Individual cylinder spark deration

Claim 1

In a spark ignited internal combustion engine, means responsive to the occurrence of engine knock comprising: means for sensing engine knock and converting same into a corresponding electrical knock signal; means for sensing engine speed and converting same into a corresponding electrical pulsed signal with leading and trailing edges for each pulse; storage means for storing a spark advance derate value for each cylinder and for storing a predetermined spark advance relationship; comparing means to discriminate between the leading and trailing edges of the pulses; means to determine the current cylinder number and the preceding cylinder number in the firing order; means to calculate spark advance according to the predetermined spark advance relationship for each cylinder utilizing the corresponding spark derate value if the pulse is at the leading edge; means for firing the spark to the corresponding cylinder using the calculated spark advance value; means for defining a knock zone for each cylinder; means for detecting the presence of a knock signal within the knock zone; means for deciding whether a knock signal was present within the knock zone for the preceding cylinder number; and means for increasing the spark advance derate value for the preceding cylinder and updating the stored value for the corresponding cylinder if the knock signal was present during the knock zone; the means responsive to the occurrence of engine knock further comprising means to decay a cylinder's stored spark advance derate value as a function of time.