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

R100RT wrote:Clearance to the stock cover is not much, probably in the range of 1/2" to 3/4", but if that simple set up with single tooth wheel works I'd be tempted to design your wheel along that basis.
Not sure if your proposed alternator upgrade had the permanent magnet style rotor, if so you might want to post that image for all to see, although I guess magnetic fields are magnetic fields regardless how their developed.

Regarding slippage, a wheel like that is so small that mass will be minimal and the puckering force developed by the retaining bolt (longer than stock for that) to the rotor center would probably keep it pretty well nailed in place.
Or, you could sandwich a waffle washer, or star washer between those surfaces to create some bite to ensure no movement develops.
You could be close to a solution there.

I'm using an alternator like the ones shown. I won't know the exact clearance till i get it, but it's basically an uprated Bosch.



The star washer or something similar may be an idea.

People install a (laser cut) spacer under the front cover to get more clearance for the trigger wheel.

les_garten wrote: The star washer or something similar may be an idea.

Don't bother, there is enough surface area to clamp the laser cut trigger wheel to the slip ring (the copper bit) of the alternator, and so it'll be just like a 4mm thick "penny" washer. I'd start looking for a slim VR sensor, as the wheel is virtually set.

PS I can help with a laser cut wheel if needed, still need to test the "pointed teeth version, but they made the hole to big, so I can't shrink fit it onto the pulley. Too much work, at the moment, and can't chat with them about it. Odd because all the other wheels have been a perfect fit using same CAD dim.

24c wrote:

les_garten wrote: The star washer or something similar may be an idea.

Don't bother, there is enough surface area to clamp the laser cut trigger wheel to the slip ring (the copper bit) of the alternator, and so it'll be just like a 4mm thick "penny" washer. I'd start looking for a slim VR sensor, as the wheel is virtually set.

PS I can help with a laser cut wheel if needed, still need to test the "pointed teeth version, but they made the hole to big, so I can't shrink fit it onto the pulley. Too much work, at the moment, and can't chat with them about it. Odd because all the other wheels have been a perfect fit using same CAD dim.

Are you getting them made here?

http://www.trigger-wheels.com/store/

Have you done a BMW with Microsquirt?

les_garten wrote: Are you getting them made here?
Have you done a BMW with Microsquirt?

No, local to me. DIY on CAD, dxf file to laser cutter.
Working on a Panhard though, sort of similar.

If you have a 1 position "Flying Magnet" wheel, is it less accurate than a 36-1 wheel?

Do more teeth help?

les_garten wrote: Do more teeth help?

They can do, and obviously if you have lots of cylinders then you really do need more. The engine isn't rotating at a fixed speed, it cycles at different speeds essentially accelerating and decelerating within its cycle. If you have more teeth, the ECU software can see these changes and offer more accurate timing of events, be it fuelling or ignition.

As you have a flat twin, IMO it won't be as critical. Motorcycles from OEM manufacturers have spatial problems too, and they work off less teeth than car manufacturers to solve this. It's not unusual to have 8 to 12 teeth on a four cylinder motorcycle, and one of mine had just 4 with a cam sensor.

It is generally regarded as good practice to have a tooth width about the same diameter as the sensor tip, so as you have a restricted diameter available, you can quickly work out the circumference, and do the maths to see how many teeth you can create.

I personally, would find a suitable sensor that you could mount in that space and then work backwards re the diameter you need, and then the teeth number could be calculated.

Because it's within close proximity to the Alternator, would it be better to do a Hall system over a VR?

les_garten wrote:...would it be better to do a Hall system over a VR?

Again, a personal choice, I had problems with a VR sensor on my cam lobe using the v2 MicroSquirt, but the factory OEM doesn't. The v3 MicroSquirt is well suited to VR sensors now, as the hardware is very improved now. Hall sensors are not quite as rugged, re temperature, but they have worked well for others. I use VR sensors on my projects because they are cheap, and easily fit my applications.

The noise issue will be determined by other factors, how you route your wiring, how noisy is the alternator in reality. I cannot say which is better, but if you started with a cheap VR, and it works great you are onto a winner. If it doesn't, you'll have to spend a little more money. MicroSquirting is essentially a DIY project, although there are more people doing it now, so the knowledge base is improving, but some experimentation will always be necessary, especially when converting older carbed engines to EFI.

I was mainly wondering if one was more immune to noise than the other.