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Wiring Fundamentals: Knock

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Knock

01.14

00:00 - Knock or detonation is the number one killer of performance engines, and for this reason reliable knock detection is an important consideration when designing a wiring harness.
00:10 Automotive knock sensors are peso electric microphones bolted to the side of the engine block, usually near the interface to the cylinder head.
00:18 These peso electric microphones convert the vibration of the engine block into an electrical signal.
00:23 The amplitude of which varies with the strength of the vibration.
00:26 However the signal they generate is still very small and for this reason it must be run to the ECU using shielded cable.
00:33 The ECU uses dedicated internal circuitry to monitor the knock sensor signal and will have specific pins the knock sensor needs to be wired to.
00:42 Aftermarket motorsport knock sensors typically have two pins.
00:44 One of which is wired to sensor ground, the other to the knock signal input, and the polarity of them is not important.
00:51 If your engine has a knock sensor fitted from factory that you would like to use, you'll need to contact your ECU manufacturer's technical support department to determine if it's possible to interface to it and what the wiring configuration should be.
01:04 In most instances it's not a problem to use the factory knock sensor.