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

Hi !

Project is Suzuki VS 1400 with microsquirt controlling fuel and spark. Problem is that I get inconsistent RPM reading while cranking. See pictures. Bike has pickup coil for each cylinder. Looked the signal with oscilloscope and it seems to be Ok ? I have tried resistors in series with coils.. No help at all

Might the problem be too long theet at the flywheel ? Any solution or do I have to modify the tooth ?

Yup - THAT's a long tooth! Unfortunately, while the bike OEMs love their long teeth with edge-detector circuits, the MS family is built around short teeth and zero-crossing detection. Zero-crossing is more accurate and repeatable at all RPMs, but is simply unable to deal properly with a long tooth.
You'll need to either switch to a Hall / 'geartooth' sensor, or add an edge-detection filter circuit.

Thank for your response.

So think I should cut the tooth ? is ~8mm long in right range `?

It´s odd firing T-twin with pickups for both cylinders. I´m using the dualspark mode.

Problem solved by adding 2x470k ohm resistors in series with the pickup coils. Cranking rpm stays at steady 230-233 rpm. Tomorrow have to try start-up.

Flywheel theet staid intact.

Congrats on solving your problem, but just a FYI for others, and that pesky long tooth problem.

I haven't got a long tooth flywheel to test, but I was experimenting with an Opel aka Vauxhall (GM) crank sensor a few weeks ago. It's Hall effect, 12V+, GND & 8V out BUT it's directional, which means if I rotate the sensor, I would see two trigger events for a "long tooth", but if I turn it through 180 degrees I only see one. Admittedly my "long tooth" is only 6 & 12mm long on my test rig at the moment, but it might be useful info for others in converting a long tooth flywheel. Opel part number is 9174621, and you can get them on fleaBay cheap enough. Their performance is excellent, I can trigger at 7 rpm on a 100mm diameter wheel with another make of programmable ignition. (Not using the MicroSquirt on this engine, as it only needs ignition...twin plugged flat twin)

Maick1 - is that 1x 470k resistor per coil, or 2 per coil? I'm absolutely fascinated by this; long teeth have been the bugbear of people trying to run uS and MS ignitions on stock bike trigger wheels for years, and I'm simply astonished that such a TRIVIAL modification is bringing what appears to be success. I await full-speed tests with slack-jawed hope!

24c - from what I gather, that's pretty much typical performance of any gear-tooth sensor, but still pretty good! Unfortunately that sensor is fairly large for a simple swap-in for OEM VR sensors - car VRs are big and clunky; bike VR sensors tend to be ... compact. Also, you listed your pinout as +12v, GND - and EIGHT volts output?

dontz125 wrote:Unfortunately that sensor is fairly large for a simple swap-in for OEM VR sensors - car VRs are big and clunky; bike VR sensors tend to be ... compact. Also, you listed your pinout as +12v, GND - and EIGHT volts output?

Hi buddy, just seen this, been dormant a while, but as I am playing with EFI again and using this sensor, thought I'd update the post!
Yep, I got the pinouts wrong, #1=8V (supposedly, but I've hooked it up to 12V too, no issues to date), #2 = output , and #3 = GND. Sensor is able to go in my bike heads with stepped adaptor bush, size wise its 25mm above the surface 24 below, and needs a Ø20mm bore to seal & comes with 500mm lead and 3 pin male JPT plug.

Interestingly, I struggled to get this Hall sensor to work this time, using the official useasydocs suggested layout, on a MicroSquirt v2 "Dual Tach Inputs". In the end, to get reliable start up performance, from 40 - 8000 rpm, I used the following connections.

Sensor 2 Output = VR2IN+
Sensor 1 Output = OPTOIN-
+5V (Vref) = OPTOIN+

Might help somebody else, but I'm wondering if this is a settings issue & some other combos might work too.

The v3 was a little harder, which again was surprising, as it worked great with the twin VR set up previously, so I thought it'd be a walk in the park with Hall sensors. Daft bit was I hadn't found the latest useasydocs document info, so I was forced to look at the MAX9926 data sheet and try and understand what was happening.
This latest update, link here was spot on, and BTW, I did use a pull up resistor referenced to Vref too

Happy holidays to you all, & glad the website is back.
Mike