Overported wastegate by less than 1mm...leave it or suggested fix?

Hi guys. I was porting the wastegate on my turbo that will be going into my Miata, and made a classic rookie mistake of overporting in one corner. I accidentally ended up overporting it by what looks to be less than 1mm more than the flapper door (picture and video attached). As you can see, light passes through that one area. The video is a better representation of it, as the picture actually makes it look a little larger.

Am I going to see any issues due to this, and if I am, what are my options to fix it? I'm a bit stressed about it, but all I can do now is figure out if its an issue and what to do, so any help is appreciated!

https://youtube.com/shorts/aawoRPspyhE?feature=share

I assume that's the part where light is shining through? I would expect that to be a mini boost leak.

BoxheadTim said:

I assume that's the part where light is shining through? I would expect that to be a mini boost leak.

Yep its right where the light is shining through. Do you have any tips on sealing that up? I'm at a loss on what I can do to seal it up, I'm not sure if a welder might be able to add material to it for me. Its pretty small so wouldn't take much, but I'm not sure how easy welding the housing material is.

Whoo boy. What's the diameter of the flapper? How about replacing it with a larger one?

I had a turbo once where the wastegate port was a little too big for the flapper. It just barely covered (couldn't see light through it) but the edge of the flapper would catch on the edge of the port sometimes, so it wouldn't always close all the way. I was able to find a flapper that was just slightly bigger, and it solved the problem.

Actually, just looked through my eBay purchase history and found it. This is the one I used: https://www.ebay.com/itm/161051084308

obsolete said:

Whoo boy. What's the diameter of the flapper? How about replacing it with a larger one?

I had a turbo once where the wastegate port was a little too big for the flapper. It just barely covered (couldn't see light through it) but the edge of the flapper would catch on the edge of the port sometimes, so it wouldn't always close all the way. I was able to find a flapper that was just slightly bigger, and it solved the problem.

Actually, just looked through my eBay purchase history and found it. This is the one I used: https://www.ebay.com/itm/161051084308

Thanks! I think that might work, its worth a shot. What do you think about getting a larger SS washer welded onto the wastegate door, to enlarge it that way? I remember seeing a post about it on a RX7 forum, but don't know how effective or safe that is. I just have my tuning appointment next week, and OF COURSE I screw something up right before that...its always how it happens, right?

I wouldn't suggest welding a washer to it - that would make the flap thicker, which then means the pivot is in the wrong place so the face of the flap won't be parallel with the port face when it is closed anymore.

Bigger replacement flap is the way to go.

It's going to be a boost leak, and a decently big one - will probably hurt how quickly you build boost, especially at lower RPM around your boost threshold.

I don't know if there is potential for burning the port. Small gaps of high pressure and high temperature gasses tend to have a way of becoming big gaps, like a burnt valve. Probably not a problem on the street, but maybe on track where you're in boost all the time and everything is really hot.

gearheadE30 said:

I wouldn't suggest welding a washer to it - that would make the flap thicker, which then means the pivot is in the wrong place so the face of the flap won't be parallel with the port face when it is closed anymore.

Bigger replacement flap is the way to go.

It's going to be a boost leak, and a decently big one - will probably hurt how quickly you build boost, especially at lower RPM around your boost threshold.

I don't know if there is potential for burning the port. Small gaps of high pressure and high temperature gasses tend to have a way of becoming big gaps, like a burnt valve. Probably not a problem on the street, but maybe on track where you're in boost all the time and everything is really hot.

That makes sense, thanks! I will probably go ahead and try a larger flap then, see if I can get it to seal up where I messed up.

Possibly unrelated question--whats the point in porting your wastegate?  It doesn't seem like it would be a power adder as it would only improve flow when the WG is open.  Are you currently experiencing boost creep?

In reply to rothwem :

It's fairly common for Chinese turbo's to have a really small wastegate ports.  Without porting they apparently suffer from boost creep (I just did this myself). 
 

It also isn't a very tight seal and this overporting won't cause a boost leak (that would be on the other end of the turbo).   This would just cause a slightly slower spool.

If you have access to a TIG welder I'd put a small bead around flapper where the gap is and file it flush before replacing the entire flapper.  Som 309 filler would probably work well.

Thanks guys! I ended up purchasing the turbo itself again just to use the exhaust housing, since the turbo isn't too expensive ($150). On the brightside, at least I'll have a spare CHRA and compressor housing! I took the housing to a few local places to ask about welding and they all said it would cost a few hundred dollars due to it being cast iron.