Electronic Solutions for Motorsport

Knock Sensor Signal – Threshold Setup with KSC2

3 min read
Movichip news. KSC2 BT connection issue.

This article details how to setup the knock sensor signal threshold in the MoviChip Knock Sensor Controller (KSC2)

WARNING: Engine Knock can cause catastrophic damage to an engine, only follow these steps if you are sure you know what you are doing.

What is a “Knock Threshold”

Threshold is the intensity of the signal, from the knock sensor, in our selected frequency, that will be classed as engine knock.

This video covers the areas detailed in this article

Before we can set the knock sensor signal threshold we need to have identified the knock signal frequency. Check this article for more details > Knock Frequency ID tool.

With the Knock Frequency Window Programmed

We can move into the Baseline Calibration section in the KSC app.

First step is to set our “Saved” volume/threshold to a high number so we don’t interfere with the ignition timing of the engine (assuming we have the 5volt out from the KSC connected to the engine ECU)

Retarding Ignition

Next we need to make absolutely sure that the engine will not knock under full throttle. Easiest way to do this is to retard the ignition timing of the engine, if you can’t do this, using the highest octane fuel possible will help.

Mid RPM & Redline

Next we choose our RPM range midpoint and our RPM redline. Usually I like to chose a mid point of around 3500 rpm for an engine with a 7000 rpm redline, and set the redline around 500-1000 rpm below the actual rev limit of the engine.

Full Throttle Run

Now we have the engine in a state where we know it will not knock and with our RPM points set, we can switch the Baseline Calibration option to “On” and carry out a full throttle run in one gear.

NOTE: In the video the car is driven at different RPMs and throttle positions for a period of time. It is now recommended to carry out one full throttle run and press the “Off” button just before we lift of the throttle at redline.

Lifting off the throttle usually creates a frequency similar to knock in the engine, we want to ignore this, the engine is under vacuum when the throttle is lifted so this sound is irrelevant.

Peak Volumes

When we press “Off”, after a few seconds the peak volumes experienced during the run will be outputted onto the screen of the KSC app next to “Peak Volume”.

This process can be repeated to get an idea of the peak volumes that are normal. When we are comfortable we have identified the normal “Peak Volume” we can transfer these volumes to the “Saved Volume” line. A number or two can be added to the “Peak Volume” norm to limit false positives.

Our knock sensor signal threshold has now been set and saved.

Validation – Knock Sensor Signal Threshold

To validate the knock signal threshold entered, the ignition timing can be advanced further than what is normal, driving the vehicle with this exaggerated ignition timing at light engine loads should lead to very light engine knocking and the KSC outputting the 12v and 5v signals to indicated engine knock.

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