Fuel management system for variable ethanol octane enhancement of gasoline engines

A fuel management system for a turbocharged spark ignition engine where the fuel management system controls fueling from a first fueling system that directly injects fuel into at least one cylinder at a liquid and a second fueling system that injects fuel into a region outside of the cylinder, and

• where the fuel management system uses spark retard so as to introduce as a smaller amount of fuel from the first fueling system into the cylinder than would otherwise be necessary at a given value of torque.

A fuel management system for a turbocharged spark ignition engine where the fuel management system controls a first fueling system that injects fuel directly into at least one engine cylinder as a liquid and a second fueling system that introduces fuel into a region outside of the engine cylinder and:

• where there is a torque range where the fuel management system uses both fueling systems and;
• where in this torque range, as torque increases, the fuel management system increases the fraction of fuel that is introduced into the engine cylinders from the first fueling system so as to prevent knock that would otherwise occur and;
• where the fraction of fuel in the cylinders that is provided by the first fueling system as the torque is changed is substantially equal to that needed to prevent knock.