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Single vs twin wire knock-sensor


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4 replies to this topic

#1 RedRX

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Posted 19 November 2003 - 03:32 AM

The engine in my RX is supposed to have a twin wire knock sensor. It has the separate knock control unit in the fender (ah - 80s technology:-\ ). It aparantly works by producing and alternating current. Thing is - someone has fitted a later SINGLE wire sensor and simply bodged it by soldering the single wire to BOTH wires coming from the knock control unit. How does the single wire sensor signal knock compared to the twin wire setup? I have removed the green wire from the knock control unit and simply run this to ground and left the red wire conected to the sensor - but i imagine this has achieved little.

Funnily enough - i have never had the car ping - let alone knock!
Any ideas anyone?

#2 RedRX

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Posted 20 November 2003 - 03:57 AM

Riiiight - i take it no-one has a clue?

#3 Skip

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Posted 20 November 2003 - 05:09 AM

Red, the signal from the knock sensor is AC but a very complexe wave form, the KCU (Knock Control Unit) has filters for letting the proper signal pass into the sensing circuit.
You are correct the two wires (red and green) and a shield are for the proper sensor. The green wire is called negative by the FSM so it may be an earth ground? You could check with a DMM for continuity to ground on the green wire. If it shows resistance, I would get the proper KCS.
I assume you have the rare bird 85 or the 86 model with a Flapper door MAF.
Hope this helps some, but again you are correct as I ain't gotta clue, my expierence is with hot wire MAF'd cars, still on a steep learning curve with flapper doors.

#4 RedRX

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Posted 20 November 2003 - 06:13 PM

Thanx Skip. I love the way you give all the useful info I needed then say you dont have a clue! Modesty. Hehe - now I just gotta get my hands on a twin-wire sensor. I imagine the KCU would just get gobbleygook from the current sensor.

#5 stngllhm

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Posted 28 September 2004 - 11:02 AM

The engine in my RX is supposed to have a twin wire knock sensor. It has the separate knock control unit in the fender (ah - 80s technology:-\ ). It aparantly works by producing and alternating current. Thing is - someone has fitted a later SINGLE wire sensor and simply bodged it by soldering the single wire to BOTH wires coming from the knock control unit. How does the single wire sensor signal knock compared to the twin wire setup? I have removed the green wire from the knock control unit and simply run this to ground and left the red wire conected to the sensor - but i imagine this has achieved little.

Funnily enough - i have never had the car ping - let alone knock!
Any ideas anyone?


i'll trade you a dual wire for a single wire




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