85 engine electrical.pdf - Vintage Snow

cENGINE ELECTRICALSystem III - Electronics OperationThe Electronic Control System is the mixture control part of the system. It uses sensor inputs to control the fuel/airratio. The illustration shows the components of the basic Electronic Control System.Sensors (Inputs)(Three Cylinder System Shown)Twins have 2 injectorsInjectors (Outputs)ECUDrop Resistorc(Type II Systems Only)In FromBatteryDL......,,.....-----IOutput 0 0SelectMonitorDOThe electronic control unit delivers a low voltage signal to each sensor. Depending on variations in airtemperature, throttle position, etc., each sensor will vary the amount of that signal passing through it to grounddepending on its position and temperature. The ECU reads the information and from that determines what theactual air temperature, throttle pOSition, etc. is. This information is then plotted on a map which ispre-programmed on the PROM (Programmable Read Only Memory) or "chip". Based on the two primary inputs;RPM (x) and throttle position (y), the ECU can select a specific injector open time (z). This value is the distancebetween the base plane and the map at the point where x and y cross. The value is converted to milliseconds andreferred to as pulse width.cSimulatedprommapPulse Width(in milliseconds)(z)oRPM(x)Throttle Position(y)4.498/94