Trouble with Triggers
 

I'm getting trigger errors once the car has been running on track for 15 minutes or so.

Car/Engine:
- 99 NB1 with an ancient FMII setup
- Stock cam and crank sensors
- Stock damper and cam
- MS3X with the pots set up as per Westfield's instructions

Issue:
After running on the track for a while I get trigger error 31 and 32, but mainly 31. The car becomes pretty much underivable. I had observed this once before September last year, and again today. It only happens on track and only after the car has been running hard for a while. Temperatures are OK. See pic:
https://cimg2.ibsrv.net/gimg/www.mia...c65d81d625.png
My problem is that I can't reproduce it in a static setting and taking a composite log on a track is tricky. The crank sensor was replaced about two years ago.

I see three possible causes:
- Crank sensor FUd
- Cam sensor FUs
- Pot settings in MS3 wrong

Any suggestions on how to proceed with troubleshooting? I'm planning on setting the fans to ridiculously hogh temps, to try and reproduce the issue, if it's caused by heat. But what if it isn't?

Log and tune attached....

I read this thread recently after following the rabbit hole on leafy's thread recently. I had this issue on the stock ecu last year.

The first post sounds eerily similar to yours : https://www.miataturbo.net/ecus-tuni...failure-74009/

This was posted on his thread as well: http://mazdaracers.com/topic/5310-ca...or-issues-fix/

I would check crank sensor spacing to the wheel. With a nub at the sensor, set it 2 business cards thick away from the wheel. In my experience, that works better. If that don't fix it, I bet it's the input circuit on the MS causing the issue.

Yupp- that sounds exactly like what's happening. I'll see if heatsoaking in idle can reproduce the problem, if so troubleshooting with a scope and MS3 shall commence. If not, I'll probably just convert to rusefi which uses a proper MAX9924 decoder - and I have a board sitting on my desk already. If that doesn't help, start swapping sensors. I just hope I can reproduce the issue without having to drive to a trackday after installing new sensors, just to find out "well, that wasn't it"
Pat: When I installed the crank sensor I went with one old style credit card (the new ones are too think to set crank sensors), I would have thought that having the sensor further away would make it worse, but I'll try.

You don't have to buy a new sensor even. Just modify the one you have. It'll take less than an hour. IMO, feeding a proper decoder with a fuzzy signal will still likely produce the same results.

What is this mod you speak of?

The one linked in the post by RTC. In the Spec Miata Cam Sensor Issues/fix

Yup, there are links to the parts on there. I want to do this soon because I've dealt with the issue before and it almost ruined a road trip with my girlfriend. I can see it happening more often now with the extra heat from FI.

I'm curious if anyone has had any luck heat shielding the sensor, but it seems like a waste to reinvent the wheel of the SM fix works well.

That's the fix I was referring to on FB messenger where the 'square waves get all janky' and the mod helps fix. I'd try that before swapping ecus. Can always order a spare for the track in case it doesn't work, but in not sure that would last more than 20 mins on track.

Did you need an excuse to add hood vents? This might be a good one haha.


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Duh!
Thanks guys. It was not a link to MT.net, so I immediately dismissed it....
Now, after I read it, this seems to make sense, even though it's a bit surprising that OEMs would use something that can fail so easily in such a crucial application! So it's likely just a bad connector. Well, that would be the cheap fix of the month for me.

So, the sensors seem fine:
https://cimg5.ibsrv.net/gimg/www.mia...e39935d98d.png
CMP and CKP signals look both as expected. No missing teeth. No double-teeth.
It appears that MS is getting confused by my triggers. This presumably means that my trigger phasing is off. Possible causes:
- Intake cam off by one tooth (I *really* don't think so. I checked and checked again many, many times and it was correct, but I've been wrong once before)
- Is it possible that it's the old "slipping harmonic balancer"? I don't know if the trigger teeth are connected to the crank (which seems to be the way to do it), or if they're maybe connected to the outer ring which could slip
- Timing belt is very slack-y
- My triggers are set up wrong (falling/rising edge?)
- MS trigger recognition code is buggy and running on the ragged edge

Any ideas? Does anybody else have a trigger log from an NB1 you could post to compare?

Also: This problem is a total pain to re-create. I ran my engine up to almost 250F until the coolant overflow started to bubble- nothing. then, after running around 240F for a few minutes I got it. But it went away before I could get the trigger log re-started. Let the engine cool down and went for lunch. Let the engine run up to temp again for half an hour or so- nothing. Turned on the fans to cool it down and all the sudden around 200F it started happening. And then it happened again on the way home with engine at normal operating temp. Any input would be seriously welcome...

So, it's definitely phasing.
https://cimg2.ibsrv.net/gimg/www.mia...14549ba4e7.png
When the crank trigger comes soon after the single-peak cam trigger, everything is A-OK. If it comes even a tiny little bit before, I get the error.

Now what is causing this?

Go into Tunerstudio. Click "Ignition Settings", select "Ignition Options/Wheel Decoder", where you see "Ignition Input Capture" change that from Rising Edge to FALLING EDGE. Fixed.

Makes sense- I'll try that tomorrow. Fingers crossed.
What's killing me though is that the last time I took a composite log before that, the distance between the cam and crank signals was much larger- see image below. I'm 99% certain that I never ran "falling edge" and I'm just as certain that the log in the image was taken a few months after I did the last timing belt.
So what could have changed between the image in this post and now?
https://cimg2.ibsrv.net/gimg/www.mia...df8a0c9e76.png

I have had strange results with the composite logger showing "bad data" sometimes. You'll start a log, it will show nothing for a while, then when it does show something sometimes it's off at first, but then it's right. Weird behavior, and to be honest that was prob 2 years ago last time I used it. So I can't say for sure what it's like now.

My guess is you had it at falling edge before. Last image you posted looks right.

Thanks Pat!

I changed over to falling edge. Comp log looks better now. I can't reproduce the issue sitting idling in the DW, so I hope that's it. Next track day is Tuesday- we'll know then :bigtu:

Base timing may need to be re-set.

Did that right away. Was about 1-2deg off. Fortunately it was off in the safe direction, so I wouldn't have blown up the engine without resetting it.

And now that I'm writing this, I'm wondering: I was triggering on rising edge (which presumably comes before falling edge) and now I'm triggering on falling edge, the trigger should be later, so the timing should have been more advanced. Right? I did verify with a timing light, so I'm fairly certain I got it right, but still- where am I wrong?

Falling edge comes first. Line is at 5V, when tooth comes by, the line drops low, stays low for about 1ms, then jumps back to 5V.

Glad to see that fixed it!

Yupp. I remember- I scoped the signals a while back for rusefi VVT and PAT got it right. Once the rpm is above ~300rpm or so, the signal inverts and looks like this:
http://rusefi.com/forum/download/file.php?id=2293

What car year model and sensors was this inverting-above-300-rpm behavior seen on? I have not seen that behavior, although I haven't looked for it either.