Porting internal wastegate
 

Wasn't sure which section to put this in, just wanted to share my experience + pics to help anyone else along in the future.

Received my FM turbo kit yesterday w/ 3" exhaust. I've read that boost creep can be a problem, especially if wanting to run 6-7 psi. I'm wanting to start out at that range for initial tuning, then tune my way up to ~10-12psi, whatever works out to ~225-230ft/lbs on the dyno in the interest of keeping my stock block intact.

I talked with a couple guys at FM, they recommended against (and said their supplier recommended against) porting the wastegate for boost control. After completing it, I can understand their recommendation against it for the "average" user as there's quite a bit of leeway to mess things up or get hurt if you aren't careful.

Tools: I used an air grinder, TEMO SC-3L6 carbide burr (Amazon had it for like $17 after shipping fees), eyes/ears/gloves/breathing protection (you don't want get this stuff in your skin/eyes/lungs).

Here's the stock port:
https://www.miataturbo.net/attachmen...1&d=1354716115


And here's the results after about an hour of work:
https://www.miataturbo.net/attachmen...1&d=1354716115

https://www.miataturbo.net/attachmen...1&d=1354716115


It makes a nice smooth transition into the flapper now. One thing to be extremely careful about is not taking too much off the lower edge (bottom in these pics). I almost went too far, and it started eating into the seating edge for the flapper (more easily viewed from the other side, which I don't have any pics for unfortunately). Mine was paper thin at that point until I broke off a bit of it by hand to make sure it didn't come off during operation later. After cleaning it up I'd say I went from ~1.5mm spare seating material to probably 0.3mm. I know Begi recommends not touching this area, as it's possible for the flapper to get jammed up during closing due to slack, but testing it 100 ways/angles/variations it still smoothly closes without snagging on the edge. It still seats enough that no light can get through, so I'm hoping I didn't get too carried away.

Hope this helps someone else out who's thinking of doing the same thing. One interesting thing I noticed was the bolts holding the turbo to the manifold (inconel studs w/ locking/retaining hardware), and downpipe fitting to the turbo were fairly lightly torqued. I snugged them up slightly tighter than they felt coming off, I'd guess they were probably tightened to 15-18 ft/lbs originally, and now they're around 22-25 ft/lbs. Dunno what anyone else is using, let me know if there's some issue with snugging them up a little more.