Knock Detection

Allows the ECU to monitor engine knock by enabling up to 2 knock sensors. Knock Detection is the configuration and setup of the detecting portion of the knock system in the ECU. For settings related to Knock Control (such as retard values and long term learning, see 'Knock Control').

The Knock Detection function can be used to test whether the knock sensors in a vehicle are functioning correctly, by temporarily advancing the timing for a set time limit, as chosen in the Knock Detection node, and then retarding the ignition timing back to the original value. 

A spectrogram function is provided to visually confirm the knock sensor readings against audible detection strategies such as 'knock ears'. It can also be used to better find the knock center frequency for the particular application. 

Detection

Knock Frequency

Select the frequency at which engine knock is occurring. This should be the frequency where there is the largest difference in signal between no knock and real engine knock. Often referred to as signal to noise ratio. The spectrum analyser below can be used for the identification of this frequency. Look for obvious signal differences when the engine is known to be knocking compared with when it is not. Alternately, right clicking on the spectrogram will give the option to Set As Centre Frequency and obtain this value.

Start Angle (BTDC)

The crank angle position where knock detection will begin to look for knock. Selecting too of an advanced angle may cause combustion noise to be seen by the knock detection system, and too an excessively retarded value can cause knock to not be detected at all. Experimentation is the best method for finding this value.

Duration

The crank angle duration the knock detection system will look for knock. Selecting a narrow duration can improve noise rejection which will give a cleaner signal, but there is also the chance that peak knock signal may occur outside of this crank angle window. Experimentation is the best method for finding this value.

Remove Background Noise

Enabling this setting will subtract the engines 'noise profile' sampled outside the knock window from the knock sensor signal within the knock window. This aids in rejecting false engine noise from the knock signals, resulting in a flatter Knock Threshold table.

In order to confirm that the knock sensors are working, the Momentary Knock function will temporarily advance timing. This is an added safety feature, as the timing will return to the desired timing after a short period of time.

Ign Adv

The angle which ignition timing will be advanced

Duration

​The period of time that the timing remains at the advanced rate before returning back to normal.

Click the 'Knock' button to activate the Momentary Knock function.

This node can be used to set and configure the various options for the Knock Detection inputs, and Knock Light output.

Knock Sensor 1 - Enable when you are using the Knock Sensor 1 Input.

Knock Sensor 2 - Enable when you are using the Knock Sensor 2 Input. Typically a second sensor is used when a V-engine, or an engine with two bank is being used.

Light Output - Enable when a light is to be used to show when knock has been detected.

Light Output Mode - Determines how the light will operate.

      Use CEL - An already configured Check Engine Light (CEL) will flash when knock is detected. When no knock is present it will perform as a normal CEL.

      Digital – Switched - When selected, a separate light output is enabled and must be wired. It will flash when knock has been detected.