AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 152)

Page 152 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
A/C On Delay, Units: Seconds - Description: The time between when the A/C request is
switched ON and the A/C compressor is turned ON. Used to open the idle motor slightly before
the increased load from the A/C compressor to counter-act idle surge.
A/C Idle Load Comp, Units: Idle % Description: Amount of extra duty required to maintain the
existing target RPM when the A/C compressor is enabled. The value can be positive or negative
depending on how the idle air control motor responds. A typical value is (+/-) 5. Encourages a
stable idle when the A/C is switched ON and is used in conjunction with the A/C On Delay
option.
Hi Idle RPM Offset, Units: RPM - Description: Additional RPM added to the idle target when in
the "high idle" condition. Typically used for engine deceleration to help prevent engine stalling.
Hi Idle Above VSS, Units: Vehicle Speed. Description: When above this speed, the high idle
condition will be maintained indefinitely. The vehicle speed sensor must be set up for this
function to work. Typically used for engine deceleration to help prevent engine stalling.
Hi Idle Wait Time, Units: Seconds - Description: Counter limits how long the high idle offset
conditions will be met once the idle conditions are met. Typically used for engine deceleration to
help prevent engine stalling.
Idle FB Below rpm, Units: RPM Description: Maximum RPM threshold for closed loop idle
feedback. A typical value is 1700 RPM. Stalling can occur if this RPM value is too high. This
stalling is typically caused from driving slow enough to never exit the closed loop idle condition.
The idle air control motor will completely close in attempt to bring the idle to the target value and
cannot react and open fast enough if the user lets off the throttle for an idle state. A steady
"open loop" high idle can occur if this RPM value is too low. This is caused from the base idle
speed (Idle% vs Target table) never dropping below the Idle FB Below rpm condition.
Idle FB Above rpm, Units: RPM Description: Minimum RPM for closed loop idle feedback. The
lowest idle speed possible that should mimic the Crank Exit RPM. A typical value is 400 RPM.
Open loop idling can occur if this value is too large where the idle air control motor does not
respond. If the Engine RPM goes below this value, idling will be solely dependent on the Ign
Timing and Fuel Inj Base Pulse parameters.
Idle PW Frequency, Units: uS, Description: For pulse width idle air control motors only. Defined
as a “Frequency” but as specified, the value is actually a “period”. Frequency and Period are
related by the equation:
Frequency (Hz) = 1 / Period (seconds)
One uS or microsecond = 1 x 10 -6 seconds
Sets a frequency that is specific to the idle pulse width motor being used. If the idle air control
motor is noisy or has a lazy response, the frequency should be changed. Typical frequency
values for most OEM idle air control valves are 100
– 300 Hz.