[urq] TR : RE : What causes knock ?

Louis-Alain Richard laraa at sympatico.ca
Fri May 12 16:48:24 EDT 2006

Here is an answer to my post from Frank de Kat that he forgot to send to
the list.





 -----Message d'origine-----

 De : fdekat [mailto:fdekat at sentex.net]

 Envoyé : 12 mai, 2006 12:28

 À : laraa at sympatico.ca

 Objet : Re: RE : [urq] What causes knock ?


 Hello  Louis-Alain:



 > Exactly like in my case... I replaced the air filter last week and

 > replaced some more rubber hoses that looked not perfectly sealed, and

 > pinging appeared...



 Ok. so looks like you may be onto something..


 > Mine looks OK. But in any case, I'll remove it and test it with the

 > MightyVac.


 Yes, that wold be a good idea. Really, it's the whole line, from

 to ECU that you want to be testing. I think that the line to the ECU
"Y's" to the stock bbos gauge too..??



 > I my case, the story is similar has I've seen as much as 1.9Bar on

 > dash gauge, a figure I've never seen before. And the car feels faster

 > than ever, even with 3 guys + tools aboard heading for parts hunting

 > a scrapyard yesterday.


 I don't think I ever noticed more boost, but jut pulling harder because

 the timing.


 Maybe... You have an 'overboost' situation instead, and that's causing

 pinging?  (Although, you shold get the overboost cutout then, no?)



 > Since I still have Brady's chipped ECU, this will be an easy test:

 > the ECUs.

 I'd think so!


 > In fact, I've reinstalled my stock ECU because I was thinking

 > the chipped one had some issues (long hot start, FV buzzing too hard,

 > inconsistent idle). Now, come to thing of it, it was probably fine,

 > I have problems elsewhere...

 Maybe. BUt then, there are always *plenty* of troubles to share around

 an old Audi!



 > > No surprise that my head gasket failed in there somewhere too!

 > That's my biggest fear !

 Keep you foot off the 'boost pedal' then!



 > > So, short form:

 > > Make sure the ECU IS seeing manifold signal, and that the ECU

 > > transducer is working!


 > First part is easy, with a T and a standalone boost gauge.



 > Second part, you may have to help me about this. Is this as easy as

 > applying boost to the ECU PT (while on the bench) and measuring the

 > output of the pressure transducer ?

 Basically. I'd have the ECU powered up in the car, with the cover off,

 measure the output of the tranducer. I don't remember what wire is the

 output. I can look when I get home if you like.


 Simply put, one wire is ~5V reference, one is ground, and one is

 At steady state, motor not running, the output should be mid range of

 ~0 to 5 volt range ) to 2 bar range), as it's an 'absolute' pressure

 transducer, with a pressure at rest of ~ 1 atmsophere (or 1 bar). So
one lead shold be in the 2-3 volt range.   ANd changing the pressure on
the tranducer should show some change in the output.


 > Isn't it better to look at timing

 > (with a timing lamp) while pressurizing the PT, engine running ?

 Well, you could do that too!

 But I found the above easier (As I don't have a mityvac). Besides, I

 *like* messing around with electronics!



 FYI: I've read that later pressure transducers can be made to work in

 MAC 02 ECU. Problem is mounting them, as the newer tranducers are part
of the ecu, and not a separate device. But could be done!


 Basically, you can take this transducer board:


 And mount it in/near your older ECU.  (Nothing says it has to go in the

 ECU case!)


 (From: http://www.sjmautotechnik.com/trouble_shooting/pinout.html#otwo




 In my case, that seemed kind of silly to me, wrecking up a good MAC11,

 make a MAC 02 work!  I just switched everything over to the MAC 11

 Now I have knock sensing, and ECU frequency valve control of the

 and the ability to pull codes and do tests.


 I hope this gives you even more to think about!


= Frank=

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