tony94s4

iTrader: (1)

I will be using rx8 knock sensor, in the rx8 it is hooked with two wire shielded cable adaptronic has one wire shielded, how do i wire it with the 440 universal ecu?

0110-M-P

iTrader: (10)

Correct me if I am wrong, but I believe that one wire is for the signal and the other wire is a ground.

http://www.twinturbo.net/nissan/300z...w-to-Test.html

tony94s4

iTrader: (1)

On the harness I have there are two wires going to sensor plug and not the shield

AdaptronicAus

That's right, one is shield and one is the signal.

On some knock sensors, the shield is actually connected to the sensor body. You can check this with a multimeter (just measure the continuity between the body and each of the 2 pins). If both are open circuit, then connect the shield to one of the pins, the signal to the other. It doesn't matter which way around they go.

If the body of the sensor is connected to the shield, then don't connect that pin; just connect the other pin to the signal wire in the cable, and leave the shield unterminated. If you were to connect the shield, it would case a ground loop, which is A Bad Thing (tm).

0110-M-P

iTrader: (10)

Even if the body of the sensor is connected to the shield, would it be better run a shielded wire from the knock sensor (shield on one terminal, signal on the other) to the ecu and then terminate the signal at the knock input on the ecu and the shield to a chassis ground near the ecu rather than leaving it unterminated? (Or maybe a sensor ground on the ECU?)

AdaptronicAus

No, because that will create a ground loop. The sensor ground from the ECU can't be connected separately to the body or engine ground.

I wrote a post on it a while go here: Ground loops explained

Cheers!
Andy

0110-M-P

iTrader: (10)

Thanks. I understand that a sensor ground cannot be connected to a chassis ground.....honestly, I'm not really sure what I was thinking when I wrote that question. Let me rephrase (i.e. ask the correct question)...

If you were to replace the FD's single wire knock sensor with a dual terminal knock sensor, would it be better (or worthwhile) to run a shielded wire from the 2 pin knock sensor (signal wire connected to one terminal and shield connected to the other terminal), then terminating the signal wire at the ecu input and leaving the shield unterminated near the ecu rather than just terminating the ground where the sensor mounts to the block (leaving the rest of the wire unshielded)?

Is this how it is done on most cars with a factory 2 wire knock sensor like the one used on the rx8?

Also, is there any benefit to using a more modern knock sensor over the factory FD one?

Sorry, if these questions seem kind of elementary...I don't have much experience with wiring knock sensors.

Thanks.
M-P

AdaptronicAus

Hi,

It would be better to leave the shield terminated at the ECU, because the ECU's ground is cleaner than the engine ground.

Most cars have a proper 2 wire knock sensor where the sensor is not electrically connected to the body, so you can ground it back to the ECU.

Having a 2-wire sensor where the knock sensor is electrically connected to the body basically makes it the same as a 1 wire sensor like on the FD.

I would advise leaving the factory knock sensor unless we have strong information to do the contrary; the reason being that generally the OEMs choose / design the sensor so it's sensitive to the right frequencies of that particular engine (on a piston engine, the bore size changes the knock frequency - I'm not sure what determines the sound on a rotary).

No need to apologise about the questions

Cheers!
Andy

0110-M-P

iTrader: (10)

Thanks Andy. I have no reason to change out my knock sensor (I actually have a spare, so it makes more sense to keep it)...just figured I would ask the questions in case there was some real benefit that I or someone else could take advantage of.

AdaptronicAus

No worries