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

Page 161

Tuning Guide

155

Advanced Setup:

Idle Proportional Gain:
Proportional control is a pure gain adjustment acting on the magnitude of the target error
to provide the system response. The advantage of a proportional-only control is it can
respond quickly to large errors; when the error is large the proportional response will be
large. The disadvantage of proportional gain for idle control is the proportional response
will decrease to zero as the engine speed gets closer to the idle target RPM, and this
tends to result in 'hunting' or fluctuations in engine speed. It is recommended to begin
tuning idle feedback with this value set to zero or very low values. If the system responds
too slowly to quick disturbances, increase this value slightly.
Min value = 0.000, Max value = 1.000

Idle Integral Gain:
Integral control uses an integrator or 'accumulator' method, essentially checking if the
target error is positive or negative and then taking one step up or one step down every
400ms to reduce the target error. The advantage of integral response for idle control is
the idle airflow will be slowly and smoothly adjusted until the engine speed reaches the
target, and then remain at whatever feedback value reached the target. Note: Although
Integral gain is less likely to cause hunting or fluctuations than Proportional or Derivative
gains, excessively high Integral values will take steps that are too large which can result in
instability.
Min value = 0.000, Max value = 1.000

Idle Derivative Gain:
The derivative term adjusts the feedback based on the rate of change of the target error.
Derivative control is used to reduce the magnitude of the overshoot produced by the
Proportional component and improve the combined controller-process stability. Note: for
most setups, it is recommended to leave the Derivative gain set to zero. For tuners who
are very familiar with PID feedback and are observing a situation that could be alleviated
by adjusting Derivative gain, it is recommended to use the Idle_Decel table rather than the
Derivative gain.
Min value = 0.000, Max value = 1.000

Idle FB Deadband:
The idle airflow valve is not the only factor that can influence engine speed and idle
stability. In some cases, changing idle airflow in response to the engine's natural instability
will cause the engine to fluctuate even more than if the idle valve were locked at a constant
position. The Idle feedback deadband range defines an operating window where the
engine speed is considered to be 'close enough' to the idle target and the IdleFB value
should be paused. This deadband range should be larger for engines that do not idle
smoothly, such as setups including aggressive camshafts, lightweight flywheels, or fuel
injectors that flow inconsistently when operated at small pulsewidths.