Andre Abelian wrote:
> I just do not understand what does "Four stroke is 1 spark every two
> revolution" means?

This is from the basics of how four stroke engines work.  The piston goes u=
p
and down twice (and the crankshaft therefore around twice) for each complet=
e
cycle of what happens in the cylinder.  The cycles are intake, compression,
power, and exhaust.  Whatever performs the timing related to this full cycl=
e
has to do it at half the engine speed.  This includes the cam shaft and the
distributor rotor.  The cam shaft manipulates the valves to let gasses into
and out of the cylinders at appropriate times, and the distributor rotor
switches one of the sparkplugs into the spark circuit each spark.  It
usually also controls the spark timing.

So if a 4-cylinder 4-stroke engine is spinning at 10Hz (600 RPM), then the
cam shaft and the distributor rotor are spinning at 5Hz, sparks happen at a
20Hz rate, but each cylinder is sparked at 5Hz.

--=20
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