Fuel management system for operation of a spark ignition engine. The system includes a source of gasoline and a source of anti-knock fuel. A proportioning valve receives the gasoline and the anti-knock fuel to discharge a mixture having a controlled gasoline/anti-knock fuel ratio. A single high pressure pump receives the mixture and delivers the mixture to an injector. A fuel management control system controls the proportioning valve and the injector for injection of the mixture into a cylinder of the engine to control knock. A preferred anti-knock fuel is ethanol.