Hesitation at high RPMs/High Boost (99 / DIYPNP / Flow Force / Fab9 / 8.5:1)
 

I'm having yet more issues with my build. Although I'm probably 95%+ of the way through the project, I've never been more discouraged.

Overview:

• As the car accelerates through the RPMs,there're an intermittent flat spots/hesitations (The best way I can describe it is: someone lightly tapping the brakes for a millisecond second, randomly).
• I've played with many variables including but not limited to: Fuel, Dwell, and Spark Duration, etc. and non seem to affect the hesitation (expect ignition/boost, see below).
• The car was showing signs of this with the OEM coil pack at 17+psi, so I purchased 1 step colder plugs and the FAB9 COP kit, and now it's WORSE
  
• Ignition timing DOES affect it through: For example, when running 11 degrees at 5K RPMs, it's much WORSE than running 18 degrees at 5K RPMs.
• Boost DOES affect it: For example, when running 17psi max, it's much WORSE than running 15psi.

At this point, I'm running so much timing (since it seemed to help!), I'm worried about further testing.

Attached:
There are two WOT logs attached. The one named 2017-02-19_16.10.39 High Timing , with very little signs of the issue. The second log. 2017-02-19_16.14.09 High Timing +2lbs is the same tune, but with two additional lbs of boost. The issue was so bad, i backed out of the throttle early. Current tune also attached, b/c what the hell.


Any thoughts on the topic would be greatly appreciated.
Additionally, any recommendations on a Miata tuner familiar with Megasquirt in the NJ/PA area would also be appreciated; although everyone advocates for tuning your car yourself, I'm pretty defeated at this point.

Thanks

I had a similar problem on my 93. I switched back to the Toyota COPs from the Fab9s, that didn't really help. Then I found my fuel pump relay in the fuse box in the engine bay wasn't fully connected. That helped a bit, but there was still a slight hesitation. Finally I replaced my fuel pressure regulator and that solved my problem. I think it was a combination of all those things. I've talked to a few high boost miata guys who said the FAB9 coils caused a hesitation above 10#, but the fuel system is what I think really caused it for me.

If car doesn't lean out when this happens, its likely the ignition setup

Change the cam sensor. I had something similar going on and that's what solved it for me

Thanks for the feedback everyone.

Sirnixalot, great idea! The Cam sensor is pretty much the ONLY thing that hasn't been replaced at this point. And it's seen better days. I just placed an order for one and it should arrive by end of week. I'll report back with my findings.


Thanks again all

I didn't see plugs mentioned, although I assume you've probably swapped them already. The cheap BKR7E's everyone runs work great but don't last very long. I swap usually swap them with oil changes. A few times I've left them in too long and I'll get symptoms exactly like you describe. It's certainly worth a $10 set of plugs if you haven't done them recently.

what ECU do you run? fab9 cops didn't want to play at all with my ms3, getting worse than with the oem coil pack. This was in a wasted spark setup. Fab9 wasn't very helpful with a solution and I'm still to try and run them in sequential, so can't tell you if that fixes it.

I was running BKR7E's with the OEM Coils. Gapped at .35.

I replaced them with Denso IK24 that were included in the Fab 9 kit. I gapped them at .28 and .35 and neither solved the problem.

I run a DIYPNP with wasted spark.

I still find it odd that increasing ign timing helps the problem while boost makes it worse :-/

If you suspect the ignition is not up to par perhaps try temporarily closing down the plug gap? If it works better at the same boost you have your problem.
It might not idle as well...so ignore that if it happens.
Hope that works for you!

Jamie

Edit: Boost might be blowing out your spark.....I have no idea how good that fab9 system is so take it for what it is worth

My theory: Car develops light misfire in boost. That's typically ignition breakup. More timing will help because you're lighting off the plugs with less cylinder pressure. More boost makes it worse, obviously. You added a kit which is well documented to not play nice with your ECU and the problem got worse. No surprise there.

Go to a D585 setup. I bet it fixes everything.

Update!

1. I replaced the cam angle sensor
2. Continued to adjust fuel/timing

Results: Problem remains.

New findings:

1. Initially I thought I had the car fixed (after changing the cam angle sensor) until I took it for a longer drive:
   • The car progressively gets worse the more pulls
   • The first pull is the best (cleanest/most powerful/smoothest) Each subsequent pull gets worse (the car is now fully breaking up under higher RPMs/load)
2. After a lot of reading I assumed the my Ignition Module was over heating. I pulled over and it was BARELY even warm to the touch (both sides). So do not think that is the case.
3. But! the coils themselves were VERY hot (although I don't know how hot a coil is supposed to be sitting a few inches from the head of the motor??)
   • At this point i assumed my Dwell settings were off and causing the coils to overheat.
   • Unfortunately, i have them set to 2.6(ms) Nominal Dwell. (fwiw, spark duration is 1.5ms), so that is likely NOT the case.
4. I went back my logs and noticed MegaLogView said Dwell was actually 2.26
   • I then reviewed my Dwell Battery Correction settings which show a %age to voltage of: 128%@12V, 102%@14V, and 88%@16V
5. I then noticed my MegaLogView was reading 17+V at all times(thus why my Dwelll is getting pulled under the 2.6(ms) it's set to.
6. I figured: YES! Maybe my Alternator is failing and sending too much Voltage. I can replace it and we're finally good to go!!!
   • Unfortunately,I put a multimeter on it this morning and it's putting out 14.9x V's

Current Status/TLDR:

• Car is breaking up at high load/RPM but GETS WORSE the more pulls
• Fab 9 coils are VERY hot to the touch. Ignition Module is cool. (Dwell setting are low)
• Alternator says 15V, but the DIYPNP logs in MegaLogView say 17V+

Thoughts?

Why are you running an ignition module? That was only needed with stock ECM's where you couldn't control dwell. That module is most likely altering the dwell you're sending to the coils. On top of that those fab 9 coils have been known to be junk. I'd yank the whole thing sell it and make your own with Toyota coils and eBay connectors wired directly to your ECM, if you have enough spare outputs you could even do sequential ignition.

Looks like your alternator control isnt setup correctly which is what's causing the high voltage. Make sure you have it setup for field control, and wired correctly ECT.

This^^^^^

Sell the Fab9 setup to somebody else with a lower power setup

1. Hmmm, I'm under the impression the included ignition module should always be used? Do happen to have details/documentation showing otherwise?

2. Do I regret getting the Fab 9 setup? So far, yes. I've had a lot of headaches with it. But right now I'm not convinced it's the root of my problems.

3. I don't think "Alternator Control" exists for Reverant built DIYPNP? But i may be wrong. Are you thinking of the "Calibrate Battery Voltage" setting in TunerStudio?

Thanks!

FWIW I've had the FAB9 setup on my car for over 2yrs. 1.5yr before I put the turbo on and 1 with the turbo. I run 15PSI boost and have never had a problem since I changed to the "upgraded" module which he sent me no charge (problem surfaced before I went turbo).

Car's in storage but I can chance my setting in Tunerstudio if you want. I use an MS2 FWIW.

Not saying they aren't the problem

Thanks bahurd. If you can send the tune over, I'll certainly take a look!


I've given it more thought and I'm wondering if my: LOW dwell setting (2.26 as a result of my DIYPNP misreading voltage) is causing the misfire, which is heating up the coils.

https://www.miataturbo.net/useful-sa...writeup-12704/

Specifically look at the wiring diagram, coils connect to factory harness.

You can keep running in circles all you want it's kinda entertaining.

What is your current plug gap?

I just bothered to go look at the fab 9 COP setup and they use a coil without an ignitor so I was wrong in that they don't need it, sorry about that.

I still stand by the fact the ignition system is the root of your problem, start at the spark plugs and work your way up the system.

.035"

I'm wondering if problem would vary so much as the car warms, if it were do to something as static as plug gap? But I'm open to suggestions.

Update:
I Increased Dwell by 30% and decreased Spark Duration by 33% to align with a known-to-work tune. I'll report back once I drive the car again. Thanks again everyone.