MicroSquirt.com read only forum (Jan.15,2018)

Thanks Grippo, I was going to try the cam tooth =84, or 83 even, to give a little more lee-way, but kinda forgot, and didn't fully understand the possible outcome. I will try 84, but if you are sure the signal is causing a double trigger, I can make a bracket and just dump that CDI VR sensor, (if it is a sensor desighn problem, that is). And mount in a different sensor, like my trigger wheel uses. Also would "tach signal mask" adjustment help?
You make sense about the sync loss, never saw a trigger fix count, maybe a rare sync count down, but the tach count always reset to 0, as did the tach gauge. This all happens over like 500 milliseconds, as the backfires are so fantastic, one would have to be senseless to hang on the throttle, and hard to see what is going on.

"tach signal mask" won't make any difference in dual spark mode and anyway only applies to the first VR channel, which doesn't appear to be the problem.

If changing the Cam_Tooth doesn't work, a different sensor is worth a try. As is putting a resistor across the two VR2 wires, try 1K, 5K and 10K ohm in that order. I would look at the scope as I was doing it and see if/how it changes the signal.

Great minds think alike! ha ha! I am happy to say (knock on wood) that switching to 84 on "cam tooth" eliminated the resets at 4600rpm, and runs clean up to rev limit, tried it many times, never faulters, although I have not yet had it under a load, but have finally been able to tune the fuel table and other tuning parameters. Only issue I have now is that it does faulter when starting a lot, usually seems timing gets way too advanced, and starter bucks, but always seems to be synced right when it runs,which is good, as this is a high compression turbo engine, and even a few dergrees off some times could mean disaster in a hurry. Ohter issue is timing seems to be limited to 30 btdc, which is about the limit I would program anywhere on the table, but with the defaults running, even at 35 degree btdc commanded, I only read 30 with a timing light. Not a big issue, as 30-32 would be my max anyway, but just curious.
Anyway, would rather fix the problem with the sync vr, rather than compensate with settings, and was contemplating the resistor thing, but was under the impression that the resistor went in series on one line of the vr signal, but it looks like you say it goes across the two vr leads. I will probabally try some time with the scope on it, I have one of those rotary variable resistors somewhere.
I think this is mostly rectified, but have yet to load the engine, and drive it once, but atleast it starts (at least somewhat OK) with consistant timing, and revs to redline. I am waiting for my new flywheel to arrive, and will have to machine down the sync hump again, so I'm not able to button this up yet, but should have a grasp of what to look for, barring anything new and wierd shows up! I will let you know in a while how it all ends up.

I was afraid the change to T84 would hurt starting a bit, so scoping it is a good idea.

Timing shouldn't be limited to 30 deg unless the trigger offset isn't right, in which case your timing wouldn't be right. I believe you used the Auto Trigger feature, but if you didn't then you can get into this sort of situation by an improper configuration even though it gives correct timing.

With the old microsquirt there were al sorts of ways to try to get the VR to work with resistors, diodes, etc. With the V3 microsquirt a resistor across the VR inputs is the way to fix the high rpm problem.

Just a quick update....Had it on the chassis dyno this weekend to tune in the VE table, and everything pretty much worked flawlessly, Started great almost everytime, and reved to redline very smoohly, and it has never run so smoothly, quiet, and exhaust temps much, much cooler. I still have cam tooth set at 84, and haven't installed a resistor on the sync yet either. (just worked so good lately, I didn't persue that yet). My new flywheel hasn't shown up yet, (on backorder now), so have to deal with that yet, I think I'll narrow up the sync tooth up a little more when I cut it down.
I am using autotrigger, and trigger offset is adjusted correctly, so I'm not sure why the timing didn't go higher than 30, but my map is all under that now anyway, so haven't really had a reason to persue that either.

So I have been tuning this project, and messing with different turbos and such, and recieved my new flywheel, so have installed it. It runs good, but it still has a bad habit of throwing some very advanced sparks while cranking, like about 90 degrees before TDC. This causes a violent crank "decel" on that event, and with a normal crank speed of 4 to 5 hundred rpm, is creating some major damage to my starter, block and flywheel. I cringe now every time I crank the starter, fearing the sound of a kickback.
I tried either 85, or 84 cam tooth, but what I don't understand is where is it coming up with such a far off calculation? It throws out anything other than whats between cam tooth and tooth 0 right? If it should ever be off, I understand it could only be off by one or two teeth (3-7deg), not the 90 some it seems to pick at times. It seems to be off maybe every 4 or 5 times on average. It is always right otherwise, and starts almost instantly, This problem has really always been there, just rears its head randomly, and tried both "calculated" and "trigger rise", the latter of which was didn't really work well at all.
You can sometimes get it started when it "bucks" if you keep grinding on the starter, (but I have a broken parts sympathy reflex now, so I instantly quit cranking) and will eventually get it right, and start and run good.
I noticed that sync status does change right before a miss-timed spark start attempt, and get a few -trigger fix counts, but those always show up after the crank stalls from the over-advanced sparks. I noticed it will even re-sync with the coil dissconnected while cranking, usually after the first second or so, 1-2-3-3-3-3-3-3-2-3-3-3-3-3-3-3-3-3......but seems to be les frequently then....probabally coincidence.
I would be very happy with this setup, if not for these starting woes.. if not for the parts-busting damage it is causing, I could care less about a few hicups while cranking. Any thoughts are appreciated!

If you are sure the trigger+/- counts only after rpm goes to 0, then it has to be that it is losing the 1 tooth crank sync. Causes for this could be: too weak a signal at low rpm, noise coming from the starter or ignition. Backfires are probably caused because if there is noise on the cam signal then that will tell the ecu that tooth is tooth 1, and it could be off anywhere from 0 to 360 deg. The tooth 84 only protects after sync, before sync the ecu hasn't a clue where the engine is. So it will only find out after it has gone round 360 deg and no crank sync shows up - and the real crank sync won't be likely to show up because the ecu could have gotten the first(noise) crank sync on any tooth and after 1 rev it likely won't be anywhere near the real tooth 84. So it loses sync and repeats.

All I can think of right now is to make sure the VR wires are routed away from ignition wires and starter wires. Also, if you can scope the crank sync going into the ecu and on a second channel scope the VR2 output from the VR chip (this is what the processor sees). I realize this is very difficult to do and you need a decent quality two channel scope. I will ask Bruce if he has any other suggestions.

I didn't get back here quick enough, as I now have my tail between my legs. I failed to analyze the most basic settings of timing advance, I had the lowest rpm bins set at 8 deg btdc, (thought it was 5) but realized that this is a very large one cylinder engine, and apparently any amount of advanced timing is going to cause a major kick-back. I set all the lowest bins to 0, and havent had but maybe one or two slight kickbacks during crank. I can live with that. I also have been looking at the compression release mechanism, and it seems to not be working al the time, near as I can tell, which might not be helping either.
Either way, it now seems to work good, still have cam set to 84, as resistors didn't change the waveform much, but as a side note, I already had a different sync sensor all rigged up, and produced the same odd waveform as shown in the jpeg earlier...food for thought for someone else....
I think I can now say I am happy with this setup, and would think that an M-o setup would be very popular and easy to set up on many one and 2 cylinder engines, that had a CDI ignition, as there already is a sync generator there (CDI trigger) and a high res trigger (ringear) But apparently I am the only one trying it, now it has been proven to work!
One other non-related thought, with an M-O waste spark setup such as this, what should you be setting injector delay, and MAP or MAF sampling delay too, as MS doesn't know anything more than 360 degrees? I set both to 180, thinking its a happy medium....

Over the years there have been many people successfully running your M-0 + crank sync setup. But when you have 2 sensors you double the chance that one will give a problem.

As far as the map sample and injection timing, the most important thing about map sampling is to sample it at the same point on the 720 deg cycle. That's impossible with wasted, so the best you can do is sample at a point such that you get the least variation and the lowest value. On sequential this would be 540 deg after TDCC, which is BDC on the intake stroke. But not getting the lowest value can be tuned out in the ve table, getting a lot of variation can't be tuned out. I don't know where the optimum point would be on your engine. As far as the injection, from what we have read and experienced the timing of this is not critical over most of the 0-720 deg range. Where it becomes critical is when you inject during the valve overlap period, allowing raw fuel to get into the exhaust. So pick a point such that on either the first or second rev you will avoid the overlap region as much as possible. For sequential, auto engines oems generally inject on the closed intake valve for 3 reasons: avoid directly injecting on cylinder walls causing ring and wall wear; atomization of fuel when it hits the hot intake valve; it guarantees minimum fuel will get in the exhaust. I don't know if there would be other considerations for a 1-cylinder engine.

Just a quick note to update the status of this project. I pretty much have everything now buttoned up, and have it running really good, (although I haven't even touched the default crank PW and ASE, which seem really good anyway) It now starts well, and revs flawlessly to redline, and beyond. I have driven it around some, and works great.
I guess the take home message here is, with M-O crank sync setup, use "cam teeth" = M, or maybe (M)-1. Remember this is the V 3.770
If you get un-intended rpm re-sets, check your trigger signals for "noise" , and when dealing with large bore single cylinder engines, ( I'm thinking Harley like bikes too) try 0 degree timing during cranking for more smooth cranking.
These are a few things I learned during this project, hopefully helping out somebody else down the road.