im porting my wastegate tomorow and was unsure how exactly the size is measured. i was thinking it was diameter, like most other things, but 40mm seems pretty big compared to the size of the turbo. anybody know for sure?

 

damn can you port the stock wastegate that big? Iv'e seen it 38 or so but that doesn't leave much material left.

 

a few people have gotten it close. im planning on something like 35-38, whatever i end up with. and leaving 2-3mm for the flapper cover to rest on.

 

http://www.aaroncake.net/rx-7/s4wastegate.htm