Duty Cycle of an Idle Speed Control Valve
In the setting of an idle speed control valve, duty cycle is the ratio of the time the valve is open to the whole time of a single cycle. It is represented as a percentage of total ON time.
The ECU controls idle speed by adjusting the duty cycle of the signal to the idle air control valve. This valve permits air to bypass the throttle valve, altering the amount of air that enters the engine at idle.
How it Works?
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The ECU transmits a pulse-width modulated (PWM) signal to the idle air control valve.
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The duty cycle of this signal controls how long the valve remains open in each cycle.
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A larger duty cycle (e.g., 60%) means the valve is open for a longer period of each cycle, allowing more air bypass & improving idle speed.
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A reduced duty cycle (e.g., 40%) indicates the valve is open for a shorter period, allowing less air bypass & decreasing idle speed.
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The ECU regulates the duty cycle based on engine temperature, load, & throttle position to keep the appropriate idle speed. This enables for fine electronic control over idle air flow & engine speed.
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