Idle Control

Idle Control

Idle Control

The Idle Control function allows your ECU to control the engine idle speed. There are multiple ways this is achieved with either Drive-By-Wire (DBW) control, a Bypass Air Control (BAC) solenoid with either two or 3 wire types, or via a Stepper Motor system. The purpose is to allow a controlled amount of additional air to enter the engine to increase or decrease engine torque, which in turn will raise or lower the engine speed.



Output

Control Method

Select the type of control method used for idle control.
DBW - The DBW Throttle is to be used for idle control. Only select this if a DBW Throttle has been correct configured. The DBW Throttle will be opened and closed by the ECU to control the amount of additional air.
BAC Two Wire - A two wire solenoid is being used for Idle Control. This will use a varying duty cycle signal, similar to a fuel injector, to control the amount of additional air. Typically zero duty will fully close the valve, and full duty will fully open the valve.
BAC Three Wire - A three wire solenoid is being used for Idle Control. This will actually use two solenoids that share a common 12V+ power supply. Typically one solenoid is used to increase air flow from a middle position, and the other solenoid is used to decrease air flow from a middle position. Without any connection these solenoids will typically flow half of the available amount of air.
Ignition Only - Suitable for vehicles without a Drive By Wire throttle or Idle Air Control Valve.
Stepper Motor (Absolute) - A stepper motor is to be used for Idle Control. In Absolute mode the Idle Control will calibrate the stepper motor to find its position by winding in the motor by the amount set in the Full Range, and then winding out to the Base Duty amount. For a Stepper Motor the Duty refers to a percentage amount of the Range. The ECU will then control the Stepper Motor by following commanded values in the Idle Control base tables.
Stepper Motor (Relative) - A stepper motor is to be used for Idle Control. In Relative mode the Idle Control will simply open or close the idle valve depending on whether it is above or below the target, and not follow any Idle Control base tables. Long Term control is not available with this Signal Type.

Output Max

The maximum amount of Duty Cycle that can be output by the Idle Control.

Frequency

Available when BAC Two Wire or BAC Three Wire is selected as the Signal Type. Sets the frequency at which the solenoid is to be pulsed.

BAC Type

Only available when BAC Three Wire is selected as the Signal Type. This configures the type of solenoid control that is to be used.
Uni-Directional - Both outputs will have the same duty. i.e. When the Main is 25% the Slave is 25%.
Complementary - When one output wire is increasing duty the other will be inverted and decreasing duty. i.e. When the Main is 25% the Slave is 75%.
Bi Directional - One solenoid controls 0-50% of the valve opening, the other controls 50% to 100% of the valve opening. The solenoid itself defaults to 50% open when no connection at all is present.

DBW Max Position

Available only when DBW is selected as the Signal Type. This sets the amount of throttle percentage that will be used when 100% Duty is commanded by the Idle Control. 

Stepper Max Speed 

Sets the maximum speed at which the ECU drives the stepper motor.

Stepper Range 

Sets the step range of the stepper motor idle motor used.

Stepper Invert 

Inverts the output direction of the stepper motor controller.

Stepper Motor Calibration 

Selects the method in which the stepper motor will calibrate. Normal Calibration fully closes the stepper motor during calibration. If the engine is started while the stepper motor is still calibrating, the engine will initially idle low. Reverse Calibration fully opens the stepper motor during calibration. If the engine is started while the stepper motor is still calibrating, the engine will initially idle high.

Controller

Mode

Choose from Open or Closed Loop mode. Closed Loop allows the ECU to make adjustments to the idle output to keep the idle on Target. Open Loop requires the tuner to adjust the idle output manually and the ECU will not make any adjustments from this.

PID Scaler

Allows for quick changes to the Proportional, Integral, and Derivative tables for testing purposes. A setting of 100% gives normal PID control.

RPM Rate Lower Limit

Closed Loop control will only be active when the RPM is falling at a rate less than this amount. This setting is to prevent the idle control from making adjustments to try and reach the Target when the Idle is not yet stable by not operating the Proportional and Integral components. Setting this closer to zero will cause the controller to wait for a steadier RPM before starting the controller. Setting this further from zero will start the controller earlier.

RPM Rate Upper Limit

Closed Loop control will only be active when the RPM is rising at the rate less than this amount. This setting is to prevent the idle control from making adjustments to try and reach the Target when the Idle is not yet stable by not operating the Proportional and Integral components. Setting this closer to zero will cause the controller to wait for a steadier RPM before starting the controller. Setting this further from zero will start the controller earlier.

Decel Fuel Cut Restore

Decel Cut will not be active when the RPM is lower than this amount above the idle Target RPM. This is to ensure a Decel Cut RPM value cannot be set lower than the idle Target RPM.

Decel Offset

Sets the amount of extra duty to be added to the Base Duty when the throttle has been closed. This is used to help to catch the engine when the RPM is falling to prevent RPM dropping below the Target RPM. When normal idle conditions are met, this amount will decay back to normal over a period of time set in the Decel Offset Decay Time.

Decel Offset Decay Time

The amount of time for the Decel Offset will decay back to normal operation. 

Stall Offset

When RPM falls this amount below the Target RPM the idle output will be set to 100% to help save an engine from stalling. When RPM is above this normal operation will resume.

Close Idle Valve On Boost

When enabled will set the Duty Cycle to 0% when there is positive boost pressure. Used when an idle control valve is not connected back into the pressure feed before the throttle body. i.e. it would cause a boost leak if the valve is not closed.

Max Vehicle Speed

Active only when a Vehicle Speed Sensor is enabled. Sets the vehicle speed that the vehicle must be below before closed loop control of idle can commence. This is to let the ECU know that the engine is at idle and is not being driven, and prevents possible stalling on long and slow deceleration. Although not required, it is highly recommended that a vehicle speed sensor is used when Idle Control is active. 

Functions

Throttle Follower (Dashpot) Enable

The Throttle Follower smooths the transition from open throttle to closed throttle. This is done by increasing the idle output based on the amount of rpm and load the engine is using and decaying it away as the throttle is closed. Ticking this box enables the Throttle Follower. This activates the Throttle Follower Target and Throttle Follower Decay Tables.


    • Related Articles

    • Idle Control Wiring

      This article explains the most common types of idle air control valves and how to wire them up using a Haltech Nexus or Elite ECU: Bypass Air Control (BAC) Two Wire This type of idle valve is the simplest to wire up, being a solenoid with just two ...

    • Idle Control Tuning

      Idle Control is used to hold the RPM steady while off the throttle. To do this the ECU needs to be controlling a device that regulates air flow into the engine. This can be via DBW throttle control, a 2 or 3 wire solenoid, or a stepper motor valve. ...

    • Tuning For Idle (ignition)

      Typical idle speeds usually sit between 500 RPM and 1000 RPM. In order to assist the idle control mechanism to achieve a steady engine speed, it is advisable to ensure that the ignition advance at the idle loads between 500 and 1000 RPM are similar, ...

    • Engine Configuration

      Engine Configuration The Engine Configuration node contains basic configuration information about your engine. Engine Information Engine Capacity The Displacement of the engine. The units for Displacement are selected in the NSP software under ...

    • Traction Control User's Guide

      Introduction This is a guide on how to use the Traction Control Function for typical street or mild racing use.  This guide will focus on the newer Percentage Cut system found on Nexus VCU and Elite ECU with firmware v2.34-onwards.  The Percentage ...