With the torque request signal from the PHEV-ECU, the engine-ECU controls the throttle valve opening degree. It can adapt to the designated opening degree to which various adjustments are applied, based on the predetermined basic opening degree.

When engine is started

Engine-ECU adds various compensations to the target opening angle that are set based on the engine coolant temperature, so that the air volume is optimum for starting.

When engine is driven

Based on the torque request signal from the PHEV-ECU and the engine rotational speed, the each adjustment is applied to the predetermined opening degree. The throttle valve opening degree is controlled.

List of main compensations for throttle valve opening angle and idle speed control

Stable idle compensation (immediately after start)
In order to stabilize idle speed immediately after start, target opening angle is kept big and then gradually reduced. Compensation values are set based on the engine coolant temperature.
Barometric pressure compensation
At high altitudes barometric pressure is less and the intake air density is low. So, the target opening angle is compensated based on barometric pressure.
Engine coolant temperature compensation
Compensation is made according to the engine coolant temperature. The lower the engine coolant temperature the greater the throttle valve opening angle.

Initialize control

After ignition switch turns OFF, engine-ECU drives the throttle valve from fully closed position to fully open position and records the fully closed/open studied value of the throttle position sensor (main and sub) output signals. The recorded studied values are used as studied value compensation for compensating basic target opening angle when the engine is started next.