Tachometer calibration

[StanH]

Just a small query - I have set my engine information to Lycoming O-320 and the pulse/rev is set to 1.  My engine rpm is correct but aren't there 2 pulses/rev with a 4cyl four stroke engine? 

 

[dynonsupport]

The pulses per revolution are a function of your ignition system. We're not reading a sum of all the ignition events. Lots of ignition systems put out only one pulse per revolution on the tach wire even if they are 12 cylinder engines.

In the specific case of a magneto, it does fire twice per revolution, but the output is a positive voltage on one pulse and then negative on the other. SkyView only sees the positive pulse because of the way the detector circuit is designed.