Hi All,

 

I've just checked the resistances of the det sensor and its ECU connector. Det sensor is reading 0.533 Mega Ohms rather than 1Mega Ohm as expected - I suppose it may just be completely sh*gged but if not, will the lower resistance make it more or less sensitive to det noise?

 

ECU resistances are OK.

 

I'm using an AVC-R so safety boost is no longer possible but from recent posts it appears my ignition may be being retarded which is making my engine run hot due to the high AVC-R controlled boost - this is making things worse and accelerating the detting from what I can gather...surely bypassing the det sensor in my situation can't make things worse but can improve things...?

 

Any suggestions gratefully received.

 

RobH

MY DET SENSOR READS 1.35 MEG OHMS AND IS SHOWING CODE 34. HOW BIG A JOB IS IT TO JUST REPLACE SENSOR? I HAVENT GOT TO DRIVE MY CAR WITH FULL BOOST YET.

 

IM CONSIDERING BY PASSING TEMPORARILY

 

CHEERS ...LEE

Hi Lee, very big job apparently. I think it may be possible with the plenum removed but may be an engine out job - biggie which ever way you look at it :(

 

Cheers!

 

RobH

Originally posted by RobH

will the lower resistance make it more or less sensitive to det noise?

 

The det sensor is a piezo electric transducer, so I'm afraid all you can really tell from the resistance is that.. it's buggered.. I would say, from my understanding of piezo electric sensors, that your low resistance means the core of the transducer is breaking down, allowing electrical conductivity between the top and bottom. Anyway, long and short, it's buggered.. With a resistance like that, and definitely if you're getting a code 34, the ECU is ignoring the det sensor anyway. At best, it simply won't be producing valid data to the ECU (it's a microphone, rather than a sensor that senses detonation, really. The ECU just 'listens' to the sound from the detonation sensor and tries to pick out what detonation might be via the use of a set of filters.)

 

 

from what I can gather...surely bypassing the det sensor in my situation can't make things worse but can improve things...?

 

If you're already suffering det then in a way, yes, you certainly can't make it worse.. If I was in your position, then I would probably bridge the connector with a 1MOhm resistor and see what effect that had on things - but I'd be listening very carefully for that det. If it doesn't go away then you have other problems, and your det sensor malfunctioning is only part of the equation - they all need to be fixed, obviously, not just one..

 

Originally posted by LEEZX

MY DET SENSOR READS 1.35 MEG OHMS AND IS SHOWING CODE 34. HOW BIG A JOB IS IT TO JUST REPLACE SENSOR?

 

Dude, lose the caps.. ;) (It's like shouting.. and it's damned hard to read). Anyway, moving on;

 

It's a fairly large job, even by Z standards. You have two options - remove the upper and lower inlet manifolds, replace sensor and harness, then refit manifolds, which will require all new gaskets, and probably new under manifold coolant hoses.

Or drop the gearbox and do it from below - you can only really do it this way if you've done it before, however, as you need to do it all by feel, and already know where everything is.

[edit because Rob posted first]

Either way, you don't have to remove the engine, but it's not a quick job..

[/edit]

 

I think I covered it in slightly more detail in a previous post - if you do a search it should come right up ;)

 

HTH,

Aaron

Cheers Aaron, I'll be saving up for a 1MOhm resistor then...;)

There's a tech article on TT net about alternative locations for the Det sensor. A hell of a lot easier than replacing it in the stock location.

no caps is that better aaron?

 

has anyone any views on re positioning det sensor? obviously where it is as standard is best place for it but surely relocating is better than bridging with resistor.

 

cheers ...lee

Originally posted by LEEZX

no caps is that better aaron?

 

Ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh..

(Big sigh of relief from reader with tired eyes ;)) :)

 

The tech article that John refers to is here;

 

http://www.twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=786419

 

I have my doubts as to the effectiveness of any of the locations, though I think the best one may well be the first that's shown (back of the passenger cylinder head, on No6 cylinder, which usually runs hottest and is most prone to det anyway).

 

However, nobody has really tested these mods.. I mean, you could (if you'll pardon the extreme example) ducttape the sensor to the bonnet and say "Hey, it works! Code 34 gone, no det, and the ECU isn't complaining".. Sure it isn't, but it isn't able to hear any potential det either.

 

Since the ECU works by filtering the sound waves from the head, it is most likely 'looking' for a specific set of noises..

 

Now, if you alter the position of the microphone (det sensor in this case) you could very well alter the sound traces beyond all recognition as far as the ECU is concerned - it would only take a slight shift in frequency say to no longer be classed as 'det' by the ECU. And certainly, listening through something bolted to an ally head or manifold (a very 'light' metal, not that dense) is going to be different to listening through something bolted to a cast iron block (much more dense, if I'm right). I would say that the sound would appear 'higher pitched' when listening through the ally head/manifold.

 

Anyway, what I'm saying is, until someone shows me output from an oscilloscope hooked up to two det sensors on the same engine, and they're showing the same output under normal and det conditions.. I'm not convinced that these solutions are any better than the 1MOhm resistor trick.

 

I stand to be corrected, of course :)

 

Aaron

Nobody has mentioned the short cable/lead to the sensor.

This gets VERY hot and goes brittle with age and fails.

For the sake of about £20 change it.

Also the sensor i think is about £100 from courtesy - a good

exchange rate at the mo with the $

 

Mark

Kinda think I said 'replace the sensor and harness' in my original post Mark ;) :D :D But yes, you're right - it's worth emphasising too, the harness goes manky with age, probably more often than the sensor itself.

 

Then again, I found my sensor in two halves! :o Goodness only knows how that happened - looked a bit like a HT lead boot after a good arcing session..

SPL parts sell a det sensor that works with the Z32 ECU, I have bought one but have yet to see how effective it is, but I still believe it works in conjunction with the oem det sensor!

 

Has anyone got a good link to translate Japanese Instructions?

Mark/Aaron, does the cable disconnect from the sensor? (I'm not in a position to check at the mo) or is it a 'cut and solder' job. From what I saw of my cable last night it could be part of the problem. It's not really damaged but does look like it's been exposed to a lot of heat. Seems a bit of an odd arrangement - looks like it has some kind of 'noise shielding' around it too.

 

Cheers

 

RobH

Rob

 

The original harness or lead has a plug on each end, so don`t

cut anything.

There are 2 connections at the large plug end but only 1 repeat

only 1 at the sensor end - and yes i think the cable is screened.

As i said before for the sake of £20 why not replace it?

I replaced both on mine (from courtesy) and all was ok.

But its not an easy job - good luck

 

Mark

This may be a stupid question, but if it's possible to replace the harness without taking most of the car apart, why isn't it possible to replace the sensor at the same time?

 

I presume the harness plugs into the sensor, so you'd have to get to the sensor to unplug the harness? :confused:

bypass the sensor with the resistor and buy an aftermarket det sensor, adamr has just had one fitted to his

The stock det sensor is virtually useless anyway, it only detects detonation up to 3500 rpm!

Get a new AFC-II to match your AVC-R; it has a built-in 'knock sensor; ;)

Dave

Get a new AFC-II to match your AVC-R; it has a built-in 'knock sensor

 

....which works off the standard one attached to the car AFAIK so useless :p;)

 

 

The stock det sensor is virtually useless anyway, it only detects detonation up to 3500 rpm!

 

Yep, true. However, it was only designed to work with the engine in stock form ;) It certainly wasn't there to detect det caused by overboosting etc. The idea is that det will occur before 3500 on bad fuel and the ecu can perform the necessary measures to prevent damage. It's basically a protection against bad fuel... Over 3500rpm there is too much background engine noise for the stock sensor to 'hear' the det occuring.

 

CheerZ,

 

Andy