The Bosch Motorsport KS4-R knock sensor detects structural vibrations in the engine block associated with detonation (knock) — uncontrolled autoignition of the air/fuel mixture ahead of the flame front. A piezoceramic sensing element with a seismic mass responds to block acceleration: as the engine vibrates during a knock event, the seismic mass moves relative to the sensor body, compressing the piezoceramic element and generating a voltage signal proportional to the vibration magnitude.
The ECU monitors this signal in the knock frequency window (engine-specific, typically 6–12 kHz for most four-stroke gasoline engines) and retards ignition timing on the affected cylinder whenever signal energy crosses the threshold. The KS4-R’s 3–25 kHz broadband response covers the knock frequency range of virtually all gasoline engines from single-cylinder karts to V12 GT cars.
The KS4-R uses a broadband design — it does not contain a resonant tuned element, so the ECU applies a bandpass filter in software for the specific engine’s knock frequency. This makes it universally applicable across different engine types without needing to select a frequency-matched sensor. It mounts directly to the engine block, typically one per cylinder bank.
Technical Specifications
| Property | Value |
|---|---|
| SKU / Part number | 0261231173 (0 261 231 173) |
| Sensor type | Piezoceramic broadband knock (detonation) |
| Frequency range | 3 – 25 kHz |
| Sensing principle | Seismic mass + piezoceramic element |
| Output | Voltage proportional to block acceleration |
| Sensor head height | 18 mm |
| Weight | 82 g |
Applications
| Application | Notes |
|---|---|
| Engine knock detection | Block-mounted per cylinder bank |
| Ignition timing optimisation | ECU uses signal for closed-loop knock retard |
| Detonation monitoring (data logging) | Log knock sensor voltage for calibration sessions |
| Compatible engines | All gasoline engines — broadband design covers 3–25 kHz |
Related Products
- MS 6.4 EVO ECU — ECU with 4 knock inputs (MS 7 family)
- MS 7.4 ECU — 4 dedicated knock inputs
- Bosch Motorsport C70 Data Logger — for knock signal logging
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