On the contrary, a lightened flywheel is one of the cheapest performance
improving mods you can make, since the rotational inertia goes up with the
square of speed, there is a whole lot of energy stored in the rotating mass
of a drivetrain. A change of 5 or 10 pounds of flywheel weight has the
effect of hundreds of pounds at engine speeds. Just like lighter wheels/
tires shortens braking distance, a lighter rotating mass in the drivetrain
quickens acceleration. The less weight that is spinning the less energy to
dissipate when braking. There is a tradeoff though, acceleration is both
positive and negative, so the lighter the rotating mass of the drivetrain
the quicker it accelerates and the quicker it decelerates (negative
acceleration) this means that you will lose more road speed up a hill in the
same gear.
So in short, a lighter flywheel makes your performance more dependant on
what gear you are in. It is kind of like the difference between a low
revving v8 and a high revving I-4. The V8 has the torque to accelerate all
the time, while the I-4 is dependant on keeping the revs up to make power.
Because of this, the lighter the rotating mass of the drivetrain the more
you will have to shift to maintain speed up a hill , or to accelerate out of
a corner; you just don't have the same amount of energy stored up in the
flywheel to allow you to 'cheat' instead of downshift.
This isn't generally a problem, as people wanting more power are usually
willing to shift a bit more, but it can be a problem with a wide ratio gear
box because you may find that there are certain times where the car wants to
be in between gears and so you are forced to work above your peak power band
to keep the revs up. All of this is, of course an extreme example, most of
the time all you see are faster speed changes.
James Nazarian
71 B tourer
71 BGT V8
85 Dodge Ram
----- Original Message -----
From: David Breneman <idcb@airborne.com>
<snip>
>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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