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G4x monsoon + plex knock monitor v2?

Link G4 Plus Software Tutorial

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I have a newbie question here: my g4x monsoon doesnt have a knock input, but is there a way to set up some sort of knock control strategy by using an external knock monitoring system like the Plex v2, via one of the analog inputs, or CAN?

the plex manual says its 0-5v analog output has several modes:

Options available:

1) Knock signal from sensor 1(current signal from knock sensor after passing set filter linearised to the 5V range. 0V = level 0, 5V = level 255)

2) Knock signal from sensor 2(current signal from knock sensor after passing set filter linearised to the 5V range. 0V = level 0, 5V = level 255)

3) Max of the signals from both sensors(the higher of the 2 signals above)

4) Knock threshold level(the current calculated or set knock threshold level. 0V = level 0, 5V = level 255)

5) Total knock count(0V = 0 count, 5V = 255 count, count can be reset on device or via the software if it reaches maximum)

6) Knocking cylinder number indication(voltage level indicating which was the last cylinder that knocked.

0.625V cylinder 1, 1.25V cylinder 2, 1,875V cyl3, 2.5V cyl4, 3.125V cyl5, 3.75V cyl6, 4.375V cyl7, 5V cyl8

7) Ignition retard(output goes above 0V if knock is detected and slowly ramps down if no knock is detected, can be used to add basic knock control to an ecu)

8) Knock warning( output goes to 5V when knock is detected and to 0V when there is no knock.

9) Fixed 0V, used for calibration and test purposes

10) Fixed 5V, used for calibration and test purposes

is there any mode on the list that monsoon ECU could use to achieve some degree of knock control (global ignition retard based on option 7 or 8, for example)? if not I'm still going to get a plex v2 for tuning and logging.


First, in PC Link, go to >help>ecu information, and take a look at the main board revision. MonsoonX with board revision V3.0 and later have knock control hardware built in.

If yours is the earlier version without knock hardware, then yes option 7 would probably be the best bet. Set it up as a GP input and span the axis of a 4D ignition table to add some retard based on knock severity.

Thank you Adam! I have a monsoon V2.4 though, wish I knew that before the purchase haha

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