Cylinder compression detection

An engine cylinder compression detection apparatus for a spark-ignited internal combustion engine having a plurality of combustion sequence phase-opposed pairs of combustion cylinders, and a distributorless ignition system including a respective ignition coil for each one of said plurality of combustion sequence phase-opposed pairs of combustion cylinders for providing phase opposed spark events across sparking means disposed in the respective combustion sequence phase-opposed pair of combustion cylinders, comprising:

• sensing means for providing a composite signal representing polarity and magnitude of respective phase opposed spark events in each of said plurality of combustion sequence phase-opposed pairs of combustion cylinders;
• and,
• detection means responsive to said composite signal for providing a first diagnostic signal when said composite signal indicates a first polarity and magnitude relationship of phase opposed spark events across sparking means disposed in the respective combustion sequence phase-opposed pair of combustion cylinders and a second diagnostic signal when said composite signal indicates a second polarity and magnitude relationship of phase opposed spark events across sparking means disposed in the respective combustion sequence phase-opposed pair of combustion cylinders, wherein one of said first and second diagnostic signals indicates compression in one of the combustion cylinders of the respective combustion sequence phase-opposed cylinder pair and the other of said first and second diagnostic signals indicates compression in the other one of the combustion cylinders of the respective combustion sequence phase-opposed cylinder pair.

An engine cylinder compression detection apparatus for a spark-ignited internal combustion engine having a pair of combustion cylinders operating in combustion sequence phase opposition and a distributorless ignition system, comprising:

• an ignition coil including primary and secondary windings, the secondary winding having a first end coupled by a first conductor to a first spark plug disposed in one or said pair of cylinders and a second end coupled by a second conductor to a second spark plug disposed in the other of said pair of cylinders;
• a sense line capacitively coupled to the first and second conductors for producing a transient voltage signal in response to a spark discharge of either of said spark plugs characterized by a first polarity when the first spark plug discharges and a second polarity when the second park plug discharges, said transient voltage signal further characterized by a first magnitude less than a predetermined magnitude if the one of said pair of cylinders corresponding to the one of the first and second spark plugs discharging is exhausting and a second magnitude greater than the predetermined magnitude if the one of said pair of cylinders corresponding to the one of the first and second spark plugs discharging is compressing;
• and
• bi-stable detection means coupled to said sense line for establishing a first output state only when said transient voltage signal of said first polarity is characterized by said second magnitude and a second output state only when said transient voltage signal of said second polarity is characterized by said second magnitude.