Serious boost creep with FM2 GTX2860
 

Hi All,

I posted a while ago about having high EGTs with my GTX2860 FM2 setup

Forged VVT with 9:1 84mm CPs
FM2 Manifold + 2.5" FM downpipe with 2.5" exhaust, no CAT
GTX2860 Gen 1, 0.64 A/R, internal gate
MS Labs MS3 with 4 port MAC and dual port turbosmart actuator with 7psi spring.

In trying to sort my high EGTs, I thought a first sensible step was to change my boost control so I could run less boost and have better control for mapping, hence the change to the 4 port MAC and dual port 7psi actuator (vs 3 port and 12psi garrett actuator).

While this appears to have had the desired effect to 4000rpm, from there onwards it appears to creep ~5psi every 1000 rpm linearly such that I'm at 230kPa at 6500rpm. Has anyone else seen boost creep this bad with a GTX2860? I still have high EGTs, perhaps this contributes? Perhaps related, this setup appears to spool suspiciously well from low speed, with a 4th gear pull (6 speed, 3.6 diff) hitting 200kPa around 3000rpm with a closed EBC valve.

My next step is to remove the EBC solenoid from the equation and plumb directly, but it's too late here to do that now.

Is this the kind of internal gate performance I should expect? I've attached a picture of a 3rd gear pull with 0% WG duty (which looks to be correct based on how long 7psi is held after spool).

@boileralum found it necessary to port his 2860 (not GTX) wga flapper opening. Damn thing made 18-20psi with the flapper tied open. You might be seeing the same sort of thing.

Thanks for the info, this does sound similar. It was probably the exact same turbine housing if it's a T25 0.64. Do you know if porting it helped it much?

I don't think it's seen much if any run time since then, unfortunately. And yes it was same housing. His downpipe/exhaust was likely more free-flowing than yours, though. I find the sort of creep you're getting a little weird assuming everything is working properly. That exhaust elbow housing thingy on the FM setup doesn't flow awesome.

Try this: Wire the flapper open and make a long 4th gear pull and see what happens. If it still creeps, there's your definitive answer.

I wasn't making 20psi with it wired open. But almost 10... This is on a 2560 though.

https://cimg5.ibsrv.net/gimg/www.mia...45e6b692bb.jpg

Also, make sure you have overboost protection on.

It feels like you're hitting a brick wall when it turns on, but it will save your engine when you're not watching closely.

Yes, It seems odd to me too. The FM setup doesn't look great for flow.

One thing with this though, the turbosmart actuator doesn't look like it opens as far as the flapper is able to. Guess that means my testing should be
Test 1. Wire flapper fully open and test.
Test 2. Pressurise actuator and measure how far it opens, then wire flapper that far open and test again.

That looks good. How much did that help? I will keep overboost on, was the first thing I checked before taking it out with the new actuator setup.

Thank you for the info. What kind of rpms did it creep to 18psi at? For me it is 6200rpm. Do you have any pictures of what you did? Please let me know if your porting solves it once you've tested it.

Do you mean I should try that housing? I think that's the part I've already got.

Completely eliminated it.

Used the opportunity to port the rest of the hot side.

Thanks. What did it reduce it from and to? I'm wondering if there's really much I can do with 230kPa at 6500rpm since it would need to be a fairly aggressive port to get to say 180kPa at 6500rpm.

I was hitting about 9psi at 7000rpm. I can't say with positive data but i know it wasn't making much more than 1 or 2 psi at almost 8000rpm after being ported.

What you see in my picture is extremely aggressive. There wasn't much material left in that area to take away.

Thank you for the info. I'll carry out my diagnostic tests then perhaps this (though less extreme) is my next step.

IMHO, the best solution is the EWG turbine housing from ATP. This is a GTX2863, but the turbine side is the same.

http://www.codrus.com/miata/fm2r/turbo-plumbing-3.jpg


--Ian

The combination of these two comments makes me ask, are you running non-stock cams and/or are the cams timed correctly?

That does look like it should flow a lot more. What is the least boost you can run with that setup? If going with that though, would delay my project even more than it already is. (I'd originally booked a February trackday to shake this car down at!)

Stock cams. I've not verified the cam timing, though I need to take the cams out for the valve springs (which I may install sooner rather than later with my worry of this high boost causing valve float!)

Pic of 6th gear pull for reference.

Lowest I've ever tried is 7 psi, and it made 7 psi flat to redline.

Once you've used an EWG you'll never want to go back to an internal gate.

--Ian

Ditch the .64 for a .86.

I was getting really bad creep on my 2560 .64 housing before I ported it. I opened up the wg hole, and ported a channel to the wg to help the exhaust to find its way out a little easier. Now I can run as low as 10psi, it still wont really go lower than that but I was getting uncontrolled creep previously past 5000rpm. As for your high EGT readings I think Ken is onto the right path. Something tells me the cam timing must be off, maybe that is also why it is spooling so fast as well.