Tach Time RPM value on Van's mechanical tach?

[David Carter]

Hi,

I have installed a JPI EDM-350 engine monitor with a magneto RPM pickup.

There is a calibration setting "average cruise RPM" with a description "Average cruise is based on a percentage of RPM redline. A one to one ratio for TACH TIME is achieved at this setting."

I have it set at the default value of 2400 RPM. I left the mechanical tach in for now to compare the readings. After about 2 hours tach time, the difference between the two is 0.1 hours.

Does anyone know at what RPM Van's mechanical tach reads one-to-one with wall clock time? Or is there another source for a "better" value for this on a Superior O-360?

Thanks,
David