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

Hi all,

I am working on converting a small one cylinder engine (Honda GX-35) to be electronically fuel injected. My setup is MS-II 2.888. I have the 3.57 main board. I am using a hall sensor to get rpms. There are preexisting magnets on the flywheel that are used for the magneto.

My biggest problem right now is that my RPM reading on the computer seems to be double the actual RPMs (I measured the RPMs with another handheld sensor). I have tried to change the number of cylinders as was suggested in another post, but this did not fix the problem.

I would appreciate any ideas on how to proceed. This is my first post so let me know if I need to provide more information.

Thanks.

Try changing the number of cylinders to 2, since you are getting two pulses for each engine cycle. Yes, it will run just fine that way.

Thanks for the advice. That seems to have worked, but I had to double the required fuel. Is this typical? I think this makes sense because Megasquirt now thinks that I have two cylinders with half of the displacement instead of one cylinder with all of the displacement.

Unfortunately, now I think my MAP sensor isn't working correctly. While idling, the MAP is reading >90kpa. I was under the impression that MAP should be low during idle. I was hoping someone could advise me on this situation. My only thought is that due to the small displacement (35.8cc), the engine does not create much vacuum.

Single cylinder engines often don't have a clear MAP reading at idle, and the having to adjust the fueling after correcting the RPM is perfectly normal.