might that cause my problem?

 

Problem solved. It really was the blown seal. Amazing how much trouble such a sall piece of metal can cause.


Thanks for all your suggestions and help.