is shown in fig1 engine 70 shown is a spark ignition engine with spark plugs 74 installed into engine 70 the invention may also apply to a compression ignition engine which does not rely on spark plugs for ignition engine 70 is supplied fuel directly into the combustion chamber through injectors 72 as would be the case in a direct injection gasoline or diesel engine fuel injectors 72 could be situated alternatively near the intake ports to the combustion chamber engine 70 is provided with a cam phaser 34 which can alter the time at which the valves open and close relative to engine crankshaft rotation a more detailed description is provided below with reference to fig2 engine 70 is supplied fresh air through an inlet duct containing a throttle valve 78 the engine discharges gases into an exhaust duct 88 a portion of the exhaust gas stream may be routed back to the intake duct through exhaust gas recirculation egr valve 90 continuing with fig1 engine control unit ecu 18 has a microprocessor 50 called a central processing unit cpu in communication with memory management unit mmu 60 mmu 60 controls the movement of data among the various computer readable storage media and communicates data to and from cpu 50 the computer readable storage media preferably include volatile and nonvolatile storage in read only memory rom 58 random access memory ram 56 and keep alive memory kam 54 for example kam 54 may be used to store various operating variables while cpu 50 is powered down the computer readable storage.