The even easier fix is to port the housing at the same time you install a catless downpipe.

The turbo isn't magic and unicorn farts, but will still do enough power to bend a few rods.

Swapping turbos is the more complicated, involved, and costly option.

That would require removing the o2 housing and the exhaust housing of the turbo. Basically removing the whole turbo. I don't wanna.

It's like... an extra hour of work more than the downpipe.

Just crank the boost up until it stops creeping. That is the MT way

It looks far shittier than an hour, and when I take that off I will break the oil drain pipe, then realize that I want to replace the manifold gasket again because it leaks when the car is cold, etc, etc and when I am done the car will have been sitting again for 2 weeks while waiting for parts and my credit card will be maxed out again.

Again!


FWIW, the downpipe only took like 5 minutes for me to remove when we did the clutch.

The key to not breaking the oil drain pipe is to remove it first. :bowrofl: It can be removed quickly with the right combination of extensions and wobbles.

I'd bet that the exhaust leak is one end of the o2 housing. I replaced the manifold gaskets with no change to the noise.

<----- Was making a joke that putting an actual feline in your exhaust system would be cruel and grounds for being drawn and quartered.

Bad WG flow needs to be addressed, this goes without saying... but running a cat as a restrictor is like any other bandaid. Porting the WG yourself is some effort, but virtually free.

Keith

If you're going to take it apart and weld, don't waste your time and ours by using a 2.5" cat. Get a 3" metal cat from whoever has them cheap.

And get a real wastegate. The turbo is not the problem.

https://www.miataturbo.net/attachmen...ine=1398817507

Why would I install a 3" cat on a 2.5" pipe?

On the wastegate subject, I am not going to weld an external gate onto the stock manifold. Wouldn't last anyway.

As you know, boost creep is a significant problem with the IHI. The SGDP makes is worse and a catless SGDP into a 3" exhaust makes it almost unmanageable. I creep to about 13psi with my setup which is fine because I have big boy rods and my target it ~15. To achieve that modest level of control took a crap-ton of work.

I ported the wastegate and then ported it some more. Once you are done, hog it out more... :vash2: The next step was to install the 17th valve. The BP exhaust valve is a few MM bigger than the stock IHI wastegate flapper. Cut the stem down and run a die over it to make some threads (don't recall the size). Install it with a nut being sure it is able to spin freely. When you are happy with how it seats, hit it with Mr. Sparky (MIG) so the nut doesn't go flying out the tailpipe at 1,000,000mph and kill someone like a 007 red-hot countermeasure.

Once you have that done, source a wastegate actuator that has a longer throw than the stock IHI. Before you take the old arm off, mock up the turbo/DP combination and hit the wastegate with 10 psi of something. You'll be shocked that it barely cracks open under full travel. The new wastegate can should push things open all the way to the back wall of the dump pipe. This is also a bit of a restriction by itself but it is better than having the flapper crack open a few mm and expecting it to control anything. You will need to fabricate some brackets and lengthen the rod too. Sorry... :fael:

This was all several years ago so I apologize for not having a part number on the wastegate actuator. IIRC, Keith @ FM found it for us. I'm 99% certain the upgraded IHI (Blousch) would creep if you blasted it against the firewall without any downpipe. It simply needs some restriction/back pressure to control itself which the SGDP doesn't provide but the turbokitty does.

BTW, the drainpipe cracks because people think it is designed to bend like the flexystraw in your chocolate milk. It doesn't, so come up with a way to pull the turbo without bending it or learn to cope with buying the ~$80 part from Mazda over and over. There's a thread on all of this on the mazda-speed site if anyone wants to take the journey. Be polite. We don't use bad words or nuke newbies for asking stooooopid questions over there but we occasionally have good tech threads related to the MSM... :party:

Defeating Boost Creep On An Upgraded IHI and BEGI SGDP

less restriction; the cat is the most restrictive part of the exhaust.

even with a 2.5" exhaust, stepping it up to a 3" cat, and even back down to a 2.5" catback, makes a hell of a lot of sense.

so buy my 3" 200 cell metal core cat in the FS section and make it happen.

What brain said.

Actually I was really suggesting you just go to a full 3 inch system. That was probably my favorite mod on my car. Quiet, throaty, not restrictive.

The drain is really not a problem. Yeah, i broke it when i did the head-to-manifold gasket because i thought it would bend.

Was pretty damn easy to replace without removing anything else. You don't want to break it when you remove the turbo? Just remove it first. Done. Saves $80 and much cursing.