Subaru Ignition Timing Parameters (CAN Vehicles)

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In this article, we will go through the common ignition parameters available when making logs for Subaru cars with ProECU. The ignition correction techniques for different models of Subaru vehicle vary and you will see certain parameters in some ROMs and not in other, we also add custom parameters in some of the platforms to allow for easier tuning.

The Basics

This explanation is based around the Subaru CAN Suite but it is very similar for Subaru Kline, DIT and BRZ. The most important parameters to go through are

• Ign, Cor. AK (Knock Ret.) (º)

• Ign. Cor. AP(Learnt Cor.) (º)

• Ign. Cor. AT (Coarse Cor.) (º)

Though there are other parameters which we will discuss as well.

• Knock Correction (º)

• Knock Sensor Input ()

• Knock Signal 1

• Ignition Timing (º)

• Learned Ignition Timing (º)

The logging parameters are displayed as per below in the ProECU Live Data tab, you can see which parameters are created by EcuTek or available as an OEM parameter. It is often the case that the OEM parameter is still available but the EcuTek parameter has much higher resolution or sampling rate

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The Parameters

Essentially, there are three modes of knock correction in the majority of Subaru’s. Which mode is active at which time and how the ECU learns involves some fairly complex strategies which have evolved over the different models over the years. From our understanding of Subaru’s design these modes are called, Instantaneous knock correction (AK), Advance multiplier based correction (AT) and Fine learned correction (AP).

Below is a brief description of the parameters and the intent of mode and how it works. This should be relevant for most Subaru cars, however it is drawn from the 08 WRX so other models may be named slightly differently.

Ign, Cor. AK (Knock Ret.) (º)

A custom parameter for knock correction quantity, instantaneous knock retard to suddenly retard the ignition quickly, and then advance back more slowly, but this is temporary and is not learned. This is useful for correcting for extra ordinary knock caused by extremes.

Ign. Cor. AP (Learnt Cor.) (º)

A custom logging parameter for learning correction quantity AP, Knock retard that is learnt at particular load and RPM ranges are stored in a table, when using this knock protection mode it uses the values as an addition to the final ignition value.  When ever a ‘knock’ event has been heard, the fine ignition map will subtract this value from the site in the ‘Fine Ignition Learning’ map. This prevents the knock event repeating itself again and again.

If this location specific knock event does not return, eventually the value that was subtracted from the ‘Fine Ignition Learning’ map will be added back in. It retards quickly, but the learning function to advance the ignition again is slow. This is useful for correcting small differences in the ignition maps, perhaps caused by seasonal weather differences or to compensate for some sustained heavy use like a track day.

Ign. Cor. AT (Coarse Cor.) (º)

A custom logging parameter for Learning correction quantity AT (advance multiplier x advance map) + AP learnt correction value. The initial value is pulled from fine learning tables and applied to formula to effect the final ignition amount.

This uses the advance multiplier to give an overall reduction in advance by adding only a limited proportion of the "advance map" to the "base map". It can make broad changes and is good for correcting for low octane fuel that will result in retarded ignition over most of the map, it does not change quickly. It also compensates for changes in sensors and the engine (wear, carbon build up etc) over a longer period of time. It's quite quick to lower the advance multiplier, but slow to increase it.

The other parameters are described below.

Knock Correction (º)

An OEM parameter that shows the knock correction value it uses the Ign. Cor. AP(Learnt Cor.) value but will show the positive learnt values as well if they have been learnt. Positive values are learnt up to the max values of the ignition advance map, you should see these values being added/taken from the final ignition value.

Knock Sensor Input

An EcuTek custom Parameter that shows the output of the knock sensor as close as the logging speed will allow.

Knock Signal 1

An OEM parameter for Actual signal from knock sensor it believed to be an on or off signal, with the speed of logging over OBD this parameter will only show the larger knock events.

Ignition Timing (º)

The actual ignition timing used after all corrections have been made.

Learned Ignition Timing (º)

This is the OEM version of the AP correction values we recommend using the EcuTek parameter as it includes a higher resolution and utilises a higher logging speed.