The Transient Ignition Retard function is designed to introduce ignition retard during transient conditions. Transient conditions are identified by a fast change in Throttle Position (TP(Main)) or Manifold Absolute Pressure (MAP). Ignition is retarded depending on the rate of change of TP(Main) or MAP, then held retarded for a particular number of engine cycles.
Transient ignition retard can be used to eliminate 'snap detonation' by retarding the ignition angle when engine load suddenly changes.
The Transient Ign Trim and TP Delta Max parameters can be used to setup and diagnose the Transient Ignition Retard function:
Transient Ign Retard Settings:
The following options are available:
·OFF - The Transient Ignition Retard function is not used.
·ON - The Transient Ignition Retard function is enabled. The Transient Ignition Table will be used.
·Disabled - The Transient Ignition Trim Table remains allocated but no Transient ignition trim is calculated or applied
This is the number of degrees of ignition timing that will be restored per engine cycle after the Hold Time.
This is the number of engine cycles the ignition will be held retarded for before normal ignition timing is progressively restored.
The numbers entered in the table are degrees of ignition retard (ie they are negative).
The table should have one of its axis set to either TPS Delta or MAP Delta. To adjust the rows or columns press the X key or right click on the fuel table and select Axis Setup .
Transient Ign Retard Example
Given the following settings:
1.A value of -12 in the Transient Ign Retard Table at a particular rate of change of throttle movement and engine speed.
2.Hold Time = 5
3.Decay Rate = 1
When the throttle is opened suddenly the ignition timing will be retarded immediately by 12 degrees from its normal value. Timing will be held 12 degrees retarded for 5 engine cycles. After this timing will be advanced back towards its normal value at 1 degrees per engine cycle. It will take a total of 17 engine cycles to restore normal timing.