RPM stands for rotation per minute, but rotations per minute of what?



I always thought itd be the wheels, but after actually thinking about it, after shifting gears the RPM goes down, when the wheel is spinning faster increasing acceleration. So what is the RPM referring to? Something in the transmission?

 

RPM is actually revolutions per minute and it measure the revolutions of the crankshaft in the engine. One RPM equals one crankshaft revolution so if you are at 3,000 RPM, the crankshaft is spinning 3,000 times a minute.

 

And the spark plugs are firing at half that rate. FWIW,