The Science Of Boost

By design, reciprocating engines are air pumps. They compress the aspirated air-fuel charge, ignite it, convert this expansion of hot gases into mechanical energy, and then expel the cooler, lower pressure gases. The amount of energy converted is determined by the pressure exerted on its pistons by combustion and the length of its expansion cycle. By increasing how aggressively a given mass of air-fuel charge is compressed, higher combustion pressures are achieved, allowing more energy to be extracted and thus creating more mechanical power output. ROOTS SUPERCHARGER In 1859 two brothers Philander Higley Roots and Francis Marion Roots founded The Roots Blower Company in Connersville, Indiana. Roots superchargers operate by pumping air with a pair of meshing lobes resembling a set of stretched gears. The incoming air is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust of the blower. TWIN-SCREW SUPERCHARGERS In 1935, Swedish engineer Alf Lysholm patented a new air pum