Abstract: An electronic ignition system is disclosed for controlling as a function of at least one selected engine parameter the ignition or spark instants of an internal combustion engine having at least one cylinder with a piston and a rotatable crankshaft coupled to the piston to be rotatably driven as combustions occur within the cylinder at spark instant. The crankshaft has at least one reference position defining a positional relationship of the crankshaft to the cylinder. The electronic ignition system comprises a rotor fixed to rotate with the crankshaft and having a plurality of reference indicia thereon positionally related with respect to the reference position. The reference indicia are disposed at points equally spaced from each other by a predetermined arc of crankshaft rotation about the rotor. At least one of the points has a missing indicium and is disposed in a predetermined relation to the reference position of the crankshaft.

Abstract: An electronic ignition system is disclosed for controlling as a function of at least one selected engine parameter the ignition or spark instants of an internal combustion engine having at least one cylinder with a piston and a rotatable crankshaft coupled to the piston to be rotatably driven as combustions occur within the cylinder at spark instant. The crankshaft has at least one reference position defining a positional relationship of the crankshaft to the cylinder. The electronic ignition system comprises a rotor fixed to rotate with the crankshaft and having a plurality of reference indicia thereon positionally related with respect to the reference position. The reference indicia are disposed at points equally spaced from each other by a predetermined arc of crankshaft rotation about the rotor. At least one of the points has a missing indicium and is disposed in a predetermined relation to the reference position of the crankshaft.