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Idle

Idle RPM

The table sets the desired idle speed depending on the engine temperature.

RPM when moving

Allows you to increase the idle RPM when the vehicle speed is not zero.

Min. position

Sets the minimum valve position. Should be adjusted to 100-200 rpm below idle rpm.

After start add

Sets the additive to the minimum position, which will work after start. It affects RPM rise and drop after the start.

Pick up

Pick-up RPM - the recommended value is 200. This is the RPM above idle, at which the regulator should hold the RPM.

Pickup Percentage is the position additive that is needed to raise the RPM by the specified pickup RPM.

For example:

  • Idle target = 800, position is 25%.
  • Pick-up revs = 200.
  • We increase the revs by 200, now the RPM is 1000, position is 28%
  • We calculate the percentage of pickup: 28-25 = 3%

Test

Raises the target RPM by the pickup value for a couple of seconds, then returns it back. Convenient for tuning the PID controller.

Manual control

Allows you to manually set the IAC position. When set to zero, manual control is disabled.

Stabilization by ignition angle

Sets the stabilization levels by the RPM deviation and by the crankshaft acceleration.

Idle cutoff

Fuel cutoff parameters when pedal released when driving in gear

  • Off - RPM, above which the cut-off is triggered, the injection is turned off
  • On - RPM below which fuel supply is resumed, injection is switched on
  • Speed ​​- The cutoff is triggered above the specified speed. Designed for smooth driving at low speed.
  • Delay - This is the time delay between releasing the accelerator pedal and cutting off the fuel. Adjusts separately for low and high rpm.

Corrections

Here, the corrections are set when the air conditioner / automatic transmission is turned on / off to eliminate idle speed deviations when a large load is turned on.

For the switched on air conditioner, idle speed is set separately

The On and Off parameters include the IAC position correction. The values ​​are selected so that turning on and off the air conditioner was not perceptible.

Stepper motor

Here you can turn on the stepper IAC mode. In this case, the ABCD outputs are used to connect the IAC stepper motor.

Number of steps

Sets the number of steps of the stepper. It is necessary to set the minimum number of steps required for regulation in order to speed up initialization.

On power-up, the stepper motor should turn to the closed position, and then return to the working position. The fewer the number of steps, the faster it will finish. A starter lock relay can be installed to disable the starter until the stepper motor is initialized.

Tuning method

Setting the min. position

The minimum position sets the threshold below which the IAC cannot close.

  1. On a cold machine (temperature below 30C), manually set the speed to 100-200 rpm lower than the idle speed.
  2. Write the position of the IAC to the "min. Position at 30C"
  3. Warm up the car to 90g and manually set the speed to 100-200 rpm lower than the idle speed.
  4. Write the position of the IAC to the "min. Position at 70C"
  5. If you notice that during driving, the IAC stucks into the min. Position, and the revs are still higher than the target, you need to reduce the min. position to give the regulator more room to adjust.

Info

Some IACs (for example, Audi) have an emergency position: in the zero position, the valve is slightly open. Then, when the position is increased, the valve closes, and from about 30-40% it opens again. This is done so that the engine does not stall in the absence of a control signal.

Setting the PID coefficients

  1. Warm up the engine
  2. Set the cut-off idle speed = 6000
  3. Set Kp = 0 Ki = 5 Kd = 0

Ki setting

This is the most important coefficient. It sets the speed of adjusting the revs with small deviations. For example, you turned on the air conditioner, the rpm dropped, and then recovered. The speed with which the regulator will raise the revs is set by Ki.

  1. Set 800 in the target RPM table and wait for the RPM to stabilize
  2. Set 1200 in the target RPM table and wait for the RPM to stabilize.
  3. Repeat steps 1-2 and adjust the Ki regulator to set the speed in 3-4 seconds.

Kp setting

This coefficient increase the response of the regulator at large deviations.

  1. Set 800 in the target RPM table and wait for the RPM to stabilize
  2. Set 2000 in the target RPM table and wait for the RPM to stabilize.
  3. Repeat steps 1-2 and increase Кр until RPM unstability/overshoot is reached. Then decrease the obtained value by half.

Kd setting

Kd limits RPM decreasing speed. This coefficient has little effect on the operation of the IAC, but it can cause instability. Increase Кd until RPM unstability/overshoot is reached. Then decrease the obtained value by half.

Setting up the pickup

When the pedal is released, the IAC stabilize RPM above target, and then gradually drops it to the target. The higher the value, the higher the pickup.

  1. Set proper idle cutoff values.
  2. Step on the gas and quickly release the pedal
  3. Set the pickup so that the revs stabilize at pickup RPM for 0.5sec, and then drops smoothly to the target, and never falls below target.