Control method for protecting an IC engine during extended heavy loading

Claim 1

A control system for a spark ignition internal combustion engine including spark timing means for initiating engine combustion events in accordance with a spark timing signal, and fuel delivery control means for delivering fuel to the engine, the engine having a tuning range of speeds during which there is increased tendency for engine knock and/or preignition to occur, the control system comprising: optimum performance control means effective during engine operation for which engine performance concerns predominate for (1) supplying the spark timing means with a spark timing signal corresponding to an empirically determined MBT setting for substantially maximum engine torque and (2) causing the fuel delivery control means to deliver an extra amount of fuel to the engine if the engine speed is in said tuning range, permitting continued safe operation with the spark timing means controlled to said MBT setting; reduced performance control means activateable during engine operation for which engine protection concerns predominate for overriding said optimum performance control means by supplying the spark timing means with a spark timing signal which progressively retards the spark timing from the MBT setting to a predetermined value at which engine operation may be continued at a reduced performance level without incurring engine damage; timing means for identifying periods of heavy engine loading above a threshold engine speed and load, and for integrating such periods over time to define cumulative heavy loading indication; and engine protection means effective when the cumulative heavy loading indication exceeds a reference time for activating the reduced performance control means to protect the engine from damage.