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

Where is a good spot for the cam trigger? I read on one of the pages that it said a little before TDC is best. But thats vague. Should I set the trigger at like 10 degrees TDC?

Anyone out there?? lol

If you are going to use a cam trigger, you don't need any missing teeth on the flywheel, and as long as you use a VR conditioner I cannot see you having any problems. There was an issue with the v2 MicroSquirt sensing ability and it's linked to the common ground that is shared with the VR sensors inputs (crank & cam), and if I understand correctly, if the VR pulses coincide, they interfere with each other.

I wouldn't go off that bolt hole/black dot you are proposing in your previous pic, as the other bolts would interfere with your positional detection.

24c wrote:If you are going to use a cam trigger, you don't need any missing teeth on the flywheel, and as long as you use a VR conditioner I cannot see you having any problems. There was an issue with the v2 MicroSquirt sensing ability and it's linked to the common ground that is shared with the VR sensors inputs (crank & cam), and if I understand correctly, if the VR pulses coincide, they interfere with each other.

I wouldn't go off that bolt hole/black dot you are proposing in your previous pic, as the other bolts would interfere with your positional detection.

Thats what I thought about the missing tooth deal. But I would still like to have a missing tooth just incase I cant get the cam sensor project going right.

I was planning on using a hall sensor for a cam sensor. The plan was to drill a hole into the cam gear and press a magnet into it. So even if I were to use a sensor that picks up the magnet those bolts would still interfere?

OK, I know a few guys out there swear by Hall sensors, but a VR cam sensor will work OK now, especially with the newer (not released v3 MicroSquirt) or by adding a MAX9926 VR conditioning board. I personally would avoid magnets, and use some lump of metal that is capable of being sensed. The cam lobe works fine now for me at very low cranking speeds (with VR conditioner or v3 MicroSquirt), so you could weld a blob, or use a taller headed fastener on one of the cam chain sprocket screws and achieve the same.

PS I have been asked to do a Husaberg engine for somebody, and after explaining the options, he's quite happy to have wasted spark with batch fuelling. At first I will be doing ignition only with a missing tooth wheel, unless I can easily fit a cam sensor, in which case I will have no missing teeth on the crank wheel/flywheel. To test this I will be getting a bare head (no valves) and turn the cam and see what type of signal/voltage I can achieve off the metal parts using a VR sensor connected to an oscilloscope.

24c wrote:OK, I know a few guys out there swear by Hall sensors, but a VR cam sensor will work OK now, especially with the newer (not released v3 MicroSquirt) or by adding a MAX9926 VR conditioning board. I personally would avoid magnets, and use some lump of metal that is capable of being sensed. The cam lobe works fine now for me at very low cranking speeds (with VR conditioner or v3 MicroSquirt), so you could weld a blob, or use a taller headed fastener on one of the cam chain sprocket screws and achieve the same.

PS I have been asked to do a Husaberg engine for somebody, and after explaining the options, he's quite happy to have wasted spark with batch fuelling. At first I will be doing ignition only with a missing tooth wheel, unless I can easily fit a cam sensor, in which case I will have no missing teeth on the crank wheel/flywheel. To test this I will be getting a bare head (no valves) and turn the cam and see what type of signal/voltage I can achieve off the metal parts using a VR sensor connected to an oscilloscope.

Well we ran wasted spark and batch fuel on our old custom ecu on the stock flywheel. But since this is for a formula SAE competition I would like to take it to the next level. Im still going to make thr crank trigger with a missing tooth just incase the cam sensor just doesnt work out. Right now its looking iffy because there is limited room in the head for anything. Where would you recommend placing the cam sensor?? At TDC? One page said it needs to be near TDC but thats kind of vague.

sn95.ohh wrote:... Where would you recommend placing the cam sensor?? At TDC? One page said it needs to be near TDC but thats kind of vague.

They are guidelines in the notes/info section, but ideally you want it, where it is easily detected under cranking, and the teeth aren't slowly down too quickly and confusing the MicroSquirt. If it was at TDC then this would be at the slowest point when the engine is under compression, so I reckon you'd want it quite a bit before TDC, so then x teeth later of the crank wheel you get tach/spark/etc, which would still be before TDC, and ideally x should be a low number or the missing tooth section, so giving a faster sync time.

Here is a link, to the newer 3.760 code documentation re triggering, and I think fig.4 is what you should be looking at, and an upgrade to the later code for your single would be beneficial. IIRC, one of the niceties of this with sequential, is cam sync is only used under cranking and for a few revs after this, thereafter it uses the crank trigger only, because the phasing is already known.

24c wrote:

sn95.ohh wrote:... Where would you recommend placing the cam sensor?? At TDC? One page said it needs to be near TDC but thats kind of vague.

They are guidelines in the notes/info section, but ideally you want it, where it is easily detected under cranking, and the teeth aren't slowly down too quickly and confusing the MicroSquirt. If it was at TDC then this would be at the slowest point when the engine is under compression, so I reckon you'd want it quite a bit before TDC, so then x teeth later of the crank wheel you get tach/spark/etc, which would still be before TDC, and ideally x should be a low number or the missing tooth section, so giving a faster sync time.

Here is a link, to the newer 3.760 code documentation re triggering, and I think fig.4 is what you should be looking at, and an upgrade to the later code for your single would be beneficial. IIRC, one of the niceties of this with sequential, is cam sync is only used under cranking and for a few revs after this, thereafter it uses the crank trigger only, because the phasing is already known.

Ok awesome. I remember seeing that page along time ago. Thanks for the info!