Spark timing control system for internal combustion engine

Abstract

The occurrence times of discharges of a multi-cylinder internal combustion engine of an automotive vehicle having a transmission and sources for deriving signals indicative of: (a) the engine being cranked or operating normally, (b) the transmission being in high or low gear, (c) engine speed, and (d) the values of parameters determining engine load are controlled by a computer responsive to the signals. The computer includes a read only memory having tables for storing signals with values indicative of spark advance and dwell angle as functions of engine load and engine speed for the engine being cranked, operating normally, the transmission being in high and low gear. The computer responds to the signals of the sources for selecting from the tables stored signals having values indicative of spark advance and dwell angle corresponding with the conditions indicated by signals (a), (b), (c) and (d). A spark control circuit responds to the signals having values indicative of spark advance and dwell angle to control the occurrence times of sparking for each cylinder of the engine. The same type of computer is susceptible to use for vehicles having different spark advance and dwell angle characteristics as functions of engine speed and engine load. The tables are for plural vehicle types having the different characteristics. Switches selectively enable signals of the tables associated with only one of the vehicle types to be coupled to the computer.