Open Loop Idle Speed Control provides a simple means of regulating idle speed. This mode of Idle Speed Control allows the tuner to set the Idle Speed Controllers position based on one or more engine parameters such as coolant temperature. While the Idle Base Position table only allows for control based on up to two parameters (one per axis), additional compensations can also be applied for loads that may become active at idle such as A/C compressors or engine fans.
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.
Open Loop ISC 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.
The following procedure provides a general method for setting up open loop idle speed control. This procedure assumes that an Idle solenoid or stepper has been correctly wired and configured and that the engine in its final state of tune.
1.Ensure Fuel Warm-up Enrichment has been tuned.
2.Set Idle Speed Mode to Open Loop.
3.Set all idle offsets to 0 (Engine Fan Offset, Initial Engine Fan Offset, Power Steer Offset, Gear/Drive Offset, Dashpot Offset and AC Offset Table).
4.Set the Min and Max Clamps to appropriate values for the actuator type.
5.Ensure the Idle Base Position Table axes are set up appropriately (We recommend using ECT on one of them).
6.Starting with a cold engine, start the engine.
7.As the engine warms up, adjust each cell in the Idle Base Position Table to achieve the required idle speed. Note that it may be necessary to adjust the Max Clamp and Min Clamp values during this procedure.
8.Fill in the cells above and below the engine coolant temperature operating range with suitable values.
9.With the engine at normal running temperature, individually switch on any loads that may be connected and adjust the appropriate Offset Adjustments to achieve the required idle speed with the load active.
10.Set the various Hold and Decay Time settings as appropriate to ensure the idle remains stable as these loads are switched on and off.
11.Set the Min Clamp value as follows:
·ISC Stepper - Set Min Clamp to the lowest value in the Idle Base Position Table less the sum of all Idle Up Adjustments. eg if the lowest table value is 40 and there are two idle up adjustments used with values of 2 and 6, then set Min Clamp to 40 - 8 = 32.
·ISC Solenoid - Set Min Clamp to the lowest value in the Idle Base Position Table .
·Electronic Throttle - Set the Min Clamp to the lowest value in the Idle Base Position Table .
12.Set the Max Clamp value as follows:
·ISC Stepper - Set Max Clamp to the highest value in the Idle Base Position Table .
·ISC Solenoid - Set Max Clamp to the highest value in the Idle Base Position Table plus the sum of all Idle Up Adjustments. eg if the highest table value is 79 and there are three idle up adjustments used with values of 3, 9 and 5 then set Max Clamp to 79 + 3 + 9 + 5 = 96.
·Electronic Throttle - Set the Max Clamp to the highest value in the Idle Base Position Table
13.Set the various idle Lockouts as appropriate to achieve smooth transitions into and out of idle with minimal undershoot and fast response.
Note: In open loop ISC modes the Idle RPM table has no affect on the control of the idle solenoid/stepper/e-throttle and is only visible when using Idle Ignition Control.