Marshall

When pressurizing the side port on an external wastegate, is it normal for some of the air to escape because of the clearance between the valve and the valve guide? Its a Tial 40mm.

Thanks

crash course

strange that you have this problem also, because i am experiencing the same with my hks standard external gate. i don't know if that is normal operation or if maybe the valve/valve guide is just worn out from the metal to metal contact. i don't see how it could be air tight though because if that were the case then the valve would not be able to move up and down smoothly.
-ken

stylEmon

iTrader: (2)

It might leak when its cold, but with 700+ egts those parts might expand enough to seal up. Be interesting if you could try it with those parts heated up...

crash course

yes i was thinking about that too...i'll try it! still is kinda strange that this type of tolerance is allowed and i was actually thinking about machining out the w/g and installing a valve stem seal (similar to the kind used in cylinder engine heads) matched to the hks w/g valve stem. i think all the w/g manufactures do not use any type of seal at this end and i'm wondering if there might be a reason for that.
-ken

bobybeach

I wouldnt worry about it.
The amount of boost leaking from there is insignificant to what is being suplied by your compressor. Id say its normal with all external wastegates since it would be near impossible to properly seal that hot shaft.