Lets Discuss my Boost Creep.
 

I finally have my car running again after a few years in the garage with lots of changes. Ive now getting terrible boost creep on WOT, particularly in 4th and 5th. Overboost protection on the MS cuts it before it gets beyond 15 psi or so. (forgot what its set to, and im away from the car). With EBC disconnected it still overboosts. Wastegate spring is 8psi.

The set up
1.6l
SS tubular greddy Manifold (fml)
TD05-16g Turbo
34mm Greddy (Sigh) Type S External Wastegate. 8psi spring (Externally dumped)
3" Exhaust with only a free flowing Resonator
MS3x
Blitz EBC

Most of the threads on this subject are from people with IWG and the solution is typically to Port the exhaust housing or run EWG. My EBC source is "B" in FAQ post. With it disconnected from WG, still getting overboost. Never had the issue before the 3" exhaust was installed.


Short and sweet

Should I run a restrictor/get smaller exhaust, should I change out my 34mm wastegate for a larger one(I have a brand new 46mm in my storage unit), or should I do something else thats probably obvious and I havent thought of.

Jumping off a tall building or ledge for wasting my time with the 1.6 and a bad turbo kit is already on my to-do list.

Thanks.

Aside from pointing out the obvious fails that you already know about, I'll just say that I've never seen an EWG boost creep. Ever. 34mm is more than enough to bleed off exhaust exhaust pressure to the turbo. Either the gate is not working right, or something else is up. And I don't mean port being too small

WG porting is a GT2560R issue. I find that adding a restrictor plate will not only greatly degrade your boost threshold and throttle response, it will also not fix the boost creep problem.

Check to make sure you didn't jack up your EWG dump, and that it isn't kinked or otherwise restricted.

how much does your 8psi spring overboost?

do you have a boost log you can post? (screenshot)


are you sure you hooked it up correctly? disconnecting the line SHOULD result in overboost. You need pressure on the lower port to push up on the diaphragm and open to normal levels, iirc. without it, it should go above the rated spring pressure since only the exhaust is pushing against the plunger and it won't overpower the spring.


my bet is you don't have the thing hooked up correctly.

should have full pressure to lower port.

should get no pressure to upper when solenoid is non-active. (this way if the solenoid fails, you fail to wastegate pressure).

when active at 100% DC, it should bleed all the air to the third port out to atmosphere. (at 100% DC you should be at wastegate boost levels, since no boost should be present on the top but 8psi should be present on the bottom).

any DC below 100% should raise the boost levels. (since you're adding boost to the top of the diaphragm and lower needs more before the plunger will move up and open the exhaust flow)

I will try and get a log of it doing overboosting today. Its only happening on WOT. If I slowly accelerate then it will hold 8ish psi to redline. So the wastegate seems to be at least partially working.


Heres a shot of the dump coming off of the wastegate. Nothing to kink here.
https://www.miataturbo.net/attachmen...ine=1388511886

Heres an old picture of the manifold to give you an idea of how poorly it is designed.
https://www.miataturbo.net/attachmen...ine=1388511886


Assuming the 34mm should be more then adequate with the 3" exhaust, and assuming Its hooked up correctly (ill double check today), I figure its probably one of three things.

1. Wastegate is a piece of shit and sticking.
2. EBC solenoid is failing somehow
3. Vac lines going to WG are collapsed inside.

The vac line going to the lower port of the WG is a braided line with a heat wrap on it. I did this because silicone ones kept melting. Perhaps the lining of the braided line melted? Unlikely but possible.

Adding a restriction is not something I would like to do. Just wanted to explore all options.

Is the wastegate tapped only into the #3 runner? If so maybe that's not enough exhaust being bypassed when it opens (since you'd be getting 99% of 1, 2, and 4).

What. The. Fuck. Is. That. Wastegate. Setup.



This would be the least of my worries. My DD only taps into #1 for the EWG and is rock solid under all scenarios. But the wastegate is also, you know... welded directly to the manifold.

I think you hit the nail on the head here. Assuming everything is hooked up correctly of course, if you are having creep issues it's not because the EWG is coming off only one port (not the best design, but has worked time and time again), but I think the length, size, and multiple bends of that pipe leading to the wastegate is the issue.

You are supposed to have the EWG itself mounted basically immediately off the runners, THEN you can run a long pipe to exhaust those gases somewhere under the car, or run them back into the exhaust, or whatever.

Ok I changed my mind. That is the most utterly retarded ewg setup I've ever seen and its quite obvious why it doesn't work properly.
Was the person that put that together on drugs?
Wow.

That wastegate setup is horrific.

Yes it is retarded. I think the saddest thought is that the PO probably paid out the ass for it purely because its greddy. :facepalm. It just blends into the collector with the rest of the runners facing the wrong direction. What's worse is they designed it with no bracing or gussets. The heavy ass outdated EWG would act like a tuning fork and crack the entire runner assy into pieces. I had to add all the square pieces on it and bracket it to the tranny.

It wouldn't be a terrible manifold if it were not made for an EWG. Unlike all the other greddy log guys, it has yet to crack anywhere but the WG runner. But of course it uses their retarded flange so no off the shelf turbo will bolt up.

It will all be getting replaced in the spring when I finally ditch the 1.6. Didn't see the point in throwing any more money at it until then. Hell some club roadster JDM fanboy will hopefully fund an Abe manifold for the new motor when I sell it. :D

In the meantime, I'll pull the waste gate apart and see what condition the internals are in, as well as re plumb all the vac lines. It worked he last 30,000 miles or so before the 3" and MS3. Painfully slow, underpowered miles of course.

Sure, lets discuss your boost, but don't call me "creep"

Your boost is probably as perplexed as I am by that wastegate setup, which makes my head hurt. Not only does it look like something that was fabricated using only tubing available in those bins at VatoZone, but it clearly is not working. Job 1 is to replace that hot side hot mess and go from there. I suspect Job 2, the boost issue, will take care of itself in the process.

Making one of these things work correctly is a challenge normally, even more when you have to undo stuff that PO's have done as well. Might be able to save it by hacking off the pipe and welding a WG flange to the hole, with a little screamer pipe to keep it simple, but if the WG setup is that much of a clusterfuck I'm not feeling great about the rest of it. Good luck, keep us posted.