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Knock Sensing for Subaru

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I have an EJ257 engine running with a MoTeC M130 which I plan to install and configure permanent knock control before I start to increase the boost above its current conservative settings and/or develop ignition maps for power or lower grade fuel.

I have two knock inputs available and am still fairly open whether to use 1 or 2 sensors so any input those experiences with Subaru engines would be gratefully received. I have a reliable source that informs me the OE early spec single wire Subaru work well and have been used for factory supported motorsport programmes, however, if there are other options with technology developments over the past 20+ years I would be interested in other recommendations.

The part number and image on millspecwireing.com leads me to believe MoTeC supplied sensor is a Bosch 0 261 231 045. Does anyone know if this sensor holds any advantage over the Unisia JECS sensor I already have as OE fitted?

I have access to a professional audible knock monitoring system which I will be using together with frequency analysis to set the thresholds.

The older EJ engines used a resonant knock sensor, which is basically a narrow band sensor that only picks up certain frequencies depending on the application it was designed for.

The Bosch number that MoTeC have listed is a wide band that picks up a wide range of frequencies, these can be filtered down in the ECU to the exact frequency that your engine knocks at, either primary or secondary resonance. These are used on most modern cars that I've seen and are readily available from motor factors.

I'm using the M150 with an FA20 engine that is factory equipped with two sensors. The single sensor on the EJ works just fine in my experience. You can add a second sensor but you will need to find an appropriate location to mount this - Ideally one sensor on each half of the engine block.

The stock sensors are often a tuned sensor that are designed to be most sensitive at the second harmonic of the knock frequency - If the knock frequency is for example 6.5 kHz then the second harmonic is double this or 13 kHz. This improves the signal to noise ratio. If the engine is relatively standard then the narrow band factory sensor will likely work well (this is what I'm using on the FA20 still). If for any reason your modifications significantly change the knock frequency (unlikely to be honest since the knock frequency is influenced most heavily by bore diameter) then a wideband sensor may offer better results.

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