Megasquirt Support Forum (MSEXTRA)

Problem solved by swapping in my spare CAS.

Same plugs, same VR circuits. Can't see any physical difference between the two CASs.

Next step is to get back to sorting Traction Control

Update - Sync loss returned start of November 16 while at a track day. Conditions were high RPM, but not on the limiter, engine didn't misbehave at all but check engine light was flashing at me. Happened maybe a dozen times

I've installed new plugs, the BR10EG type 2 weeks ago. No issues so far

See how that goes

Now mid January, 2 months after new resistive plugs installed, no issue yet with Sync loss reoccurring.

Glad to hear something so simple fixed the issue. Keep an eye on the BR10EGs. Ive ran them on my 13BT for a couple years now and I somehow busted the porcelain tip at some point. The engine ran fine and wasn't damaged, but it might be worth inspecting them periodically. I was running 27+psi daily and and had over 50 dyno pulls and 3 months on the plugs. Car made 540whp and ran flawlessly. I would still recommend them.

Bumping this old thread to say that the sync loss is still happening.

Was back at the track again (I mentioned earlier in the thread I was at an event November 2016, this is the 2017 edition).

Sync loss happened most times I got the car up above 7500 rpm unfortunately.

Now running firmware 1.5.1.

I've had the ECU out of the car today to look at the sync loss issue. I attempted to install the JBPerf Dual VR 2.1 circuit but backed out. I had intended to use the unused MS3 DB37 pins 8 to 14 to run the 4 Crank/Cam signal wires into the case but unfortunately it appears that these pins have been grounded via the MS3 PCB. I'd need to install another plug into the case to install the Dual VR circuit. I don't understand the benefit of designing the PCB with these pins grounded. They could have been left unconnected beyond the PCB pad and the user could ground them if desired, or use for other purposes as appropriate. The dedicated power grounds are shown in the MS3X/MS3.0 hardware manual as being 15 to 19.

While I think about how I might neatly add another plug to my MS case I went ahead and looked at the pots on MS3 and MS3X for the 2 VR circuits. I followed advice on the DIYAutotune site here: https://www.diyautotune.com/support/tec ... -tests-vr/
The guide advises to adjust the zero crossing circuit to show between 1 and 2 volts on pin 3 of U7 (an op amp). I applied this to both Crank and Cam wheels and set pin 3 to 1.5 volts. I increased hysteresis a little from where it had been by tweaking R52 and MS3X so the pots were at about 90k rather than 95k. When I tried to start the car it would not start. I put an oscilloscope on the pin1 of both MS3 and MS3X U7 chips and was not seeing any output so I assumed the zero crossing was too high. I turned the pots again so the voltage on pin 3 was 0.6 on the MS3 and 0.8 on the MS3X. The minimum voltage I could get was 0.5, some distance from "true zero crossing". I wanted to give a little bit higher to the MS3X as it is the 2 tooth wheel connected to this board that is throwing the check engine light all the time. When I reinstalled the ECU back in the car this time it started straight up, so for me the DIYAutotune guide was not correct. I did notice though that a lot of the schematic info refers to U7 as MC34072, my board has an LM2904. I've bought a couple of the newer MC34072 op amps and will install when they arrive.

When describing this process I wanted to avoid talking in terms of turning pots clockwise or counter clockwise because of the issue I experienced early on with my Megasquirt life where the supplied components were not the same as those shown in the instructions, which became ambiguous, I lost the coin toss and installed the pots backwards. The direction the pots are turned isn't relevant as the actual voltage delivered to the comparator.

Just wanted to add that I have not had a sync loss check engine light after last post where I adjusted the pots