Warning: This function is for experienced tuners only and requires knowledge of closed loop control systems.
Closed Loop Idle Speed Control provides a more complex idle control system that when correctly setup produces a very stable and repeatable idle speed control. Closed Loop ISC continuously looks at the current engine speed and compares it with the desired idle speed (Idle Target) so that adjustments can automatically be made. Closed Loop ISC control requires that all lockout conditions are met before it will automatically adjust idle speed.
This table allows the user to specify what the base idle position will based on up to two parameters. By default the table is created with one axis and uses ECT as the parameter on that axis but this can be customised through the right click -> Axis Setup option or the shortcut key 'X'.
The value in the table is the percentage of how open the ISC actuator is from 0% to 100%. When using an E-Throttle you would normally only use a very small portion of this range as it represents the full throttle plate movement range.
Values higher than the Max Clamp and lower than the Min Clamp can be entered into the table but the actuator will still be clamped between these values.
The various offsets listed in Idle Correction Settings will add to this base position giving the final position of the actuator before the closed loop corrections are added.
Idle Target RPM Position Table
This table sets the target (desired) idle RPM for a given engine state, the table has two axes and is customisable using the normal right click -> Axis Setup option or the shortcut key 'X'.
Closed Loop Specific Corrections
These corrections are specific only to Closed Loop idle speed control.
·Deadband - the rpm range around the target rpm in which the idle is considered to be on target. This zone spans 1/2 the Deadband value in either direction of the rpm target value.
·Integral Gain - Gain with respect to the accumulated offset between actual value and target value, this is the gain that corrects the idle speed when it varies from the target.
Closed Loop ISC Control Setup Procedure
The following checks should be made before attempting to setup the idle control system:
·Ensure the idle control valve/stepper/E-Throttle is correctly plumbed and wired to an auxiliary output/s (note that some actuator types require specific output pins). If using Electronic Throttle control ensure that this is properly configured.
·Ensure that the Actuator's settings have been setup correctly.
·Adjust the value in the Idle Base Position Table for the current engine coolant temperature, Changing the value should result in a change in engine speed, increasing the value should increase engine speed and vice versa. The idle actuator should be able to adjust engine speed from at least 300 RPM above and below the desired idle speed at all engine temperatures. Note that when using Ethrottle a very small change in throttle position will result in a large variation in engine speed.
Testing has proved that a very reliable idle control can be achieved by applying closed loop compensation to a correctly setup Open Loop Idle Speed Controller.
The following procedure describes the recommended method of configuring closed loop idle control
1.Perform the Open Loop ISC Control Setup Procedure first (DO NOT skip this step!)
2.Set Idle Speed Mode to Closed Loop.
3.Set all Idle Up values to zero (Engine Fan Idle Up, Power Steer Idle Up and Gear/Drive Idle Up).
4.Set Integral Gain to 1.
5.Locate the Idle Position and Idle Target runtime values under the Aux Functions tab (R or F12).
6.Enter the desired idle target RPM values in the Idle RPM Table.
7.Starting with a cold engine, start the engine.
8.As engine coolant temperature increases, for each cell in the Idle Base Position Table:
·Allow idle RPM to stabilise at that temperature.
·Read the Idle Position runtime value. This is the position the closed loop system has determined is required to achieve the target idle RPM.
·Enter the value back into the appropriate cell in the Idle Base Position Table.
9.Fill in the cells in the Idle Base Position Table above and below the engine coolant temperature operating range with suitable values.
10.OK, at this stage the basic Closed Loop ISC setup has been completed. It is now time to tune the closed loop system for optimum response to changes in engine load.
11.Tune Integral Gain to obtain the best response. A good test is how well the engine returns to idle after a free rev
Other Hints for Idle Control Setup
·When using an ISC Stepper Motor, start with lower numbers in the Idle Base Position Table (eg 50) rather than higher numbers. That will prevent the stepper motor from winding out too far during reset and bottoming out (bottom out causes loss of a known position). This will cause a higher idle RPM, but ensure that the stepper is in a known position while setting up idle speed control. Also set up in open loop mode first.
·When using an ISC Stepper Motor, it may be necessary to cycle the key a few times before a consistent stepper position is found.
·Keep ignition values similar around the low RPM/load cells. Ignition timing has a significant effect on idle speed and having large changes between ignition cells can cause an oscillating (hunting) closed loop idle. Ignition timing can also be used to obtain a higher/lower idle RPM if required.
Click HERE to return to the Idle Speed Control Page