In Reply to: Please explain the 5th gear issue (more) posted by //EricF on February 02, 2001 at 14:23:41:
the lightweight flywheel carries less momentum than a regular flywheel. therefore it carries less momentum when it spins, which means it will decelerate faster.
on the highway, when speed is constant, and you want to accelerate, the flywheel needs to spin faster. it is easier to spin it when there is already weight causing the flywheel to stay in motion.
in theory, the flywheel should be able to spool up faster at any speed due to less weight. but this is only true when accelerating from a stop. easier to push a lighter car from a stop than a heavier car. but easier to keep the heavy car in motion because the weight will carry it forward.
i hope this helps in the explanation. it's been too long since i was a physics major.