Knock Tuning
Setting knock acceptable level thresholds by RPM and load
The Knock page displays logged knock sensor level data and lets you set the knock acceptable level thresholds in your ECU map. The threshold defines the level above which the ECU considers knock to be occurring. Setting it too low causes false knock events and unnecessary timing retard; setting it too high allows real knock to go undetected.
2D vs 3D knock tables
Some ECUs (notably Haltech) use a 3D knock table with both RPM and Load (TPS) axes. Others use a simpler 2D table with RPM only.
- 3D knock (Haltech) — A TPS column dropdown appears. Select a TPS breakpoint to view the knock threshold slice for that throttle position.
- 2D knock (ME, MegaSquirt) — No column selector. A cylinder dropdown lets you view data for a specific cylinder (1–4) or all cylinders combined.
How to set thresholds
- Collect a log that includes data at normal operating conditions — not during any detonation events.
- On the Knock page, observe the scatter of knock sensor readings across the RPM range. Green points represent good steady-state data.
- The threshold should sit above the noise floor of the knock sensor (the scatter at normal operation) but below the level expected during actual knock.
- Adjust the threshold values in the table. A common starting approach is to set each cell to approximately 1.3–1.5× the peak noise level observed at that RPM.
- Click Update to commit, then save and reload the map to the ECU to verify.
Important
Knock threshold tuning should always be done conservatively. If in doubt, keep the threshold
lower rather than higher. Actual detonation can cause serious engine damage very quickly.
Test on a rolling road or in controlled conditions where knock can be monitored independently.
Editing the table
Knock threshold values are integers (no decimal places). Select cells and use the same increment/decrement and set-value shortcuts as on other tuning pages. See Keyboard Shortcuts.