An adaptive fuel limit function (52) for protecting an internal combustion
engine. The adaptive fuel limit function is a learning function responsive
to trends in an engine performance parameter such as compensated fuel
consumption per unit of power produced (62). The engine performance
parameter is processed through a low pass filter (64) to allow changes in
a fuel limit signal (54) in response to gradual changes in the fuel
demand, such as may be due to wear in the engine, while blocking changes
in the fuel limit signal in response to sudden changes in the fuel demand,
such as may be due to a cylinder failure. The difference between the input
and the output of the low pass filter may be processed to identify a
failure level (88) for providing an alarm function distinct from the
learning function.
