I'm using a TiAl 38mm external wastegate and noticed it was leaking exhaust gas the other morning. What I found surprising was that it was leaking from the flange at the exit side of the wastegate, so that means the wastegate leaks exhaust gas passed it at idle. Does anyone know if this is normal? If it leaks at idle, how much does it leak under boost???

Rich

 

Your wastegate should be fully closed at idle if I'm right.
When in boost it won't be leaking but it will be wide open allowing exhaust to flow through it. That's how it regulates boost, it relieves pressure, thus allowing the turbo to only spool to a certain PSI.
That is a pretty lamon explanation but I think it's right.
I think Tials can be rebuilt??

 

It's working correctly, my local dyno operator commented on the absolutley perfect flat-line boost control recently. But like I say, it's leaking at idle, enough for me to feel the exhaust gas coming out and see some condensation around the flange at start-up. I'll remove it this weekend when I fix the leaking flange and check it looks OK inside. It was brand new when the kit went on about 1K miles ago so I hope it doesn't need a rebuild

Rich

 

The Tial is really easy to take apart for inspection although I have never seen one fail. Are you sure its a real Tial and not an Ebay knockoff?

 

Does your wastegate vent into atmosphere?
If it connects back to exhaust before any restrictions (catalytic converter, muffler) could it be just the seal on wastegate exhaust side is leaking the normal exhaust backpressure?

hrk

 

It was bought from Ebay, but listed as a "real" one, not a kncok-off. The seller seems to sell a lot of them and has 100% +ve feedback, I hope he hasn't ripped me off!

hrk - the wastegate dump pipe connects back into the main down pipe before the cat. So you might be right about it being normal backpressure leaking up the dump pipe. I'll check it this weekend when I remove it.

Thanks for the help guys.

Rich

 

Thought I'd post an update on this. I took the wastegate off and cleaned everything, then realised that I'd been running it without the valve seat

It doesn't leak any more, plus I get full boost 900rpm sooner, so I'm happy. There's a pretty obvious moral to this story!

Cheers,
Rich.

 

LOL, I was gonna say that until I read this post