Single Cylinder Engine RPM Doubled

[Hardrocker2011]

Good Afternoon All,

As a school project, fellow students and I are outfitting a single cylinder Briggs and Stratton with Microsquirt EFI. The engine runs, as it was used last year for a competition. However, one problem is that the RPM appears to be doubled when viewed with Microsquirt's tachometer. We would like to fix this problem, so that we can get better resolution on the VE table and so that we know everything is accurate. For the crank position sensor, one hall effect sensor is being used. Additionally, it sounds like the engine is firing every other cycle as it sounds like it is running very rough. Any suggestions to fixing this problem would be much appreciated.

Also, I would like to add that I am unaware as to what input the hall effect is triggering (i.e. VR1 or VR2). I just saw the topic regarding that at the beginning of this forum section. I will check on that, if you believe that might be the problem.

Thanks Again!

Hardrocker2011

[grippo]

This sounds like a configuration problem. To solve it we need to know if the engine is 2 or 4 stroke, what tooth pattern the wheel has and a copy of your msq. Also you need to verify your Hall sensor is hooked up properly by looking at what pins on the Ampseal the sensor is tied to and comparing this to the Ampseal pinout and hookup diagram for Hall sensors.

[Hardrocker2011]

Thank you for the reply grippo.

The engine is a four stroke, and as far as the tooth pattern goes, there is one magnet installed in the flywheel. A copy of the MSQ is attached. I apologize as I don't have the engine in front of me right now. Therefore, I'm not able to see exactly what pin the hall sensor is hooked into. I will look into it tomorrow. Also, I'll look into where the magnet is installed in the flywheel.

Thank you for any additional information/suggestions you or any others provide.

Hardrocker2011

[Matt Cramer]

As this one gets one pulse per revolution, change the MSQ so it's set to a 2 cylinder (which would have one spark event per engine revolution). You'll have to rescale the fueling after this, of course.

[Hardrocker2011]

I checked the input from the hall sensor, and it was going into opto-in+.

Also, I tried changing the cylinder number to 2. The RPM still appears to be double. No timing light to verify this at this time, but the timing will be checked later. When cranking RPM reads at 600.

Also, we tried wiring into the VRIN2+ input. We did not get any response from the tach after an attempt to start it after making the change. Is there a way to change which input the tach reads? Also, we have been using the TunerStudioMS software package, if that makes a difference.

We appreciate your help, as we are all microsquirt rookies.

Thanks,

Hardrocker2011

[mxrob]

Looks as though your trigger wheel setting is zero?