Tach reading 2X the actual RPM

[spannbauer]

Hi guys,

This is my first post and I'm feeling really dumb for not being able to find this out myself. I've been searching the forums for a while with next to no help.

I've got my engine (95cc, two-stroke air-cooled single, RC airplane engine http://www.brisonrcengines.com/bri4u.htm) running, but at idle the RPM in TunerStudio is showing ~4000RPM. This seemed awefully high, so I threw a Tiny Tach around the spark plug wire and it read ~2000RPM which seemed much more believeable. I'm using a 36-1 wheel with a 12V hall sensor from DIYautotune to determine crank behavior.

Any ideas for what could be causing this? Please let me know what information I can provide that would help.

Also on a different topic, I would like to incorperate a CHT sensor to determine WUE because it's an aircooled engine. Has anyone done this or is there a better way? If so, do you have any tips on good, small sensors.

Thank you,

Shawn

PS: I've attached my .msq and .msl files of my most recent runs. I'm unsure as to whether I have the ignition settings correct. Is there another spot to specify "two-stroke" that I'm missing other than in "Fuel Set-Up --> Injection Control"? Another thing to not is the harsh misfires in the data-log where RPM drops to zero. This is actually visible in the toothed wheel and must be pretty aweful for the little engine

[grippo]

You have 2 problems- the rpm going to 0 is the more serious one and is most likely due to a vr sensor problem. Matt/ DIY can help with that.

The double rpm problem is due to a mis-configuration in the msq. The best option for your configuration is the Dual Spark option where you would set up as a single cam wheel. There is a lot of info in the manual on configuring 1 and 2 cylinder engines. I also included a writeup I did on this as an attachment that has the same info but is specifically for 1 and 2 cylinder engines.