It has the following engine enhancements&colon; matched pistons, a lightened flywheel and forged crankshaft. The pinion automatically disengages from the flywheel after operation. Evolutionary engineering changes included positive crankcase ventilation, a smaller flywheel, and an aluminum clutch housing. The drive shaft to the flywheel is in diameter. One of the primary limits to flywheel design is the tensile strength of the rotor. Several modern flywheel rotors are made from composite materials. Additionally a bigger clutch and a stepped flywheel were included. The , carbon fiber flywheel spins in a vacuum to eliminate friction. Regenerative braking has a similar energy equation to the equation for the mechanical flywheel. The early mills had a vertical shaft to take the power from the flywheel. This drove through a large flat flywheel and a friction drive. The flywheel stores the energy as rotational kinetic energy. Honda increased the diameter of the flywheel for more inertia. SVT specific cams, a lighter flywheel and low-restriction exhaust complete the picture. This is determined based upon the inertia of the flywheel and its angular velocity.