Is Audio Knock Detection Setup ESSENTIAL?
September 24, 2025The instructions for the KSC3 engine knock detection system, make reference to listening to engine knock audibly as part of the setup process for the product. But is it essential to be able to listen to knock audibly?
Knock Detection Setup
A critical part of setting up a knock detection system is being able to discern between what is normal engine volume in our frequency detection window and what is not normal.
Specifically knowing what the engine sounds like when everything is working normally versus when the engine is knocking/detonating.
Ultimately, without being able to listen to the engine, we can’t be sure it isn’t knocking when we are setting our baseline volume thresholds.
Educated Guess
If we have no way of listening to the engine (which is unlikely given how easy it is to DIY, but say we can’t) or don’t want to, there are some obvious things we can do to minimise the chances of the engine knocking when we do our baseline runs.
Fuel
Put in the highest octane fuel we can when we do our baseline volume threshold runs.
Water Injection
If we have water injection on the engine, use it during the baseline runs.
Conservative Timing
If we can retard the ignition during the base line runs we should probably do it.
Not Heat Soaked
Doing a baseline run on an engine that is not heat soaked will be beneficial. Have the coolant temps as low as they go at normal operating temp.
Rich AFR
Running the engine with a safe rich mixture.
Disconnect MAF/Lambda Sensor
This may or may not work depending on the car. Some engine ECUs will default to rich mixture if the lambda sensor is not connected. AFRs must be monitored to ensure this is the case. Disconnecting the MAF/Lambda may also put the engine into limp mode. Definitely a trial and error method this one. We need to be sure what the engine ECU is doing with the MAF/Lambda sensor disconnected before we think about doing full throttle pulls.
Engine ECU Timing
Monitoring the engine ECU is a good way to see if the engine is pulling timing due to the signals it is getting from the existing knock sensing setup. We may be able to monitor timing pull directly or we may have to log overall ignition timing over a run to see if we are getting any unusual dips in the timing numbers against load & RPM.
Conclusion
There are steps that we can take to minimise the chance of our engine knocking during the baseline calibration of our knock thresholds. If we can do them all, that’s great, but we will still be hoping that our engine didn’t knock. We have minimised the risk but the risk is still there. And given how we will monitoring knock in the future, is it worth the chance of using an uncertain knock threshold to tune an engine? That is up to the person doing the tuning.
Is audio knock detection essential when we setup our electronic knock detection system? If we want to be 100% sure I think yes, if we think we can get as close as makes no difference to being sure the engine is not knocking then maybe not. It depends on the engine, how much load we are putting through it, what measures we can take to minimise knock and so on.
But given how easy it is to setup a rudimentary audio knock detection setup I think I would still lean towards doing that. At the end of the day I think it’s easier because we may have an engine that isn’t knocking in it’s current state of tune so we don’t need to do any of the things mentioned above.
