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

I am trying to figure out an appropriate crank trigger for my Vulcan 500. The engine is 180 deg. parallel twin. I plan to do squential COP. I'm using a cam sensor triggered off a cam lobe, so my cam sync signal cannot be changed. I believe this signal comes just before or just after cylinder 1 TDC. Being a 180 deg engine, cylinder 2 is approx at BDC before the power stroke when I would get cam snyc. I am looking heavily at what mxrob has done for a crank sensor (carving teeth in the flywheel) or I may try to press on a trigger ring.

Anyway to the question at hand: I was thinking of using a 36-1 crank trigger wheel. However since cam sync is coming from a sensor off a nice round cam lobe I don't know that cam sync will come during the missing tooth reliably. Forgive my ignorance if I've overlooked the obvious answer but, could I use more than 1 missing tooth to give a larger window for what may be a somewhat erratic cam sync signal, say a 36-3 crank trigger? From what I've read I think the answer is yes, but I'm not to sure of that.

I would go with a 36-2 wheel and try to put the cam sync in the middle, giving you +/-10 deg of slop. But if you feel there will be more slop than that, you can use a 36-3 wheel, though I haven't seen anyone ever do so.

triangles95 wrote:... I was thinking of using a 36-1 crank trigger wheel. However since cam sync is coming from a sensor off a nice round cam lobe I don't know that cam sync will come during the missing tooth reliably....

BTW, I have a 4 "tooth" crank wheel and 1 cam lobe sensor on the GTS, crank like this, shallow round drillings pass perpendicular to VR sensor, very short tooth time, bigger gaps between the teeth.
and it worked OK, eventually. I am not using B&G 2.890 at the moment on this bike, but will be trying it on the black bike later when other stuff arrives.

It might be possible to use this approach, as in have any no missing teeth.

I need missing teeth because I want to do sequential EFI with COP ignition. This requires a cam sync signal so µs can differentiate between the power and exhaust strokes. Reading The Friendly Manual, it says that the cam sync must come during the missing tooth(teeth). I want to use 36-N teeth so that µs has a more accurate picture of crank position since I plan to do ignition as well as fuel injection and more accurate ignition timing is obviously desirable. If for some reason I can't use a 36-2 or maybe 36-3 I would have to go down to maybe a 24-1 trigger wheel as it would have a larger gap for the cam sync, but at the expense of timing accuracy. Thanks for the pic of your 4 "tooth" trigger wheel that may give me an idea for an alternative. Are you running ignition with that 4 "tooth" wheel?

Somebody please correct me if I've got any of this wrong! I only think I know what I'm talking about.

triangles95 wrote: ... Are you running ignition with that 4 "tooth" wheel?

I was at the time when I was running B&G 2.890. BTW the original ECU ran wasted spark, and sequential injection.

I also ran wasted spark COP ignition, using a four channel ignition amp with the inputs paired.

Talking confused...I was looking at this,

Cam sync must arrive during missing tooth?

Peter Florance wrote:Cam sync must arrive during missing tooth?

[quote="From the "dual spark" section of the manual that also covers single spark. I'm assuming it's this way because the original controller did not do single spark."]c. M-N toothed wheel on input 1. The cam synch on input 2 must be placed so that it occurs during the missing teeth. Ignition starts on the tooth after the missing tooth. If a cam synch has occurred just before this tooth, it fires on Output 1, otherwise it starts with Output 2. Thereafter the outputs alternate. This setup provides the fastest startup because you don't have to wait for cam synch. Note that the cam detection polarity (aka. "input edge capture") is independent of the crank detection polarity, and you must specify both. [/quote]
This is in section 2c http://www.microsquirt.info/dualspark.htm about 1/3 of the way down the page. So unless I'm reading this wrong your cam sync must come during missing tooth(s).

here: http://www.megamanual.com/ms2/wheel.htm it looks like the number of missing teeth can be whatever you want it to be. I'll do some experimenting with a timing light to see if I need to have more than one missing tooth on a 36 tooth wheel. Right now unless someone corrects me, I see no reason why a 36-2 wheel wouldn't work. There really is no explanation of why you would need/want more than 1 missing tooth. The only reason I can come up with is for cam sync like in my situation I'm triggering off a round cam lobe instead of a sharp square tooth that may cause a bit of variation in when the cam sensor gets it's signal. This is amplified by the fact that the cam rotates 1/2 the speed of the crank so 10 deg of crank rotation is 5 deg of cam rotation.

Peter Florance wrote:Cam sync must arrive during missing tooth?

True on a microsquirt, not on sequencer.

Thanks for your input I'm going to try a 36-2 trigger wheel. Unfortunately due to my current financial situation it will likely be some time before I can move forward on this project. In the meantime if I can figure out how to trigger a timing light off the cam sensor I will get a better Idea of how much variation I have in the cam sync signal.

I'm finally getting around to continuing this project. Anyone know of a place besides bigbluesaw.com and emachineshop.com where I can send them my cad drawing and have them cut out a trigger wheel? Looks like both of the previous sites want $110-$120 for a trigger wheel. I was thinking it would cost about half that.