 In the case of the Mustang the air being forced through the supercharger air intake was first compressed by the supercharger's first stage, or "low blower".The intercooler stopped the compressed mixture from becoming too hot and either igniting before reaching the cylinders or creating a condition known as knocking.Two-stage refers to the use of two impellorson a common driveshaft in effect constituting two superchargers in series; a Bendix-Stromberg pressure carburetor injected fuel at through a nozzle direct into the supercharger where the first-stage impellor compressed the air/fuel mixture.