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

can i use a 18-1 trigger wheel on a 4cyl motorcycle? my other option it now to make a 24-1 wheel if the other cant work. just not sure what i am doing wrong, or not right?..help please!!! thanks.

Hi turbo-max
I can't see why not, it's divisible by two, so if mounted on a crankshaft on a 4 cylinder, you'd be looking at a wasted spark every 180º.
I use an 18-1 on my Panhard engines now.
Mike

Is this a crank or cam mounted trigger wheel? Most code versions allow an 18-1 crank wheel, but for four cylinders, an 18-1 cam wheel usually is not supported.

Matt Cramer wrote:Is this a crank or cam mounted trigger wheel? Most code versions allow an 18-1 crank wheel, but for four cylinders, an 18-1 cam wheel usually is not supported.

this is crank mounted, i HAD started out with trying with a 36-2, but there just is not enough room to get the split between teeth, so i cut it down to 18-1, but still have about the same failed results would a 24-1 or 24-2 be an option? (the wheel is only 3" diameter) thanks for your help in advance....so confused

Hi turbo-max
It seems that the fault is elsewhere if other wheels don't work. I like to aim for a 50% on-off tooth pattern, that way it provides a consistent signal no matter what RPMs.
Do you have the use of an oscilloscope?
Any pictures of your install?
You could always mount the wheel in a cordless drill and hold the sensor near it, and then hook this up for testing (if you haven't got a test rig).
Mike

24c wrote:Hi turbo-max
I like to aim for a 50% on-off tooth pattern, that way it provides a consistent signal no matter what RPMs.
Mike

care to elaborate a bit more?

I use an Opel/Vauxhall or GM Hall sensor, that has more than one sensor in a discrete package. To reduce errors it uses two sensors and the leading and trailing edges of the wheel, so the tooth gap to toothed area isn't a 50% metal 50% air relationship.

It's not applicable to VR sensors, as you ideally just match the tooth width to the metal sensor tip, but you can see this using an oscilloscope no matter what you have. So in my case the Hall sensor produces a square wave, and I like to keep the time on vs time off the same. That's all, but it works for me, as I get no jitter, and can now detect RPMs from 7-23000 using my test rig with one quirky ECU, and with slightly higher start speeds with Microsquirts usually 49 RPM in Tunerstudio, but this is a software function, because I'm sure it's configured to start around 50 RPM.

Over the years, I realised having a stable trigger wheel design is the most important aspect when starting off, and so I build mine to give good performance at any speed or air gap, which is why you'll see me posting about building a mechanical test rig and using an oscilloscope ideally to tweak this area.

Mike