Abstract: An engine timing apparatus comprises an ultrasonic transducer 8 which directs a pulsed ultrasonic beam into a cylinder and converts the reflected ultrasonic signals into electrical signals. A sample/hold circuit 67 samples this signal at a time after each pulse when signal reflected by a piston ring passing through the beam are expected. A microcomputer 65 detects changes in the level of the sampled signal caused by the piston rings as the crankshaft rotates, and receives signals from a transducer 71 indicating the crankshaft position to allow top dead center position to be found. The microcomputer receives signals from a microphone 51 directed at a fuel injector indicative of the onset of ignition and calculates the timing angle of the engine. The apparatus also calculates engine speed and detects piston slap.

Abstract: An engine timing apparatus comprises an ultrasonic transducer 8 which directs a pulsed ultrasonic beam into a cylinder and converts the reflected ultrasonic signals into electrical signals. A sample/hold circuit 67 samples this signal at a time after each pulse when signal reflected by a piston ring passing through the beam are expected. A microcomputer 65 detects changes in the level of the sampled signal caused by the piston rings as the crankshaft rotates, and receives signals from a transducer 71 indicating the crankshaft position to allow top dead center position to be found. The microcomputer receives signals from a microphone 51 directed at a fuel injector indicative of the onset of ignition and calculates the timing angle of the engine. The apparatus also calculates engine speed and detects piston slap.