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 - 98 . (canceled) 
   
   
       99 . A turbocharged or supercharged spark ignition engine system which uses both port fuel injection of gasoline from a first source and direct fuel injection of an anti-knock agent that is a fuel from a second source comprising:
 a spark ignition engine;   a turbocharger or supercharger;   means for port fuel injection of gasoline into the engine from the first source;   means for direct fuel injection of a liquid anti-knock agent which is a fuel from the second source;
 wherein during part of the engine operating time, the engine is fueled both by gasoline and the anti-knock agent that is directly injected; and 
   a fuel management system which increases the relative amount of anti-knock agent in the engine with increasing torque so as to prevent knock; and   where the engine is operated with a substantially stoichiometric fuel/air ratio.   
   
   
       100 . The engine system of  claim 99  where the anti-knock agent is the sole or partial constituent of a liquid which is contained in the second source and where the liquid is a fuel which is suitable for operation of a spark ignition engine without simultaneous use of the gasoline. 
   
   
       101 . The engine of  claim 99  where the second source contains methanol. 
   
   
       102 . The engine system of  claim 99  where the second source contains ethanol. 
   
   
       103 . The engine system of  claim 99  where the fuel management system employs a microprocessor for control of the relative amount of anti-knock agent in the engine and uses closed loop control with a knock detector and; where the fuel management system minimizes the amount of anti-knock agent that is used over a drive cycle. 
   
   
       104 . The engine system of  claim 99  where the anti-knock agent is an alcohol and is the sole or partial constituent of a liquid which is contained in the second source and where the liquid is a fuel which is suitable for operation of a spark ignition engine without simultaneous use of the gasoline. 
   
   
       105 . A turbocharged or supercharged spark ignition engine system which uses both direct fuel injection of gasoline from a first source and direct fuel injection of an anti-knock agent from a second source comprising:
 a spark ignition engine;   a turbocharger or supercharger;   means for direct injection of gasoline into the engine from the first source;   means for direct fuel injection of a liquid anti-knock agent from the second source;   wherein during part of the engine operating time, the engine is fueled both by gasoline and the anti-knock agent that is directly injected; and   a fuel management system which increases the relative amount of anti-knock agent in the engine with increasing torque so as to prevent knock;   where the engine is operated with a substantially stoichiometric fuel/air ratio.   
   
   
       106 . The engine system of  claim 105  where the anti-knock agent is the sole or partial constituent of a liquid which is contained in the second source and where the liquid is a fuel which is suitable for operation of a spark ignition engine without simultaneous use of the gasoline. 
   
   
       107 . The engine system of  claim 105  where the second source contains methanol. 
   
   
       108 . The engine system of  claim 105  where the second source contains ethanol. 
   
   
       109 . The engine system of  claim 105  where the fuel management system employs a microprocessor for control of the relative amount of anti-knock agent in the engine and closed loop control with a knock detector and;
 where the fuel management system minimizes the amount of anti-knock agent that is used over a drive cycle.   
   
   
       110 . The engine system of  claim 105  where the anti-knock agent is an alcohol and is the sole or partial constituent of a liquid which is contained in the second source and where the liquid is a fuel which is suitable for operation of a spark ignition engine without simultaneous use of the gasoline. 
   
   
       111 . A spark ignition engine which is fueled with varying ratios of gasoline and ethanol and where the ethanol is directly injected in such a way as to provide an octane enhancement at a proportional rate of at least 4 octane numbers for every 20% of the energy of the fuel in the cylinder that is provided by ethanol 
   
   
       112 . The engine system of  claim 111  further including a turbocharger. 
   
   
       113 . The engine system of  claim 111  where spark retard is varied as the ratio of ethanol to gasoline is changed. 
   
   
       114 . The engine system of  claim 111  where the engine is operated with gasoline alone. 
   
   
       115 . The engine system of  claim 111  where the ethanol is injected in such a way that the octane enhancement from evaporative cooling is greater than octane enhancement from the intrinsic octane of the ethanol. 
   
   
       116 . The engine system of  claim 111  where the ethanol is in the form of an ethanol-water mixture. 
   
   
       117 . The engine system of  claim 111  where gasoline is directly injected