[urq] TR : RE : What causes knock ?
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
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 ?
> 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
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
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
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!
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