Checklist Idle Setup – MoTeC Technical Support

This guide shows the recommend method to configure Idle control system. Clicking each item (M1 Tune v1.5 only) will select the item and allow you to enter the required information. Once an item has been selected the help, for that item, can be displayed by hitting the F1 key.

The Idle system

The Idle system controls engine speed when the engine is under idle conditions. Engine speed is controlled by varying ignition timing and controlling the air mass flow through the engine.

Setup

Process the following steps in this order:

Confirm Ignition Timing Main has been calibrated with the best torque ignition timing in the engine operating area where idle control is supposed to operate.
If not already configured in the package, set all parameters and table values in Idle to the default values mentioned in their respective help texts. The engine does not need to run for this.
Set Idle Actuator Throttle Aim Maximum or Idle Actuator Solenoid Maximum / Idle Actuator Solenoid Minimum dependent on which system is in use (drive by wire throttle or idle solenoid).
Calibrate Idle Mass Flow Feed Forward Main as described in the help for that table.
Set Idle Mode to Enabled and optimise Idle Ignition Timing Limit Advance Control Proportional Gain and Idle Ignition Timing Limit Advance Control Integral Gain so that Idle Ignition Timing Limit Advance is stable around Idle Ignition Timing Limit Advance Target .
Check that Engine Speed tracks Idle Aim nicely after throttle tip-ins. Optimise Idle Aim Ramp Down to achieve this.
Check that Engine Speed is stable at Idle Aim when the throttle is not used. Optimise Idle Mass Flow Integral Gain and Idle Mass Flow Proportional Gain to achieve this.
After exiting idle control, check that Idle Throttle Pedal Offset is an average of the Throttle Position that ensued during idle.

For a detailed explanation of the idle control system see the following remarks and the help text on each item.

Idle control activation

Idle control activation happens in two phases:

When the idle activation conditions (described below) have been met ignition timing is progressively retarded towards Idle Ignition Timing Limit Advance Target at Idle Ignition Timing Limit Advance Ramp degrees per second. Note that Idle State still is Disabled in this condition.
Once Engine Speed falls below Idle Aim, Idle State becomes Enabled and the system begins closed loop control.

The idle activation conditions are:

Engine State must be Run.
Ignition Timing Mode must be Normal.
Idle Mode must be Enabled.
Throttle Pedal must be less than Idle Activate Throttle Pedal Threshold.
Idle Switch must be On if the switch is configured.
Throttle Aim State must be Idle or Pedal, or Throttle Pedal Sensor Diagnostic must be Not in Use.
Engine Overrun State is Disabled or Advance Ignition
No gear shift is in progress
Engine Speed is below Idle Aim + Idle Activate Engine Speed Margin

Idle control is deactivated when Throttle Pedal is greater than Idle Activate Throttle Pedal Threshold + Idle Activate Throttle Pedal Hysteresis. When using the Idle Actuator Stepper or Idle Actuator Solenoid, if Engine Speed is above Idle Aim by more than this value the idle system will also be disabled.

The target idle speed is set by the Idle Aim system. The primary influence on the target idle speed is the Idle Aim Main table. A number of compensations are provided to correct for external influences such as the air conditioner compressor. Idle Aim Ramp Down assists in bringing engine speed under control by smoothly reducing the target idle speed.

When closed loop control is active engine speed is controlled by two closely coupled control systems, Idle Ignition Timing Limit Advance and Idle Mass Flow.

Idle Ignition Timing Limit Advance

The Idle Ignition Timing Limit Advance system performs closed loop engine speed control by varying ignition timing. If Engine Speed falls below Idle Aim ignition timing is advanced. If Engine Speed rises above Idle Aim ignition timing is retarded.

In order for this control system to operate effectively Ignition Timing Main must be calibrated such that it contains the minimum advance for best torque (MBT) ignition timing values in the region where idle control will be active. This allows the idle system a torque margin to correct for engine speed fluctuations.

The following items affect the operation of the control system:

Idle Ignition Timing Limit Advance Target must be more retarded than the normal ignition timing.
Idle Ignition Timing Limit Advance Ramp must be non-zero.
Idle Ignition Timing Limit Advance Control Proportional Gain sets the proportional gain of the control system.
Idle Ignition Timing Limit Advance Control Integral Gain sets the integral gain of the control system.
Idle Ignition Timing Limit Advance Minimum sets the retard limit for the control system.

If the activation conditions for idle control (described above) are no longer met ignition timing is advanced at Idle Ignition Timing Limit Advance Ramp degrees per second until normal ignition timing is reached.

Ignition Timing State will be Idle when the Idle Ignition Timing Limit Advance system is controlling ignition timing.

Idle Mass Flow

The Idle Mass Flow system controls the air mass flow through the engine by means of a PI controller. The correct mass flow has been reached when Idle Ignition Timing Limit Advance is equal to Idle Ignition Timing Limit Advance Target.

The result of the Idle Mass Flow system is a ratio from 0% to 100%. This ratio is translated into a real request by using an idle actuator.

The following items affect the operation of the control system:

Idle Mass Flow Feed Forward Main sets the open loop component of the control system.
Idle Mass Flow Integral Gain sets the integral gain of the control system.
Idle Mass Flow Integral Minimum sets the minimum integral clamp of the control system.
Idle Mass Flow Integral Maximum sets the maximum integral clamp of the control system.
Idle Mass Flow Integral Rate sets the integral rate limit of the control system.
Idle Mass Flow Proportional Gain sets the proportional gain of the control system.

When Idle State is Disabled the proportional part and the integral part of the controller are disabled but Idle Mass Flow Feed Forward is still effective. This provides a minimum aim position for a throttle servo control or a solenoid air bypass valve and is also used do define their position during cranking. See also Engine Crank Idle Mass Flow.

Idle Actuator Throttle Aim

The Idle Actuator Throttle Aim system converts an Idle Mass Flow request into a throttle aim usable by a throttle servo system. This is achieved by scaling the mass flow request by Idle Actuator Throttle Aim Maximum.

0% results in a throttle aim of 0%.
100% results in a throttle aim of Idle Actuator Throttle Aim Maximum.

To maintain an operating range for the idle control it is important that Idle Actuator Throttle Aim Maximum exceeds the throttle aim values that are usually effective during idle.

Idle Actuator Solenoid

The Idle Actuator Solenoid system converts an Idle Mass Flow request into a duty cycle suitable for an air bypass solenoid. This is achieved by scaling the mass flow request such that:

An Idle Mass Flow of 0% results in a duty cycle of Idle Actuator Solenoid Minimum.
An Idle Mass Flow of 100% results in a duty cycle of Idle Actuator Solenoid Maximum.

This system can control a two- or three-wire solenoid:

For a two-wire solenoid:
- Configure Idle Actuator Solenoid Normal Output Resource.
- Set Idle Actuator Solenoid Normal Output Frequency.
For a three-wire solenoid:
- Configure Idle Actuator Solenoid Normal Output Resource.
- Set Idle Actuator Solenoid Normal Output Frequency.
- Configure Idle Actuator Solenoid Inverting Output Resource.
- Set Idle Actuator Solenoid Inverting Output Frequency.

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