RPM and pulses

Dear Fernando:

A four stroke engine will fire half the cylinders in each revolution.

David A. Smith

RPM is revolutions per minute. Divide by 60 to obtain revolutions per second. A four stroke engine has half as many firing strokes per revolution as the number of cylinders, while a two stroke engine has as many firing strokes per revolution as the number of cylinders. Only non -diesel engines normally have distributors. A relatively modern twist for four-strokes is to allow a wasted spark on the exhaust stroke - which can help complicate the issue in some few cases. This engine style sometimes goes with a coil per cylinder or a coil per cylinder pair.....

Clear as mud?

Sorry!

OK, try this (4-stroke) Sparks per sec = RPM X number of cylinders / 120

Brian Whatcott Altus OK

Dear Brian Whatcott:

Also Multiple Spark Discharge (MSD) ignition systems that fire the spark plug multiple times on the power stroke...

David A. Smith

FWIW,while this may be relatively recent in automotive applications, 4 cylinder, four stroke motorcycles have been doing this much longer. At least 30 years.

---------- Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com)