Fuel management system for variable ethanol octane enhancement of gasoline engines

Abstract

Fuel management system for efficient operation of a spark ignition gasoline engine. Injectors inject an anti-knock agent such as ethanol directly into a cylinder of the engine. A fuel management microprocessor system controls injection of the anti-knock agent so as to control knock and minimize that amount of the anti-knock agent that is used in a drive cycle. It is preferred that the anti-knock agent is ethanol. The use of ethanol can be further minimized by injection in a non-uniform manner within a cylinder. The ethanol injection suppresses knock so that higher compression ratio and/or engine downsizing from increased turbocharging or supercharging can be used to increase the efficiency of the engine.

1 - 37 . (canceled) 
     
     
         38 . A spark ignition engine which is fueled with gasoline and ethanol where fuel is introduced into the engine in such a way that liquid ethanol vaporizes in at least one engine cylinder and vaporization cooling from the ethanol enhances the octane number at a rate of at least 15 octane numbers for an increase from 0 to 100% in the ethanol fraction of fuel in the cylinder. 
     
     
         39 . The spark ignition engine of  claim 38  where ethanol is introduced into at least one engine cylinder by direct injection. 
     
     
         40 . A spark ignition engine which is fueled with gasoline and ethanol and where the fuel is introduced into at least one cylinder is such a way that the octane number is enhanced by use of ethanol at a rate of at least 30 octane numbers for a an increase from 0 to 100% in the ethanol fraction of fuel in the cylinder. 
     
     
         41 . The spark ignition engine of  claim 40  where ethanol vaporizes inside at least one engine cylinder and the octane enhancement from vaporization cooling increases with ethanol use at a rate of at a rate of least 15 octane numbers for an increase from 0 to 100% in the ethanol faction of fuel in the cylinder. 
     
     
         42 . The spark ignition engine of  claims 40  or  41  where ethanol is introduced into the cylinder by direct injection. 
     
     
         43 . A spark ignition engine where a first fuel is introduced into the engine by a first fuel injector which is a port feul injector and a second fuel is introduced into the engine by a second fuel injector
 where the second fuel has a higher octane number than the first fuel and where the second feul is introduced into at least one cylinder by a direct fuel injector.   
     
     
         44 . The spark ignition engine of  claim 43  where the ratio of the amount of fuel introduced into the engine by the second fuel injector to the amount of feul introduced into the engine by the first fuel injector increases with increasing torque. 
     
     
         45 . The spark ignition engine of  claim 43  where the fuel air ratio is substantially stoichiometric.