What is a Knock Sensor

[Massimo]

Ok so i understand if i want to turbo or supercharge my m42 i need a knock sensor. What the hell is it, how dose it work? Iv tried looking but can't find anything. PLEASE EXPLAIN

Thanks Massimo

[ZiMMie]

http://www.youtube.com/watch?v=0xI94ZDF54Y

[Massimo]

Thank You but my work has blocked youtube. Yes it sucks.

[SpecM]

it detects engine knock
and sends a signal to the ECU to do something about it

[winfred]

it's a coil of wire around a core that picks up a certain vibration and turns it into a voltage signal the computer can read, the output of the coil is tuned to the frequency of preignition knock so normal noise doesn't set it off, you can usually harvest sensors from other cars, you can test them with a multimeter by bolting the sensor to something and popping the bolt with a hammer lightly watching the AC voltage pulse on the meter, much easier with a graphing meter though

[Jean]

A "microphone"

[SpecM]

it's a coil of wire around a core that picks up a certain vibration and turns it into a voltage signal the computer can read, the output of the coil is tuned to the frequency of preignition knock so normal noise doesn't set it off, you can usually harvest sensors from other cars, you can test them with a multimeter by bolting the sensor to something and popping the bolt with a hammer lightly watching the AC voltage pulse on the meter, much easier with a graphing meter though

the problem is that preignition "sounds" different in every motor, so the knock sensers will be "tuned" differntly

didn't the m44 have knock sensers?

[Justin B]

For megasquirt I know there's someone out there that makes little knock sensor add on boxes, and will either supply or you can buy standard bosch knock sensors. One thing they want to know though is the diameter of the cylinder wall so it will tune into the frequency of the sound wave inside the cylinder. Something like that. When/if I put knock sensors on my m20 i'll try to find something with a similar bore size, like e36 since its +2mm.

[SpecM]

For megasquirt I know there's someone out there that makes little knock sensor add on boxes, and will either supply or you can buy standard bosch knock sensors. One thing they want to know though is the diameter of the cylinder wall so it will tune into the frequency of the sound wave inside the cylinder. Something like that. When/if I put knock sensors on my m20 i'll try to find something with a similar bore size, like e36 since its +2mm.

m50s have the same bore as an m20

[winfred]

yep, so did the later m42

didn't the m44 have knock sensers?