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The MS3 Basic doesn't come with VR Pots, it only has Opto-Isolators which are used to filter the incoming cam/crank signals. Only adjustment I have is the noise filtering settings.
My current guess is that my adjustable timing plate being turned several degrees from the OEM one is causing the crank tabs to overlap the cam signal when the VVT kicks in, either that or the material isn't as good as the OEM timing plate for being consistently picked up by the crank sensor. Should be swapping the plates out and re-timing everything tomorrow afternoon if nothing changes. Most of the forum posts I can find with sync loss w/ a MS3 basic resolve this via noise filtering settings, or changing their crank wheel to a 36-2 setup. If swapping to the OEM 4 tab wheel doesn't do it I will probably pick up a FM 36-2 timing wheel and get it running with that.
Ian had an electrical hardware guy put a filter cap across his crank signal input.
Mine was fixed with FW filters as you suggest. I never had problems until I shortened by harness to take out the back to front to back engine wiring.
I have not noticed an advantage to running the 36-2 vs stock. Possibly something is improved, but I have not noticed anything. It did not fix what I wanted it to, which was a strange shelving of RPM at 700 - 1000 at start-up... then it goes on up to the desired 2000 RPM flare.
So, I think you are wise to put an OEM back in as a first approach.
I saw the filter cap fix Ian went with, trying to avoid modifying the ECU unless switching back to an OEM timing plate doesn't do it. I have a pretty good feeling about the OEM plate swap, any issue I have had with Rev's stuff is always caused by something atypical I left in place or messed with during the install.
As for the RPM shelving issue you mention, I assume you mean the car starting, the RPM jumping to the IAC Duty% in the Cranking table, then immediately dropping to ~700RPM and shooting back up to the Cranking Duty % again issue? I also have that behavior - good to know a 36-2 plate didn't work to fix that weird behavior.
Finished installing the OEM crankshaft sensor plate, angle offset changed from 10 to 6, so it was exactly 4 degrees ahead of the OEM plate. Put Loctite on the 4 bolts so they don't come out. No real play in the pulley boss, the harmonic balance doesn't look like it slipped at all.
I started the car and it ran for a few seconds before losing sync and stalling, it stalled with a crankshaft tab right next to the crankshaft position sensor. Checked the gap and it is exactly a credit card length away from the sensor, started the car again and it seemed to idle and rev up to 3k fine. Will check and see if it runs normally after dinner, hopefully the sync loss was a fluke of some kind.
Eating dinner and waiting for the rain to stop before testing it further.
Yeah, the issue is the same, actually a bit worse than before. I always got sync loss after merging onto the highway and cruising for ~15 seconds at 3000-3800 RPM, repeatable every time I get onto the highway. I am out of ideas to try, the crank log doesn't record any useful data, the crank sensor gap is perfect, the sensor is new. I had the car lose sync about 4-5 different times on a 30 minute highway drive, before it would really only lose sync once or twice.
I can't figure out how the crank log shows sync loss, there is a red tab for every sync loss that matches the datalog I take, does it only log the cam/crank pulse it has an issue with and associate a red line on the start/end of every sync loss? If so, 4 of my sync losses were caused by a missing crank signal and 1 of the later ones is caused by a camshaft signal miss. Screenshot of the crank log below. The extra long crank pulse at the very start matches the ~7 second loss of sync I had at the start, the rest of the sync losses were quick and only lasted a second or so each, which also matches the composite log. I am thinking of trying to drive back with no A/C on and see if that stops the issue, later in the day without A/C I usually don't lose sync, which leads me to blame the camshaft sensor. May order a ballenger motorsports cam sensor and re-do the wiring entirely because this is usually only occurring when it is hot outside w/ the A/C on while cruising. Also looking at the 36-2 trigger wheel due to this thread. I am going to try disabling the noise filter and see if that does anything to change the issue, I'm on the right track as the issue did change, even if it got worse.
Last edited by HowPrayGame; 09-11-2020 at 01:23 PM.
Lost sync multiple times around 3k RPM in stop and go traffic, so same issue essentially
Composite log looks similar to the issue with noise filters enabled. One crank pulse seems to be missing entirely, 4 misses on an existing crank pulse, 2 misses on the cam pulse.
I may try enabling the noise filter on the cam and see if it changes anything. Issue generally occurs when it is hot/I have A/C on, heavily suspecting cam sensor. Will need to figure out how to use the ballenger cam sensor with MS3 as it sends a different style signal. Also possibly going to disable adjusting the VVT cam based on injector timing if that doesn't do it. 36-2 is probably going to be my last resort as replacing the timing plate sorta sucks.
I wonder myself about the 36-2 trigger wheel! I haven't had time to troubleshoot but I hope to be able to soon and help you out if I find something on my end.
My thoughts are to try the cam sensor and also the trigger wheel.
This may apply to you guys or not but if you are having any kind of sync loss with a VVT engine, the first thing you need to do is get rid of the connector at the cam sensor. If ya'll done your research you would have found the numerous threads about this issue and the one that has the Spec Miata guys resolving the issue by getting rid of the connector. Again, I'm not saying this is going to solve your issue, but if you haven't done it yet, you need to. The best part is that if you have a soldering gun and tin, the potential fix is free.
The problem is heat at the connector terminals causes enough noise in the line to lose sync. It is the cam sensor specifically as it is getting doused by engine oil. But people with NB1's have reported the issue and their sensor is dry. Their issue was a little different as they would stumble and miss as opposed to losing sync and shutting off.
The factory connector needs to be taken off and the wires stripped back and pre-tinned. Then do the same to the cam sensor terminals. You will likely need to cut off the hood of the sensor. How much depends on how thin your solder iron is or how steady your hands are. Then tin your connections. You can leave it like that or fill it with epoxy. You can add a connector a foot or so away or wherever convenient but the sensor only has one bolt to unplug so it can stay with the harness.
Again, this is predominantly on the cam sensor of a NB2 engine but the connector for the crank sensor is basically the same and the noise can occur there too.
I did this to my VVT swapped NA8 and it was the magic bullet. Absolutely made the problem go away.
Agreed, all my signs point to cam sensor overheating/shitty connection to the sensor, going to order a ballenger motorsports cam sensor and see if I can get it working with MS as the signal it outputs is a bit different than the OEM one. Should accomplish the same thing as hardwiring it to the existing sensor, hope it works.
It comes with a connector kit that replaces the OEM one and is supposed to be less susceptible to overheating in general. I don't have a soldering iron and replacing the cam sensor with a nice one costs about the same as a nice soldering iron kit. I assume the signal differences aren't that big of a deal for MS as it also works for VVT with OEM computers from what I can tell.
I have only had a sync loss once directly after startup and it was almost certainly due to the timing plate change, never happened since that point. Always occurs on a hot day after the car sits in the sun for a few hours, and after driving for a good 10 minutes. Loses sync a few times then stops for the rest of the drive.
I think the soldering iron I bought costed me $90. I have used it frequently with the car mods I have made.
Also I think I figured out that with the turbo shield I made myself the heat channeled air from my turn signal intakes towards the cam sensor. That's when my issues started. So I am in favor of making the same changes to the wiring. I know my sensor works so I am going to fix my heat shield as well.
Hector, that's gotta be it. I zip tied the OEM connector to the sensor and on the same route that normally on a hot day would cause many sync losses, the car performed perfectly fine with no sync losses.
Hardwiring the sensor would solve this for good, or replacing it with the ballenger, assuming the connector they included holds up better than the oem one. I am going to run with a zip tied sensor for a while longer before calling it solved for good, but I am almost 100% certain that was the issue.
Damn, it could very well still be the sensor. My case of the connector being loose doesn't seem as common as the sensor heatsoaking, something internal to the connector heatsoaking/being loose, or the sensor just being bad. Even though the sensor came loose I couldn't really tell on the crank/cam logs for some reason
UPDATE - 5/12/2021
See https://www.miataturbo.net/megasquir...-issue-105025/
Issue was a failing replacement crank sensor/loose crank sensor bolt. Car now revs perfectly on very hot days and hasn't lost sync once with an OEM Cam and crank sensor.
Last edited by HowPrayGame; 05-12-2021 at 10:39 PM.
09-05-2020, 12:34 PM
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