At a time when turbochargers are increasingly being touted along with engine downsizing for future road vehicle business, spare a thought for the old-fashioned supercharger. Driven directly or indirectly off the crankshaft, the air delivery characteristics of a positive-displacement, Roots-type supercharger are generally much more aligned with those of the reciprocating internal combustion engine. Consisting of two internal rotors in the shape of lobes rotating together, and phased using...