Larry Colen SEZ -
(With deletions)
>
> This made me hypothesize on why cars are more likely to predetonate
> going uphill rather than on the flat. In addition to the back force
> from inertia and drag, there is also the added force from lifting the
> car up the hill. With more force on the piston (and no predetonation)
> divided by the same area, there is more pressure in the
> cylinder. Likewise, a lighter flywheel could slightly reduce pinging,
> less rotating inertia, less force on the pistons, less cylinder
> pressure.
I think the higher pressure is caused not by force on the piston, but
by the fact that the extra load on the engine is causing it to turn
slower than it would without the load. At the same time, the throttle
is open farther, so more of the gasoline and air mixture has been
drawn into the cylinder. Therefore, the slowly-upward-travelling piston
compresses more of the mixture in the same space for a longer time, giving
the mixture more time to heat up and cause a diesel effect. I'd think
the effect from a lighter flywheel whould be the same as anything that
lightened the weight of the car as a whole, that is, quite marginal unless
you're talking hundreds of pounds. I offer this with the caveat that my
specialty is computer science, not fluid and thermal dynamics. :-)
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