What the knock threshold does
A knock sensor hears everything: valvetrain, pistons, the timing chain and real detonation. The ECU turns that into a Knock Level reading. The Knock Threshold table is the line in the sand. When Knock Level rises above the threshold for the current RPM and load, the knock system treats it as a knock event. Below it, it's just engine noise.
The table can be mapped in up to 3D, so the threshold can change with RPM and load, which matters because background noise climbs a lot as revs rise.
How we set it up
- Get the tune to a point where you're confident the engine isn't knocking anywhere. Conservative timing is your friend here.
- Log Knock Level across the whole RPM and load range.
- Set each threshold value a little above the logged Knock Level for that area, about 3 to 5 dB higher.
- Confirm that genuine knock produces a clear spike well above the table. It should stand out sharply from the background.
Too low, and normal noise gets counted as knock, pulling timing for no reason. Too high, and real knock slips through. Neither is safe to leave in a tune.
Good data starts with a good sensor; a flat-response unit like the Haltech HT-011100 is what we fit. See knock control for how the ECU responds, and knock wiring for setup.
