Engine timing apparatus for use in testing

Abstract

Engine timing apparatus includes a timing light, cylinder clock signal circuitry, a cylinder counter, a cylinder comparator, first, second and third timers, a trigger pulse generator, operator control buttons, and a computer. The first timer measures a first time period between firing of the No. 1 cylinder, and the second timer measures a second time period between firing of the cylinder preceding No. 1 and the firing of the No. 1 cylinder. The computer derives from the first and second time periods a first digital value which represents the angular degrees from firing of the cylinder preceding No. 1 to firing of the No. 1 cylinder. Each time the comparator output signal is produced, the third timer initiates an adjustable time period, and the trigger pulse generator triggers the timing light at the end of the adjustable time period. The operator control buttons include buttons which cause a second digital value to be increased or decreased. The computer uses the first and second digital values and the measured first time period to control the adjustable time period of the third timer. When the operator has varied the second digital value so that the flashing of the timing light corresponds to top dead center of the No. 1 cylinder, the computer causes an angular value to be displayed which represents the angular relationship between firing of the igniter and top dead center of the No. 1 cylinder.