> The biggest draw is probably compressing the air in the cylinders.
> Those pistons are still going up and down, even without the plugs
> firing.
I just thought about it for a minute, and I don't think this is the
case. Let's look at a four-cycle engine's cycles when no fuel is
ignited:
1. compression, valves closed: gas gets compressed by piston
2. combustion, valves closed: no ignition, therefore no combustion,
therefore the gas just compressed in 1. gets relaxed to its initial
volume, pressure, and temperature (both processes can be assumed to
be adiabatic, therefore no heat exchange with the engine block
takes place)
3. exhaustion, one valve open: gas gets pushed out, no significant
pressure required because the valve is open
4. suction, one valve open: gas gets pulled in, again no significant
pressure required
The entire cycle is symmetrical, so while the prop might have more
resistance from one cylinder (1.), another cylinder comes up with just
the required torque (2.). Even if the cylinders don't compensate for
each other, the torque averages out to zero over the rotation of the
engine.
I'm sure the biggest contribution to the torque with the engine off is
friction, primarily that of the cylinder sealing rings against the
cylinder walls, and maybe the resistance of the water cooling system,
which I guess is driven from the engine shaft.
Andras
===========================================================================
Major Andras
e-mail: [EMAIL PROTECTED]
www: http://andras.webhop.org/
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