Depends on both which motor and which conditions.... Older vehicles are
generally one spark per cylinder per TWO revolutions... this would be in a
four stroke cycle engine. A two stroke cycle engine would have one spark per
cyclinder each revolution.

Here's where it gets cloudy..... Many modern auto engines use a wasted spark
ignition system.... One coil fires two cylinders. As one cylinder sparks at
the onset of the power stroke, its running mate sparks during the exhaust
stroke..... One spark per cylinder per revolution. Other modern engines
feature COP ignition systems (Coil On Plug). These systems feature a
multistrike condition at low rpm much like performance ignition systems. At
low rpms, the plug will fire more than once but only during the power
stroke.

Who knows what the future might bring? We see the hybrid Escape with what is
termed an "Ackerman" cycle engine... simply a variation on the "Otto" cycle
engine we have become familiar with but a significant advance in it's own
right. Bio-diesel, other alternate fuels, hydrogen fuel cells.... who knows
where this stuf will go next?

What engine?

Thanks for your help in this. I think you have been very helpful.