About Knock Control
Knock (also called "detonation") is an erratic form of combustion that can cause catastrophic engine failure. Detonation occurs when excessive heat and pressure in the combustion chamber causes the air/fuel mixture to auto ignite. This produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading. Mild or occasional detonation can occur in almost any engine and often causes no harm. But prolonged or heavy detonation can be very damaging.
Detonation causes three types of failure:
- Mechanical damage (broken ring lands, hammered big end bearings)
- Abrasion (pitting of the piston crown)
- Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)
MoTeC's Knock Modules provide individual cylinder closed loop knock control, allowing tuners to safely optimise high performance ignition maps. There is a standalone module and a version specifically designed to mount onto an M800 Plug-In ECU.
To set up a reliable electronic knock control system it is necessary to determine knock levels accurately and differentiate knock from normal engine noise. Most modern engines are fitted with a piezoelectric knock sensor. MoTeC’s Knock Modules use these sensors to measure engine noise and detect the knock levels by reducing the influence of background engine noise using a combination of data gating and frequency filtering.
A competent tuner needs to carry out a frequency analysis to determine the target frequency and knock module settings. This is highly specialised work and therefore the MoTeC Knock Modules will only be available through authorised dealers that have undertaken specific training.
When the Knock Modules settings are determined, the ECU can be configured to monitor the knock levels and to retard the ignition timing for an individual cylinder or all cylinders if the knock level exceeds a predetermined value, thus protecting the engine against excessive detonation.
SKM - Standalone Knock Module
This module is housed in a robust aluminium casing that can be mounted in the vehicle as required. It is wired between the ECU and the OEM fitted knock sensor.
OKM - Onboard Knock Module
This module is fitted onto the board of an M800 Plug-In ECU prior to delivery and linked to the knock sensor.