The original VW bug engines with breaker point/capacitor ignition has 4=20
cam lobes on the distributor shaft which turns at 1/2 crankshaft speed.=20
Therefore there would not be a wasted spark.

On 3/7/2011 4:59 PM, Michael Watterson wrote:
> On 07/03/2011 21:40, Andre Abelian wrote:
>   =20
>> Michael,
>>
>> I know one thing for sure that the rotor has 4 magnets and 1 turn of rot=
or will
>> fire 4 cylinder.
>> I just do not understand what does "Four stroke is 1 spark every two rev=
olution"
>> means?
>> can you give and example?
>>
>> thanks
>>
>> AA
>>     =20
> The four strokes
> Revolution 1
> INTAKE stroke  Piston descends and sucks in air and fuel (inlet valve ope=
n)
> Compression Stroke,Piston rises (all valves closed)  Piston rises and
> just before top dead centre, spark is applied
> Revolution 2
> Piston descends due to ignition of fuel/air mixture gas pressure
> Exhaust stroke (exit valve open), piston rises and pushes out waste
> exhaust gases.
>
> So each cylinder gets a spark once every two revolutions.
> With four cylinders, each compresses and gets a spark in turn, so 4
> sparks every 2 revolutions. Cam has 4 bumps for "points" or 4 magnets
> and distributor cap on same shaft, four contacts.
> *
>
> *
>   =20
--=20
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