In the quest for faster cars, many enthusiasts will have their flywheels lightened. Why? Because a lighter flywheel increases the rate of torque applied to the drive wheels. How? It increases the efficiency of the drivetrain by reducing inertia. This is important as it will accelerate you car faster than the identical engine with a heavier flywheel. Also, if you are going to lighten a flywheel, it's much more effective to remove weight from the outer edges than the interior. This is due to the "leveraging" effect that mass has from the center of rotation. Like an ice skater spinning with their arms out, and as they bring them in they spin faster - same energy, faster rotational speed.

The downside of this is that taking off from a dead start is more difficult, because there's less energy at the clutch (energy=(1/2) mass x velocity-squared (.5 x m x v^2)). Decrease the mass, increase the speed (revs). Underdrive pulleys and lighter wheels help acceleration using this same principle - no more torque at the crank, but delivered to the wheels faster. Lighter wheels have the same effect, but to a smaller degree.

Technical Dept Home