Sometimes, yes.

Well, I did some porting today...

Who knows if it'll work, if I've done enough, whether I need to enlarge the port itself. But here it is :

https://cimg8.ibsrv.net/gimg/www.mia...25bd8cce94.jpg

I'll be able to test it tomorrow hopefully. If all is well then I'm going to get the car booked in for a custom exhaust. I'm going to go 2.5 inch I think, that way the system is the same size the whole way through and I don't think I'll ever be wanting more than what this turbo can produce.

3" is better in every way. More spool. More topend. More fun.

Will I gain that much from going 3"? The cast elbow and downpipe from the Flyin Miata kit is 2.5".

Yes you will.

3" from your downpipe back for sure.

Does your downpipe bottle neck down to >2.5" at the end of it? If I remember correctly, my FM downpipe had that bottleneck to get it to fit with a stock cat. I'd highly recommend having a welder/exhaust shop chop that neck down off and get the downpipe to a proper 2.5" all the way.

Hmmm you know I haven't measured that point, I measured the outlet of the turbine elbow and the main pipe. Looking at it though, it looks the right size.

Seems like I should go 3" then!

That said, if my wastegate porting hasn't worked going for a 3" system is only going to make things worse?

I got the car back from the exhaust place, they have fabricated the section I needed to join the downpipe to the exhaust. The car is lovely an OEM feeling now, noise level is subtle which is nice for a change.

However, I still have boost creep, it doesn't seem as aggressive - by that I mean it creeps slower than it did.

So where do I go from here?

I'm getting a little fed up really. Given shipping costs and import duties etc this kit has cost me a fair chunk of money and I basically have a turbo that seems to be flawed by design. How I wish I'd come across this problem before I ordered!

I have several options as far as I can see:
1) Buy a different turbo that uses something like an ATP externally waste-gated turbine housing. Maybe a GTX2863R. Not a cheap way to go.
2) Take the turbine housing to a machine shop, have them weld shut the internal wastegate, then drill a hole and weld on a flange for an external wastegate much like the ATP housings.
3) Take the turbine housing and cast manifold to machine shop, weld shut the internal wastegate, machine the manifold to have an external wastegate (roughly where the "Powered by Flyin' Miata lettering is).
4) Shove a restrictor in the exhaust - not really a fix.
5) Enlarge the internal wastegate port and flap size on the current housing - doesn't look like there's a great deal of space left to widen that though.
6) Shove some forged rods in the block and turn the boost up to 18 and presumably eliminate creep - looking like the most likely - will I overcome creep at this level?

Very much welcome your thoughts on this.

-Lew

What we have found with the t3 chinacharger I use on my setups is that enlarging the wastegate hole works much better then making the channel like you did. That would be what I would look into next.

What size enlargement is required though?

I presume I could do this myself if I can purchase a larger flap and just cut away with a carbide burr again. I suppose the main thing is to ensure that there's enough metal left between the edge of the port and flap?

https://cimg4.ibsrv.net/gimg/www.mia...d78f915246.jpg

That's the best picture I have of the back, it just doesn't look like there's much room for improvement when you factor in needing a larger flap.

I don't remember what size enlargement exactly. Nigelt and sonofthehill have some pictures in my big for sale thread and in their individual build threads. Basically what you do is use a sharpie or something to draw around the stock flap, then lift it up and clear out some space less the the drawn hole. Not sure how much actual free room there is on a T25 though, as I never looked. I know when I ran my 2554 on a begi setup with 3" exhaust I did not get creep. I don't remember if Corky did any porting though when he had my turbo.

IIRC, Nigelt enlarged his port radius by 2.5mm. you should read through the thread though. The hole is typically offset as it is enlarged so that it doesn't hang up on the WG flapper. I have no idea whether your turbo would need, want, or accommodate that much enlargement.

OK so I have been chatting with a friend, and I might take the FM mani to a machining place and have this done:

https://cimg6.ibsrv.net/gimg/www.mia...3bd3eacf49.jpg

And run an external wastegate like this:

https://cimg8.ibsrv.net/gimg/www.mia...e3d0285c29.jpg

Quite frankly it's overkill and I shouldn't have to run an EXT WG on a GT2560R. I have no problem paying for an external wastegate, the idea of spending the extra money and getting this FM kit was that it should be bulletproof and I can enjoy the car rather than panicking over all the parts - I haven't got to this stage yet, and if doing this cures my boost creep which is almost certainly will with a 38mm port then I can enjoy the car.

ps. I'll also be welding the flapper shut.

Once again, I welcome your opinion/criticism.

I did have look and it seems like people have done this themselves on this forum.

-Lew

I think you may have flow issues to the wastegate, but I'll let the more experienced chime in.

I raise the same question, why not just use the internal flap?

If the internal one just worked then I'd be sticking with it. I've ported the valley leading to the wastegate itself and that made a difference, but I still creep to 12 psi and have to let off.

One last attempt this weekend (tomorrow in fact) is to widen the port itself if I can, I believe the flapper overlaps the port by about 3mm all around, so if I can widen that by 1-2 mm then maybe it'll be enough to keep it <=10psi.

I'm quite happy to run up to 12 psi eventually, but at the moment there's no stopping the bloody creep, it just continues to rise after 5000rpm or so.

I've got a spare gtx2867r with no exhaust housing if you want a bargain on an upgrade path (I saw you mentioned it). Turbine wheel has had the edge chewed a touch so I bought a new one but it spools identically. I wouldn't have bought the new one if I had known there would be no difference.

I've only gone and fixed the boost creep!!

I took to the wastegate port itself, there was a good amount of overlap so I was able to take away a good amount of metal and it still seal. It's not as neat as my valley porting but it's functional and now holds a steady 8psi all the way.

I'll post some pics tomorrow, thanks for the help guys I can finally enjoy the car and look forward to building up the next block.

-Lew

Glad that what we suggested helped.

Yes I'm very pleased with the outcome.

Just discovered I can share pictures on here directly from my phone, here's an 'in progress' picture, for some reason the later ones I took don't quite show my work right, they make it look rougher than it is. Again used a Dremel and carbide burr.

Funnily enough I shared my work on the Mx5nutz Facebook group, got absolutely laid into by a bunch of useless twerps that were telling me I was doing it wrong, that I should be restricting the exhaust and that boost creep is when too much gas escapes the port...

Then I was accused of lying about fixing my creep and shortly after posting a video as proof I was kicked out by a mod. I guess he saved me a job.

The line you can see in the photo is where I scored the carbon away as a limit I could work to.

​​​​​https://cimg3.ibsrv.net/gimg/www.mia...602eadaa80.jpg

We can be absolute assholes on here, but we also generally know our shit.