Optimized fuel management system for direct injection ethanol enhancement of gasoline engines

Abstract

Fuel management system for enhanced operation of a spark ignition gasoline engine. Injectors inject an anti-knock agent such as ethanol directly into a cylinder. It is preferred that the direct injection occur after the inlet valve is closed. It is also preferred that stoichiometric operation with a three way catalyst be used to minimize emissions. In addition, it is also preferred that the anti-knock agents have a heat of vaporization per unit of combustion energy that is at least three times that of gasoline.

What is claimed is: 
     
         1 . A fuel management system for a turbocharged spark ignition engine that employs a first fueling system that directly injects fuel as a liquid into at least one engine cylinder and a second fueling system that introduces fuel into a region outside of the cylinder where:
 during part of the drive cycle there is a range of torque where both fueling systems are used at the same torque and the fraction of fuel in the engine cylinder that is provided by the first fueling system is increased so as to meet the requirement for increased knock resistance as the torque and speed of the engine are changed and;   where a control system using information from a knock detector is used to increase the fraction of fuel in the engine cylinder that is provided by the first fueling system.   
     
     
         2 . The fuel management system of  claim 1  where the increase in the fraction of fuel in the engine cylinder that is provided by the first fueling system so as to prevent knock as increased knock resistance is required is minimized by dosed loop control. 
     
     
         3 . The fuel management system of  claim 2  where a microprocessor and open loop control used in the control system. 
     
     
         4 . The fuel management system of  claims 1  and  2  where the highest fraction of fuel from the first fueling system is provided when the highest knock resistance is needed. 
     
     
         5 . The fuel management system of  claim 4  where the first fueling system alone is used when the highest knock resistance is needed. 
     
     
         6 . The fuel management system of  claims 4  where the highest fraction of fuel from the first fueling system is utilized when the engine is operated at low rpm. 
     
     
         7 . The fuel management system of  claims 1  and  2  where when spark retard is decreased the fraction of fuel provided by the first fueling system is increased. 
     
     
         8 . The fuel management system of  claims 1  and  2  where the second fueling system uses port fuel injection. 
     
     
         9 . The fuel management system of  claims 1  and  2  where gasoline is introduced into the engine. 
     
     
         10 . The fuel management system of  claims 1  and  2  where ethanol is introduced into the engine. 
     
     
         11 . A fuel management system for a turbocharged spark ignition engine that employs a first fueling system that directly injects fuel as a liquid into at least one engine cylinder where the injection occurs after at least one inlet valve for admitting air to the cylinder has closed and a second fueling system that introduces fuel into a region outside of the cylinder and;
 where during at least part of the drive cycle there is a range of torque where both fueling systems are used at the same torque and the fraction of fuel in the engine cylinders that is provided by the first fueling system is increased so as to meet the requirement for increased knock resistance as the torque and speed of the engine are changed.   
     
     
         12 . The fuel management system of  claim 11  where the maximum knock free torque is increased relative to the maximum knock free torque if the direct injection occurred before the inlet valve was closed. 
     
     
         13 . The fuel management system of  claims 11  and  12  where when both fueling systems are used combustion stability is greater than when the first fueling system is used alone. 
     
     
         14 . The fuel management system of  claim 11  where spark retard is decreased when the fraction of fuel delivered to the engine cylinder from the first fueling system is increased. 
     
     
         15 . The fuel management system of  claim 11  where closed loop control using a knock detector is employed. 
     
     
         16 . The fuel management system of  claim 15  where the fuel management system minimizes the fraction of fuel delivered to the engine cylinder from the first fueling system as the torque is increased. 
     
     
         17 . The fuel management system of  claim 16  where open loop control and a microprocessor are employed. 
     
     
         18 . The fuel management system of  claim 11  where gasoline is introduced into the engine. 
     
     
         19 . The fuel management system of  claim 11  where ethanol is introduced into the engine. 
     
     
         20 . The fuel management system of  claim 11  where the second fueling system introduces fuel by port fuel injection. 
     
     
         21 . The fuel management system of  claim 11  where the second fueling system introduces fuel into the manifold.