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Old 10-19-2000, 08:21 PM   #1
8Complex

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Post Anyone try this with the stock knock sensor?

Anyone try wiring in a relay so that it lights up an LED or a small bulb when it reacts? I imagine it'd be like the poor man's J&S, somewhat, but it might help...
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Old 10-19-2000, 08:26 PM   #2
Penphoe
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00 Impreza RS GM6 RIP

Question

Where does the stock knock sensor live on the engine?

LaterZ!
Darren!!
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Old 10-20-2000, 03:22 AM   #3
Jay_UK
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Post

You wont be able too.

The sensor is a high impedance device...
You will throw a check light if u connect a low impedance device onto it...

Either get a new knock sensor (cheap).. or fit a isolating/buffer circuit between the sensor and your output device.

Or just be a cheap knock sensor unit (knocklink) that is adjuatble

J.

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Old 10-20-2000, 05:49 AM   #4
Scooter
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Post

The knock sensor is always picking up noise, so the LED would be flickering or on most of the time. Knock has a characteristic sound and occurs during a specific window of time relative to TDC. Unless you have all of the same knock detection circuitry as the the stock ECU wired up to the LED, then the LED will light up for more than just knock. If you want to monitor the knock signal to determine what's knock and what's not for yourself, then you would probably need a scope and you would have to know what to look for.

You would probably be better off getting an OBD II scan tool and watching to see if the ignition timing is being retarded. Or finding some other method of tapping into the ECU after the processed knock signal has been compared to the knock threshold.

Buying something else like the J&S Safeguard or Knocklink (as Jay suggested) can be quite useful, but since the have their own knock dectection circuitry (and are adjustable) they may not indicate knock at the same point as the stock ECU. Thus, such a device may not indicate knock, yet the ECU's knock theshold has been exceeded and timing is being dailed back. Unless you know the stock knock threshold and and the type of detection circuitry being used, it would be pretty tough (if at all possible) to get such a device to detect knock at the same point as the stock ECU.

In a way, the term "knock sensor" is misleading. It doesn't sense knock and knock alone. It's a piezoelectric microphone that picks up all kinds of engine noise. Maybe they should call it the "Engine block noise sensor". It just so happens that the signal from this noise sensor is used by the ECU for the sole purpose of knock detection.


[This message has been edited by Scooter (edited October 20, 2000).]
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