Porting Wastegate (how many mm?)

[texaselite]

Going with a 2.25" piper stainless exhaust with sports cat and ceramic downpipe. Also going to install Everest chip.

While the mechanic has it (for this and a whole slew of other things) --- any reason NOT to have him port the wastegate? Any downside to porting if I haven't driven it and tested for boost creep? Also, when I ask him to port, how much should I tell him to port?

[epipete]

A search on 'Porting' brings up 28 pages of wisdom some of which will answer the question of how much, failing that there is a whole topic dedicated to porting in the Wiki, look under 'Porting'!

The consensus and wiki suggest 20mm but some have gone for 21mm

[texaselite]

Thanks, is there a downside to porting w/o necessarily experiencing boost creep?

[ashm]

I can't think of any downside. You might get a bit more leakage around the wastegate flap, but not enough to limit peak boost. You'll also be slightly weakening the wastegate manifold, but again not much given that there's plenty of metal left when you're done. If you don't do it on the bench you may get grinding grit into the turbine, but that shouldn't be an issue if you keep things clean. The only downside I suppose is that he'll charge you to do it, but you're quite likely to need it done if you're going for a much freer exhaust.

Adam

EDIT: there is a downside to the whole Piper/Everest package - you'll go through a lot more tyres and fuel, and your face will hurt from grinning...

[paulsmithmk]

EDIT: there is a downside to the whole Piper/Everest package - you'll go through a lot more tyres and fuel, and your face will hurt from grinning...

[rip]

Thanks, is there a downside to porting w/o necessarily experiencing boost creep?

The wastegate's standard size is matched to the exhaust so that the ECU has as much control as possible.
Many of us have created a mis-match by fitting larger systems which allow higher exhaust flow.

If you port the wastegate then go back to your original exhaust config then the wastegate will only have to open about 40% to control the turbo sufficiently. It would be almost like a tap which can either be fully open or closed but nothing in between.
That's the theory. In practice the difference is probably insignificant.