AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual User Manual

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EFI Components

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The advantage of a step type IAC motor is that once the motor is in the proper location, no signal
or power is required to maintain this position. The only time action needs to be taken is when
changing the location of the motor. The downside is there is an uncertainty to where the motor is
at any given time. This can be overcome by routinely resetting the IAC motor to a known location.
With tuning, this is achieved by stepping the motor all the way to its limit. However, this may
damage the motor if not set correctly. This will reset the motor.

Stepper motors do not have a position sensor. The location at engine start has to be assumed
since there is no time for it to reset. Therefore, it must be parked in a known location when the
engine is turned OFF. Parking of the stepper motor is crucial. After the engine is shut off, the
Infinity keeps power to the main relay and then resets and parks the stepper motor. This takes
about 5–7 seconds and is usually unnoticed by the user.

The other major IAC system is a pulse width duty cycle valve, shown below. This system
regulates air bypass volume by utilizing a duty cycle controlled solenoid. This electric solenoid
controls an air valve which blocks passage of air from the intake pipe to the intake manifold.
Since this solenoid is incapable of flowing high air volume, a separate mechanical air valve is
typically used to perform cold fast idle. With this type system, the Infinity varies bypass airflow by
changing the duty ratio of the command signal to the IAC valve. By increasing the duty ratio, the
Infinity holds the air bypass valve open longer, causing an increase in idle speed.

The advantage of this type of IAC system is that it does not need to park and because it does not
take steps, the valve is always at a known position. The disadvantage of this type of IAC system
is that power is required to maintain idle unlike the stepper motor type. Pulse width idle air
control systems also require specific frequencies to operate.

For more information, go to

Idle

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