Let's pick an RPM which is user-friendly.

If engine speed is 6000 rpm, the crank is making a complete
revolution every 10 milliseconds. Since the engine is a 4-cycle,
a complete Intake, Compression, Power, & Exhaust cycle
takes 2 crank revolutions - So the camshaft & distributor turn
at half the crank speed, or 3000 rpm.

Since its a 4-cylinder engine, an ignition event comes along every
90 degrees of distributor rotation, so...

3000 rpm is 1 rev every 20 milliseconds, so you'll have an ignition
event every 5 ms, a frequency of 200 Hz.

In practice, you'll see some phase jitter because of gear backlash,
contact bounce if you're using (gasp!) points, and the "advance" &
"retard" built into most mechanical distributors.

Still not clear? Tell me what you don't understand...

 Jack
--=20
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