Type 44 MC questions

[isham-research.freeserve.co.uk at pop.pol.net.uk]

>> a) Does anyone have an MC injection system on the bench?
>> I'd like to know the 'at rest' resistances of the plate position
>> sensor.

> I think your talking about the fuel-consumption sensor on the air-flow
> meter right? Well in that case, there's no spec in the Bentley for
> resistance, but yer actually s'posed to measure voltage. Pin1 is 5V and
> pin3 is gnd. Pin2 is the output voltage. All the sensor is a simple
> potentiometer setup as a voltage divider. To test you can apply 5V on pin1
> and 3 and monitor pin2. At rest it should be 0V. At idle it should be
> 0.2-0.5V. There's a special gadget [VW1348/1] that fits over the air-flow
> plate and holds it w/ a magnet to several set positions like idle and WOT
> [4.0-4.5V]. I've never seen one of those tools and it's prolly very
> expensive unless you know someone. I'm sure a good estimate will work just
> as well, though as the spec range is wide.

I have a VAG 1348/1 - I'll post a [URL of a] snap of it when I get back
to the workshop.  I used it some while ago when investigating fueling
issues on the MB engine - I can't remember whether the discussion was
public to the list or restricted to a few of its members - it was pretty
specialised.

It's a nicely made tool, BTW.  Not easy to use - setting it up is
difficult because the magnet pulls the plate onto itself in an
unpredictable way.  At least - it's not precisely predictable.  I
find you have to use a standard depth gauge to hold the plate at rest
while you fit the 1348/1.  You can also just fit it and zero it to
the plate rest position, but the measurement is difficult because the
1348/1 shields the bit you want to measure.

Interestingly, a standard depth gauge with a reference bar big enough
to span the cone costs more than the 1348/1.

We were investigating a fueling problem on an MB engine that
had been messed with.  I wondered how precise the output from the
potentiometer was, and so I measured a number of cars including my
own and shared the results.  We were quite astounded to find that
Bosch/Audi calibrate or adjust this thing to within 1% - by far the
closest electrical tolerance I have _EVER_ found on a car.  We were
able to derive graphs for four or five cars using the 1348/1, and
we were then able to run real road tests while looking at the position
of the plate.  It got pretty heavy at one point - Scott Mockry took
some oscillographs of a plate bounce phenomenon I predicted would be
caused by the fuel pump overboost cutout.

But if the 'at rest' position is zero (volts or ohms) then recalibration
is easy - I have my datum, so thanks.

One of the results of our experiments caused great debate - on an
ur-quattro MB engine (very close relative of the MC-1) the plate is
at full deflection by 4500 rpm at full boost.  So what supplies the
extra fuel beyond this point to redline?

Answers please on a postcard to ...

>>b) Anyone have the engine/gearbox alignment
>>specifications? I'm sure mine is touching the chassis
>>somjewhere.

> The Bentley says you only need to measure one distance. For manual
> tranny's, it's from the rearmost subframe bushings to a casting in the
> middle of the tranny w/ a dime-sized hole in it. The distance is 29.4mm.
> For A/T, it's from the rearmost subframe bushings to the first cast fin on
> the tranny under the driveshafts. The distance is 127.4mm. Hope this helps.

Right.  Next time I'm under the car ...

(Must get some Type 44 documentation if I'm keeping this beast.)

--
 Phil Payne
 http://www.isham-research.freeserve.co.uk/quattro
 Phone +44 7785 302803   Fax: +44 7785 309674