Awful popping. Can't tune it out.
 

For weeks now, we have been trying to isolate what's going on with the car. In 2nd gear, mainly, when I rev up to high rpms it will pop a ton. We've tried boost settings, fuel settings, spark settings, almost everything and nothing seems to make a difference. Tried to record a video of this popping happening.
Here is a link to it: Hopefully someone knows what the heck is going on.
Here's a link to the megasquirt tune file: https://www.dropbox.com/s/xxqd6ie8za...tTune.msq?dl=0

Spark blowout? What are your plugs gapped to.

Did you ever add more fuel like what was suggested in your last thread?

https://www.miataturbo.net/megasquir...lp-tune-92145/

Also. post a log.

Plugs are now gapped to .020.
Increased the fuel pressure thinking that would provide more fuel and then followed that up with an autotune. Should I just manually increase the fuel in the specific cells in the ve table and not rely on the autotune?

idk. post a log

I am attaching three logs. The first two are pulls where the popping (misfire?) happens when the RPM is > 4200 and fuel load is > 100%. The third log shows what happens sometimes when just cruising along. I was in 4th gear around 60mph. The AFR was steady around 15.3 and then suddenly dropped to 10.

Any help will be greatly appreciated.

if fuel supply is constant and AFR drops, it means you aren't burning something.

Don't think so. It's an oxygen sensor. So if you have un-burned oxygen in your exhaust, the AFR will go up, no matter how much un-burned fuel is also present in your exhaust.

Yep, unburned mixture will register lean

It's your TPS enrichment. This is from the "AFR goes haywire" log. AFR goes haywire, because a lot more fuel gets injected suddenly. This is caused by TPS_accel it seems. Turn that off and try again. Note: Sudden movements of the loud-pedal will likely result in lean mixture and stumbling engine after turning off TPS_accel.
https://cimg0.ibsrv.net/gimg/www.mia...be1f6b09a2.png

sorry, overworked. I remembered while typing that it felt wrong and was counterintuitive.

my bad. happy hour required.

Just returned from a tuning run and had some success. Decided to see about lowering the values in the VE table where the misfires occur and things improved. Did a few pulls and paid attention to which cells it was in when the misfires happened and lowered those cells. Eventually, all of the misfires were gone. Does this mean that the whole problem was too much fuel flooding the cylinders?

I still have the random richness when cruising along steady. The AFR gauge looks like a windshield wiper when it happens. I have the acceleration enrichment turned off at the moment. Could this be a grounding issue?

The answer to your question is in my above post. Your TPS_Accel is triggered. How did you tune it?

So far, the only place I have found anything that looks like TPS_accel is in the Acceleration Enrichment Settings and Wizard. I turned off AE so I figured that would turn off TPS_accel. Guess not.

Sorry- I missed the part where you wrote that it's turned off. Post your tune and log, so we can make sure....

I now realize I only had the ENHANCED Acceleration Enrichment turned off. I have attached my tune and a handful of logs. I do see in the logs where the sudden drop in AFR follows closely behind a bump in the TPSaccel. Please look over my tune and see if something looks totally wonky. Thanks.

It looks like your TPS isn't calibrated. It varies from 0-8%- it should go up to 100%. Bad calibration of TPS leads to random enrichment.
That's assuming you have a TPS and that "TP" in your logs shows the TPS position.

After many hours researching online and experimenting with different settings in TunerStudio, I haven't made much progress in eliminating the stuttering that occurs at high RPM and fuel load. I'm attaching my latest current tune and a log of a couple of pulls I did tonight. Please take a look. I appreciate any advice and recommendations.

I long for the day when I can go WOT without any concern.

I don't see any logs showing 100% TPS, including your last one. Did you calibrate your TPS as suggested over 3 months ago? Are you actually going WOT?

The TPS is calibrated. I'm not going WOT due to the sputtering that happens in boost. You can see the RPMs have a sawtooth pattern when it happens.

Just a pro-tip when you have TS open and are running capturing a datalog, you can hit the space bad and that will make a mark in the log file. This makes it easy to pinpoint where problems are.

Open the plug gap to .028 and see if that helps. It is possible to have the gap too small, also.

I increased to gap to .028 and there was no improvement.

So, help me understand something. Is the popping I hear likely unburnt fuel igniting in the exhaust? If so, should I advance or retard the timing in those areas in the map? I have tried minor adjusts to the timing but didn't want to go too far and risk damaging something.

Not sure how you arrived at your VE table, but a 20% fueling change from 120 to 140 kPa @ 4800RPM seems a bit radical (from post # 17 above):


https://cimg0.ibsrv.net/gimg/www.mia...fd7e9e2649.jpg

Why are you running such an old firmware revision?

The VE table is a result of Tune Analyze Live. Below 100% fuel load, the car runs quite nicely. Above, with the throttle < 70%, it runs pretty good. More throttle and the popping happens and the AFR goes very rich and then lean so Tune Analyze Live tries to add more fuel. I'm just not sure if I should not autotune above 100% and just manually set it up or if something else (like the ignition table) should be tweaked so autotune will do its thing.

I'm pretty new at this and didn't realize it was old and that there was another I could put on. I'll look into it. Thanks.

Update firmware version, as mentioned!
With a quick glance you are using enhanced accel enrichment, turn that off, lower your tpsdot adders in normal accel enrichment, then use VE analyse live properly(search).

Do you get any sync errors? How's the health of your cam angle sensor (CAS) and crank position sensor (CPS)?
Check your CPS gap.
Does playing with timing at those RPMs fix things? I had a very similar issue. Playing with timing helped...however the real issue was because of two things: my CPS gap was wonky, and my timing offset was off. Essentially the car was getting excessively advanced and combustion didn't occur correctly.

Also did you ever use a timing gun to check your timing offset? This is EXTREMELY important, I followed the stock advice that my offset was at 10? it turned out to be different in actuality. I also relocated my CPS.

I went to update my firmware and, when it asked which one I had, I wasn't 100% sure. I only knew what the previous owner told me but I wanted to double-check. The ECU housing doesn't have any label or identification of any kind so I removed the housing. Here's what I see:

https://cimg2.ibsrv.net/gimg/www.mia...f053f9fe4e.jpg

According to this site, Megasquirt Identification ? what Megasquirt do I have? - Megasquirt EFI, it must be Microsquirt. Is that right?

You have a DIYPNP which uses the microsquirt board. Firmware you want is the 'MS2/Extra 3.4.2 release Firmware' which can be found here: Megasquirt Downloads Firmware and Software - Megasquirt EFI

Ok. That's the one I downloaded and ran but wasn't sure when it asked one of the questions. I don't have it in front of me but I recall the options were something like:

1. Megasquirt 2
2. MSPNP2
3. Microsquirt
4. ???

So, "MS2" makes me think I should select "Megasquirt 2", "DIYPNP" makes me think I should select "MSPNP2", and the existence of the microsquirt board makes me think I should select "Microsquirt"...

There should be an option for 'Microsquirt Module'. That's the one. https://www.diyautotune.com/support/...ding-firmware/

Microsquirt Module as suggested.

Thanks for the clarification about the Microsquirt module. I plan to update it tonight. In the meantime, I did a few things.

1) Checked my crank position sensor. It was covered in gunk and was about 2 credit card thicknesses away from the nibs on the gear. I cleaned it and closed the gap to 1 credit card thickness. It seemed to make a minor improvement but nothing quantitative.
2) I swapped out my TPS with one from my other 97. Recalibrated it and it might be a little more steady than the old one.
3) Checked my base timing. Holy crap! It was not right at all. It was at ZERO when TunerStudio wanted it at 10. Guess that means all of my spark map was 10 degrees retarded from what TS thought it was.
4) Adjusted the base timing and made a quick test run. Significant improvement. It still misfires but not in the same areas and not quite as harsh.
5) Took a data log and noticed that the misfires primarily happen when the spark advance drops to 12 or below starting around 150kpa and 4600 rpm.
6) Increased the spark advance a little in that region and further improved things.

I'm loving the increased power! I'm excited that the car is starting to feel like I thought it should.

I'll post another update after I update the firmware. Thanks for the info, suggestions, and patience.

Oh well, seems like this needed some on site troubleshooting.
Study the forum, you can make your car run great, just by doing that.

Updated the firmware and took the car for a drive. No misfires at all. It's never driven this good!
This forum is an invaluable resource. Thanks again.

Uh, who is Kricket, and who is powelke?

Kricket is my son. He made the initial post while we were out tuning one night. He introduced me to the joy of Miatas.

that pot resistor you have in your unit, next to r20, could be part of your problem...

As I said, your ignition was probably way way off. I had the same exact issue with my DIYPNP and my RusEFI. I figured my car was just toast when both ECUs made the car run like crap. Good to hear that you got your timing offset right and the cars running great!

We have basically the same setup, I LOVE the spool on the GT2554 (my SR20 Turbo is basically a JB GT2554R). Make a build thread and show off some pics!

I really should do a build thread. Even though the car was built by someone else, I have done my share of tweaks since I got it in December. Here's a recent pic.

https://cimg8.ibsrv.net/gimg/www.mia...e0d93f9bc9.jpg