Engine and Emission Control System Description

Ignition Timing Control
ENGINE AND EMISSION CONTROL SYSTEM DESCRIPTION

Ignition Timing Control (Cont'd)



SYSTEM DESCRIPTION The ignition timing is controlled by the E.C.U. in order to maintain the best air-fuel ratio in response to every running condition of the engine. The ignition timing data is stored in the ROM located in the E.C.U., in the form of the map shown below. The E.C.U. detects information such as the injection pulse width and crank angle sensor signal which varies every moment. Then responding to this information, ignition signals are transmitted to the power transistor. e.g. N: 1,800 rpm, Tp: 1.50 msec A ~B.T.D.C.
In addition to this, 1 At starting
2 During warm -up
3 At idle
4 At low battery voltage
5 During swirl control valve operates
6 Hot engine operation
7 At acceleration
8 When intake air temperature is extremely high
the ignition timing is revised by the E.C.U. according to the other data stored in the ROM.
ENGINE AND EMISSION CONTROL SYSTEM DESCRIPTION


Swirl Control Valve (S.C.V.) Control






SYSTEM DESCRIPTION This system has a swirl control valve (S.C.V.) in the intake passage of each cylinder. While idling the S.C.V. closes. Thus the velocity of the air in the intake passage increases, promoting the vaporization of the fuel and producing a swirl in the combustion chamber. Because of this operation, this system tends to increase the burning speed of the gas mixture, improve fuel consumption, and increase the stability in running conditions. The solenoid valve controls S.C.V.'s shut/open condition. This solenoid valve is operated by the E.C.U.
ENGINE AND EMISSION CONTROL SYSTEM DESCRIPTION


Fail-safe System



AIR FLOW METER MALFUNCTION If the air flow meter output voltage is above or below the specified value, the E.C.U. senses an air flow meter malfunction. In case of a malfunction, the throttle sensor substitutes for the air flow meter. Though air flow meter is malfunctioning, it is possible to drive the vehicle and start the engine. But engine speed will not rise more than 2,400 rpm in order to inform the driver of fail-safe system operation while driving.



ENGINE TEMPERATURE SENSOR MALFUNCTION When engine temperature sensor output voltage is below or above the specified value, water temperature is fixed at the preset value as follows:
THROTTLE SENSOR MALFUNCTION When throttle sensor output voltage is below or above the specified value, throttle sensor output is fixed at the preset value.

AIR TEMPERATURE SENSOR MALFUNCTION When air temperature sensor is below or above the specified value, air temperature value is fixed at the preset value [20~C (68~F)].