[urq] MAC 02 Pressure Transducer failure?

[Pasqualoni, James E]

Fyi-I got massive pinging when I developed a leak in the pressure hose from
the IM to the pressure transducer.  Test this line, and the tee to the boost
gauge for leaks if you haven't already.

HTH,
Jim 

-----Original Message-----
From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On Behalf
Of Buchholz, Steven
Sent: Friday, July 08, 2005 6:02 PM
To: urq at audifans.com
Subject: RE: [urq] MAC 02 Pressure Transducer failure?

... doggone ... missed on point ... sorry for the follow on ...

One of the other things to beware of is that the reference pin location is
different for a WX and an MC engine ... it is not a simple matter to wire a
MAC-02 onto a WX engine unless you accommodate this change ...

Steve B
San Jose, CA (USA)
> 
> ... actually the computer does not "adjust everything" ... all it
really
> adjusts is the ignition timing ... and pinging is something that can 
> occur even without a spark.  You may have a screwed up mixture in one
or
> more cylinders caused by malfunctioning injectors.  Before getting too 
> far into things you might want to investigate this by reading the
spark
> plugs.
> 
> You may want to consult the IST docs to help with your understanding
...
> 
> 
> 	http://www.quattro.ca/Urq/urq-IST-Introduction.pdf
> 
> On page 18 it shows how the F/TCU changes the timing based on boost
...
> if you had a PT that was indicating there was no boost, when in fact
the
> engine is seeing full boost the diagram shows that the timing would 
> likely be *retarded* from optimum (for example the ignition timing at 
> 4000RPM at 0 bar is almost 40 degBTDC, where at max boost it is 
> something like 15 degBTDC).  I just read the doc ... it indicates that
a
> faulty Intake Air Temp sensor might be responsible for pinging.
> 
> Nevertheless, the faulty pressure transducer is something you should 
> fix.  It could well be contributing to the problem ... at the very
least
> it means your engine is not operating optimally.  Unfortunately you 
> can't just hack in a constant value for the manifold pressure ... the 
> F/TCU looks for the boost to be too high at low RPMs and will shut off 
> the fuel pump.  It is pretty clear that the PT module that was used
with
> the MAC-02 is NLA, but there's no reason a functional equivalent could 
> not be manufactured ... this would provide a good opportunity to put
in
> a higher rating device e.g. 2.5 or 3.0 bar, which could be combined
with
> a remapping based on the info RDH compiled on the MAC-02 to allow
higher
> max boost.
> 
> There is some justification for going ahead with the MC/MAC-11 swap
...
> there the big gain is the knock sensor and WGFV boost control
mechanism.
> The downside is those stupid hydraulic tappets that Audi uses.
> 
> Hope this helps you with your troubleshooting and decision making!
> 
> Steve B
> San Jose, CA (USA)
> >
> > SO the next thing is, how do you get pinging, if the computer
adjusts
> > everything?
> >
> > Martin P tells me about the known 'pressure transducer failure'.
> >
> > So today I wired up some leads to the transducer, so I could measure
> it's
> > output while driving.
> >
> > Surprisingly enough, there was no output. I assume that means the
ECU
> thinks
> > it's seeing full vaccum all the time.
> >
> >  That cold explain the pinging..!
> >
> > So my questions are:
> > 1) What's the chance that replacement transducers are available?
> > (Probably unobtanium, so I may as well go to a MAC 11 ECU and
harness,
> as I
> > already have the block, head and turbo..?)
> >
> > 2) I'm sure I've seen a spreadsheet somewhere, that shows transducer
> output
> > vs transducer pressure. Anyone else know where to find that?
> >
> > I could then substitute the pressure transducer output with a fixed
> voltage,
> > closer to what the ECU would want to see for near full boost. At
least
> then,
> > It won't ping so much (But have other side effects of never changing
> value
> > either).
> >
> > 3) Or any other ideas?
> >
> > It's the MAC 02 with the 'yellow' label, if that makes any
difference?

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