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.

Ive seen a lot of people reccomend the .86 housing over the .64. Im sure the EGT is lower with the .86 as it flows more, but you also get more lag and worse transient response from the turbo. I have seen dynos of cars that use a .64 housing and they make 400+ whp. I think for most people the .64 would be ideal unless you are tracking your car, or want all out topend power. I could see on a track how the higher flowing housing would be the one to choose for lower egt and better topend since you arent running lower rpms. For a street car I would choose the .64 but thats just me.

I spent all of this evening trying to get to the bottom of this. I've made some progress but still have some way to go.

My first step was to verify that the turbosmart actuator was responding as expected. A bit of bodgery later and I had a tyre compressor hooked up to my actuator, which wasn't ideal since I couldn't use an accurate gauge and the inbuilt one in the compressor would have to do.

<iframe width="560" height="315" src="https://www.youtube.com/embed/P9SkEYh6qKA?rel=0" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

This confirmed that the actuator is working without leaks. I measured the total travel of the WG arm pin to be 22mm and the turbosmart actuator with 1mm of preload to have 16.5mm of usable travel. Measuring the displacements at various pressures gave the following plot.
https://cimg8.ibsrv.net/gimg/www.mia...7636b8876d.png

Bearing in mind the potential measurement error with the inbuilt pressure gauge, the trend looked fairly clear (I wasn't expecting as smooth a trendline as this!). Interestingly, past 13psi, the pressure required to compress the spring appears to ramp up, suggesting that the spring could be getting near coil bound. This suggested to me that a longer spring with a lower k-factor but more preload (in terms of distance, obviously same in terms of force) to make it the same pressure may help creep at higher boost levels by letting the WG open further for a given pressure, but only if the WG could flow enough when fully open....

A bit of lockwiring later and I had this.

https://cimg3.ibsrv.net/gimg/www.mia...3e5611841e.png

Now it took until 5000rpm before ~6.5psi (seemingly the effective stiffness of my 7psi spring) was exceeded, but it still hit ~17psi at 6500rpm. This tells me what we already knew, that my wastegate can't flow enough and needs porting.

https://cimg9.ibsrv.net/gimg/www.mia...cdb26ffc1f.png
I then removed the lockwire, reattached the actuator (bypassing the solenoid) and took a measurement. Looking at the data, I was trying to work out why the MAP signal looked so noisy, turns out windowed MAP sensing was on... I disabled this for the plot below (though I realise this will make numbers incomparable, but by the time I realised, it was too late to do another lockwire run)

With the actuator hooked up, 6.5psi was reached around 3k, held to 4k then creep started at around 5psi/1000rpm to hit ~18psi at 6500rpm. This suggests that the actuator is letting the wastegate open to near the wired open position.
https://cimg3.ibsrv.net/gimg/www.mia...93236b50c5.png


It now looks like I need to port this wastegate and perhaps a longer, lower k-factor spring could help the marginal system if I could get the creep down to say 12psi.

Interestingly, the turbosmart actuator comes with 2 springs for its 14psi rating, an inner 7psi 43mm long spring and an outer 7psi 57mm long spring. The instructions say to run the inner spring only for 7psi and I thought this made sense from the smaller diameter spring having less resistance to rod misalignment, but I'm wondering if the 7psi 57mm long spring would remain linear during the whole travel and being less stiff (I think the installed lengths are similar though didn't measure or take pictures when I removed the outer spring) it might need less pressure to reach the 16.5mm endstop.

I've been looking at the FM2 downpipe pictures and I'm pretty sure a fair bit of my IWG divider is missing. I'm guessing that is a factor here too. Before I go removing the turbo, does anyone know if you can remove the turbo on an FM2 kit without having to take the first part of the exhaust with it along with that awful slip joint? I've removed it once before and it wasn't fun at all.

That does sound very good. Is it a lot better at controlling boost too? In the midrange, before the creep goes mad, it looks like each duty cycle % is around 5kPa, which will probably be difficult to tune accurate closed loop with.

Is this for boost creep reasons or more generally for my turbo? Obviously if going EWG, I'd need a new housing and would have that option, but I'd probably value throttle response over an extra 20whp extra... But then I don't know how much of an EGT limit I'd run into on track with the 0.64.

Interesting, perhaps that is the same housing as this one. Do you have any before/after pictures? Was your creep similarly bad to mine beforehand?

The 64 is really small and will require a significant wastegate flow to keep from creeping. But you know this. Boost is a measure of back pressure in the system. A significant source of back pressure in the system is the turbine housing unless the wastegate is very large.

The FM setup is designed so that the manifold, turbo, and "elbow" outlet casting go into/come out of the car as a unit, and are then further disassembled on the bench.

The four bolt flange between the elbow and the DP is a PITA to do in the car, but with an appropriate mix of extensions, u-joints, gear wrenches, etc it's more doable than trying to get the bottom nuts on the turbo-to-elbow flange.

--Ian

Something really doesnt sound right here. Can you remove a cat and run open pipe for a (loud and obnoxious) test? I have run both a 64 and an 86 IWG turbine on a gtx28, and dont see this at all.

I had a similar experience to Erat on my old setup - begi cast manifold, GT2060RS (not X) 0.64, FM elbow, FM 3" exhaust.

With the 7 PSI garrett actuator it would creep to something like 11-12PSI at redline. I opened up the area behind the wastegate 'penny', probably about 1/8" all the way round, the route of the gasses from the exhaust manifold to that area, and the way out on the FM elbow side.

It would still creep a tiny amount, maybe 1-2PSI extra at redline - nothing like as bad as it was before...

Turbos with small, restrictive internal wastegates will tend to creep when paired with a free-flowing exhaust. The nice open exhaust means that it's "easier" for the exhaust to flow through the turbine (thus delivering power to the compressor) than it is to flow through the wastegate.

To fix it you need to flip the balance of these two paths. Either make it easier to flow exhaust through the wastegate (porting, EWG, etc) or harder for it to flow through the turbine. The latter is easier, but kind of dumb.

--Ian

Do you make 18psi worth of power, are you burning 18psi worth of fuel?

This is interesting, I thought the reverse would be true, increase the flow resistance with a smaller turbine and the pressure differential across the turbine would increase, increasing the flow through the WG hole?

Is there any data available for creep on the same system but with different A/Rs?

I do think at the power I ultimately want to run on track, 0.86 would be better for that, but since street response is also very important to me, I'd like to try and make 0.64 work.

Thanks, I'll try it this way. Previously I left that joint alone and undid the exhaust at the flange to the midpipe but that was quite unwieldy. I took the slip joint off too but can't remember why that was necessary. It was hard work doing that!

There is no CAT here. Do you have any plots of the minimum pressures you could run with either of those?

Oddly a friend with the same manifold + DP, a similar 2.5” exhaust but a stock NA8 engine, can hold 7psi to redline with a 64 GT2560 which is confusing me.



At 11:1 and 17psi with WG open, my 650CC injectors at 45psi vac referenced were at 87% duty which sounds like 18psi worth of fuel to me?



Thanks for sharing your experience. If that took yours from 11-12 down to 8-9, that percentage might be enough for me. Did you find it affected your boost control duties much?
https://cimg1.ibsrv.net/gimg/www.mia...a0edac22c7.png
My boost control duties look like in the midrange that each 1% duty is worth 3-4kPa, which if that became coarser might be an issue. 2000rpm 3k pulls at 2% duty intervals shown for reference.

Ian, what sort of resolution do you see with your setup? I'm quickly coming round to the idea that it looks to be the best for what I'm after, high power on track (EGT control + 3" exhaust), good boost by TPS (ability to control to low pressure) but also good response (0.72)

Just port it like everyone else, its a 5 minute die grinder job and it's sweet then.

Dann

You'd think that by now with what 30-40 years of experience and like 10 revisions later, garrett would finally fix such a stupid issue, but here we are

That's that plan. I have the turbo off now, so a job for the weekend :)

That is annoying, especially as you can see how Borg Warner really designed the EFR WG from the off to actually work.

But now that I've got my turbo off, I can see that it isn't the turbine design from ATP that I thought it was... The housing on there has no internal divider, whereas this has one and the FM2 DP is cut to accommodate this.

I'm going to open the bend between the turbine flange and the WG port and also open up the hole, though note how off-center the flapper is! The hole is ~23mm (will take a better measurement tomorrow). I'll try and open the diameter as much as I think is safe to do, though it looks like 3mm+ should be achievable.

One other question though, based off the soot marks, the FM2 downpipe really doesn't look to line up well with the edges of the IWG. Does anyone think this is worth porting? The turbine exit looks fairly well matched, but the IWG much less so....

Look at mine before and after.

I also took a bit out of the area where the divider is. And go back to the first page and see that i took down all those bumps and ridges that create turbulence (maybe). I also did some work to the coldside and work on the log manifold.

https://cimg5.ibsrv.net/gimg/www.mia...f1e4df09f0.jpg

https://cimg1.ibsrv.net/gimg/www.mia...c14904c023.jpg

https://cimg5.ibsrv.net/gimg/www.mia...0a0fe1036a.jpg

Thank you for the pictures. It looks like your turbo matched up to your DP a lot nicer than mine!

Were you able to measure any differences with that porting? I hadn't thought of doing that much, but I will.

Seat of the pants says it spools faster. But i really have no idea.

This port job didn't last long. I was on the stock engine when i did this, It wasn't long when i went built engine and things got crazy very quickly. Every time the car went out during the "building" stages the tune was being optimized. So any gains or losses could just have been tune changes.

I know the feeling when things keep getting out of hand quickly. I'll post my findings up here (along with some pictures) as I progress. I'd be happy with it only creeping to 12psi, but any other benefits would be a good plus!

I would creep to 20psi. Don't mind the tune, i was trying to keep it somewhat a live. Fuel and timing were WAY safe.



Doesn't matter now, low boost for me is 15psi. But who needs low boost?

Yep, that looks like mine. Ultimately, 17-18psi low boost might work, but I'd like EGT feedback to be able to dial back the boost duty if things get a bit hot (especially if I go to the Autobahn and go for Vmax...) and I'd like to keep boost by TPS.

Not sure what you mean by 'resolution'?

--Ian

Here's my bias duty table. The 180, 210, and 240 rows are decently well tuned. 270 and above I haven't tuned properly (I did some quick hacks to it on the dyno, but it needs more), and 160 is below the 10 psi spring that I currently have installed.

http://www.codrus.com/miata/fm2r/bia...g-2018.mid.png

--Ian

This porting is harder work than I anticipated. These so called "Tungsten Carbide" dremel bits from Amazon seemingly only last 10 seconds each. I'd have thought a pack of 20 would at least be enough for this one job. Does anyone have any other recommendations? I only tried Amazon since I wanted it next day (to do this weekend) but looks like it literally isn't going to cut it. The UK is awful for trying to get usable tools (ie not eBay/Amazon fail specials but not full on Snap On baller glory). There's no equivalent of Harbor Freight here!

Thanks, that looks like a good amount of resolution. I know that EWG is ultimately the answer....

I'm almost positive i got my carbide burr kit form amazon and i've used the HELL out of them. Hell, i ported a couple SS manifolds with them.

Edit* it looks like this one. But my case opens a little different.

Even Amazon looks better in the US :cry:

This is the set I bought.
They're fairly effective for the first few seconds, then get less effective, then after a minute or so have turned blue from the heat!

I'll see what I can find for a drill, maybe it's more than a Dremel type tool is meant for.

Those you bought are HSS.

That title is not just misleading but wrong. You want to spend around $50-$60 for a set of 5. So what's that like 40 pounds? You also want double cut, they work better.

I have these ones for my die grinder:
And these ones for my dremel:
Both of them work quite well.

--Ian

Ill trade you for my gt2560, I used to have creep and I ported the shit out of it over the winter. Now I hit 16psi and taper down to 14.5 by redline. I have a 7psi wastegate spring and I ordered a 14psi can so my problem should be fixed, but the port work makes all the difference. I dont have pictures of exactly how I ported it, but start at the turbine inlet, and port a channel all the way to the wg hole, then enlarge the wg hole as well. Dont take out too much material make sure the wg poppet still seals.

TL,DR, issue fixed, went from ~18psi @ 6.5k to ~6psi.

Thanks for everyone's help regarding the tools. I ported quite a lot out of the housing (and a bit out of the DP) and now I measured 6.2psi @ 6500rpm (down from ~18psi before) with the WG wired open, and 9.9psi @ 6500rpm with the can connected. I guess the WG has to crack open fairly far to get significant flow at high speed (7mm from my data earlier...)

https://cimg6.ibsrv.net/gimg/www.mia...a3d700cef9.png


https://cimg5.ibsrv.net/gimg/www.mia...1e1b2b804d.png



One question I've been left with though is whether I'm getting knock here. The knock readings look like they could be saying something, but does anyone get knock at 140kPa, 20 deg spark, 12:1 fuel, 9:1 compression and 99 RON fuel?!

I managed to get some that looked similar to your die grinder ones. Wow. They were so much more effective than the originals I had bought. They left my turbine housing and DP looking like this. I took a lot out of the angle between the WG hole and the turbine inlet, though that's not easy to capture in a photograph.

Thanks you. I ported the DP to line up better with the turbine and it looks like it worked.

Thanks, I followed that technique. Looks to have worked!

.64 is more likely to have detonation than .86 due to increased backpressure. 9:1 rather than 8.6:1 is more likely to have detonation.

I'm not sure if you have detonation or a false positive on the sensor but you might pull a few degrees of timing and see if it goes away.