EFR 6758: Where the heck is my spool? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-04-2017, 04:29 AM   #1  
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Default EFR 6758: Where the heck is my spool?

Looking at all those marvelous spool data from other members I wonder where my magic unicorn EFR spool ist hiding. I'm only hitting 200 kpa at 3,800 RPM. It really feels like an old-school turbo ("nothing.....nothing...still nothing... BANG").

I'm running a VVT engine, MS3-Pro, 750cc EV14s, Walbro 190HP. Full 3" exhaust system, 2.5" intercooler piping. Exhaust manifold is a welded log manifold; intake manifold is a squaretop mani.

If I do a pull in 4th or 5th gear from 2,000 RPM boost is only slowly building. At first I thought I was given the wrong EFR 6758 A/R housing (0.85 instead of 0.64), but when I installed an EFR 6258 (0.64) the spool was identical :( Some KPA data from the pulls:

RPM 6758 6258
2500 112 110
3000 130 131
3500 160 164
4000 227 235
4150 250 250

Even my tuner says I should hit 200 kpa at 3,000 (as others with a similar setup do). Things I tried:
- switching between external and internal BOV - no effect
- running with the wastegate signal line unhooked and wastegate wired shut - no effect
- 100% EBC duty cycle - no effect

I'll temporarily bridge the intercooler next, and run a pipe directly from the compressor outlet to the intake manifold to see whether my intercooler is holding me back. Beside that I have no idea what else to do. I could check for boost leaks, but I'm certain I don't have any leaks. Oddly enough when driving on the highway and touching the throttle beyond 4,000 RPM boost builds INSTANTLY. So there is no boost lag at higher RPMs. But down low it just takes forever to spool and build significant boost.

Is my log manifold holding me back? Or am I expecting too much from the EFR turbo?
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Old 07-04-2017, 10:49 AM   #2  
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Can you please post tune and logs from your pulls?
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Old 07-04-2017, 11:58 AM   #3  
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wastegate might be stuck and not fully closing. had this happen on several of the efr's
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Old 07-04-2017, 12:39 PM   #4  
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pics of your manifold? logs aren't the best but normally spool up alright.

any exhaust leaks? post turbo leaks slow exhaust down too.
Being that the change from a 6758 to a 6258 didn't change anything its safe to say its a supporting mod of some kind limiting performance.
Do you have a cat converter?
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Old 07-04-2017, 12:50 PM   #5  
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Quote:
Originally Posted by 18psi View Post
wastegate might be stuck and not fully closing. had this happen on several of the efr's
i checked the flapper, mechanically it completely engages (shuts). I even did a run where i strapped a wire to the wastegate door to hold it shut. Also, it's probably unlikely that both wastegates on both EFRs were stuck. FWIW, both WG actuators had their rods checked for non-binding as well.

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pics of your manifold? logs aren't the best but normally spool up alright.

any exhaust leaks? post turbo leaks slow exhaust down too.
Being that the change from a 6758 to a 6258 didn't change anything its safe to say its a supporting mod of some kind limiting performance.
Do you have a cat converter?

it pretty much looks like an Artech manifold. I have a full 3" exhaust system with V-bands (turbo - DP, DP - midpipe, midpipe - exhaust tip) and a 200cpi metal cat. No exhaust leaks (I tried to hold it shut with a rag while the engine was running.
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Old 07-04-2017, 12:53 PM   #6  
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You'll need to post logs at least since clearly you already ruled out all the obvious stuff
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Old 07-04-2017, 12:57 PM   #7  
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yeah, having just went through your build thread and the stuff here it sounds like a tune issue.

Post a log and your tune so someone can read it. (I don't do MS, sorry)

How much time did you spend tuning the VVT table? 3000rpm sounds like a point that VVT angle changes in most tunes.
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Old 07-04-2017, 01:10 PM   #8  
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yeah will do when I leave work. Thanks a lot in the meantime
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Old 07-04-2017, 01:13 PM   #9  
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Idk I think it is your EBC settings / EBC related.
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Old 07-04-2017, 01:27 PM   #10  
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except the part where he clearly WIRED THE WASTEGATE SHUT
so it should boost insanely fast
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Old 07-04-2017, 01:29 PM   #11  
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That's what I mean, like has it on inverted? So he would be holding it open?


Just guessing. Need the tune to do anything useful and 18psi would know better than me.
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Old 07-04-2017, 02:31 PM   #12  
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No he physically wired it shut. Not ebc. As in held it shut with wire.

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That's what I mean, like has it on inverted? So he would be holding it open?


Just guessing. Need the tune to do anything useful and 18psi would know better than me.
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Old 07-04-2017, 04:00 PM   #13  
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yep, that's right I removed the wastegate actuator and tied the wastegate flapper shut with a wire.

anyway, here's my tune and a log from when I ran several pulls with the wastegate signal line unhooked. This gives maximum spool (verified by having the same spool-up with the wastegate hardwired shut). Temps were high (around 30-35 C). With cooler ambient temps spool comes on a bit earlier.


Attached Files
File Type: msq VVT_EFR_6758_slow_spool.msq (298.8 KB, 52 views)
File Type: msl 6758_wastegate unhooked.msl (4.31 MB, 50 views)
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Old 07-04-2017, 04:02 PM   #14  
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for some reason my VE table is funky @ 40 kpa & 5000 RPM, i know. And for some other reason the VE numbers doen't increase with boost
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Old 07-04-2017, 04:23 PM   #15  
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If you have an intake pressure referenced fuel system, your VE numbers will stay fairly flat with boost. only absolute pressure system (as in NBs in the US for example) will have VE increase with MAP.
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Old 07-04-2017, 04:29 PM   #16  
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My guess would be a huge boost or exhaust leak somewhere.
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Old 07-04-2017, 06:15 PM   #17  
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Sounds like a boost leak. (Turbo is pushing the air it normally would, but its being lost through the leak).
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Old 07-04-2017, 08:50 PM   #18  
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is the exhaust housing properly tightened down to the chra
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Old 07-05-2017, 01:26 AM   #19  
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Yes, no exhaust leaks anywhere (verified by holding the exhaust closed with a rag; also there is no black carbon build-up at the V-bands). I'll build something to test for intercooler leaks, but I doubt that's the case.
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Old 07-05-2017, 01:35 AM   #20  
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housing being loose may not leak, but if the turbine is even 1mm off or not seated it could result in terrible spool
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