M-0 Wheel

[Kyle R]

Hey Guys,

I posted here once before about trying to get a Yamaha Phazer engine setup. It's an odd fire 2 cylinder 4 stroke. It has a wheel on the crank with 12 teeth (no missing), with a VR sensor on it. The cam has a Hall sensor on it, and there is one recessed tooth in it (It goes down, not up).

We've been working on trying to get spark for the last 6 weeks. We've trouble shot everything we know to do. Our problem is that under M-0 wheel settings for dual spark we get nothing. No triggers and no tach signals. Last night we were able to get tach signals using "Single Crank Wheel" under dual spark options. The timing between the spark events is correct, and the RPM is accurate, so that felt pretty good. We were also able to set it up using "Single Cam Wheel" under dual spark options, so it appears that both sensors are providing usable signals. Under "dual inputs with cam sync" we had one coil being driven by the crank wheel and the other by the cam wheel, as expected. So we felt pretty good about that.

When we tried to set it up under M-0 with Rising Edge, we were unable to receive even one trigger or tach pulse. Everything went dead. We tried using falling edge, no luck, we tried playing with the tolerances, we tried manipulating the numbers in the "number of skip teeth" and number of teeth on the wheel, and it didn't change anything.

So I guess my questions are specifically about the M-0 wheel setup. Has anyone here successfully setup an engine using the M-0 wheel? If so, what did you do? There must be something we are missing. Last night we spent 18 hours trying to figure it out, had no luck. Any help is greatly appreciated.

Thanks,
Kyle

[Paul_H]

Kyle

Use 'falling or rising cam sync with tach or wheel' (depending on your cam input polarity) dual spark option and be sure to setup the crank sensor polarity correctly as well. Also make sure that the cam input occurs between the declared tach tooth and the previous tooth every time it changes state on the configured edge. Hope this is of some help to you.

[Kyle R]

Hey Paul, that helps, but I'm not sure exactly what you mean by making sure the cam input occurs between the declared tach tooth and the previous tooth everytime it changes state on the configured edge.

How do you define what is the declared tach tooth? Is that simply the tach tooth that occurs immediately after the "configured edge", which is just the rising/falling edge of the cam signal? How do you actually determine what

I've attached a picture of the signal we are seeing from our cam and crank sensor on the oscilloscope. How should we set it up with these signals?

Thanks for the help!

[Paul_H]

Hi Kyle
Sorry about that! I just re-read my post and it even confused me. The tach tooth is the first tooth after the cam sync input occurs,or it can be a tooth declared by using a number of delay teeth depending on your physical setup. Regardless of whether you are using delay teeth or not, the cam sync must occur between the same two teeth every time otherwise you will get a resync and this will make it impossible for the engine to rev past that point.
Your signals look good and with a 12 tooth wheel it is plain to see that you have plenty of time to fit the cam signal in between the required two teeth. If it is possible you might want to make some adjustment to centre the the cam signal between the two teeth just to allow for cam chain stretch or mal adjustment. Your scope picture tells me that your MT configuration would be rising edge for the VR input with a rising cam sync. Now get the spark output polarity right and you are laughing. Best of luck.

Paul

[Kyle R]

Hey Paul,

Thanks for clearing that up.We set it up as you recommended. It still doesn't give us any tach signals. We aren't able to adjust anything with the VR sensor to account for any chain stretch, but it looks like there is enough room that it *probably* won't be a problem...

We set up MT with a rising edge for the VR and a rising cam sync. We ran it like this- no luck. every 5 seconds of cranking we'd get a single tach trigger. I played with tolerances a little, and was able to get a tach pulse every 1 second of cranking or so, but I never got two consecutive pulses.

Does this mean that it sees an error every other full revolution, so it starts over? Or what does that mean? I can send you the MSQ file if you'd like to take a look at our setup.

Thanks for all the help paul, we're getting closer!!

Kyle

[Paul_H]

Hi Kyle
Yes, please post your current MSQ and also a datalog of your cranking attempts (if you can get one). Also post all other relevent info such as ECU type, software version and engine configuration including firing angles. This gives everyone reading this thread a chance to analyze your problem and hopefully contribute some helpful advice.

Paul

[Kyle R]

Hey Paul,

Here is what we've got from the Megatune. I'm going to try to do some data logging tomorrow, so I'll post that if I can figure it out.

The engine we are running is a twin cylinder 4-stroke, 180 degree odd-firing engine with a 12-tooth wheel with zero missing teeth. There is one tooth on the cam.

Take a look at our file if you can, and let me know what you think of it.

I've posted a picture in another post in this thread of the signal we are getting on the oscilloscope. Help is appreciated!!!

More to come,

Thanks,

Kyle

[Matt Cramer]

It looks like you've uploaded the wrong file there - while it has an MSQ extension, it definitely isn't an MSQ on the inside. I hope you haven't tried loading that one to the Microsquirt.

[Kyle R]

Hey Matt,

I'll check and see if I grabbed the wrong file. Thanks for the heads up.

[grippo]

Although the signal is clean, it has a long flat spot between peaks, typical of a wheel with a relatively small number of teeth. This flat spot is exactly near 0 volts, and the circuit puts out a pulse whenever a zero crossing occurs, so it could trigger too many pulses or pulses with wildly varying times. What the VR circuit does ideally is bias this signal up or down so the flat spot lies well above or below 0 volts, but not so much that the entire waveform is totally above or below 0, as could happen with a weak signal during cranking. I think it really illustrates the difficulty of the problems with general VR circuits. To design one that perfectly detects your signal is trivial - just bias it by .5 to 1.0 volts and it should work, assuming it doesn't shift around at high speed. But if it does it will probably move in one direction or another, so just bias it in the right direction for that. But this could totally screw up someone else's signal. So someone tries another processor and it works, so they think processor A sucks and processor B is the way to go; meanwhile someone else with processor B has a similar problem, processor A works for him, and he thinks processor B sucks. There is a need for a more intelligent VR processor and we are working on this. Meanwhile, after people confirm that your msq is ok, you can try tweaking component values. There are many posts on this.