[s-cars] Low boost on 1995 S6 (insert swearword of your choic e)

[Paul Heneghan]

Many thanks for that info, Feico.

There is some doubt as to whether the meter is reset to 1.0 when the engine
is not running, but it sounds as if you have seen different numbers
depending on atmospheric.  I've only ever seen 1.0, but we haven't had any
tropical storms or exceptionally fine weather recently.

The latest in my max boost problems:

In August, during our heat wave, I was regularly seeing 2.1

Now that the temperature is dropped to the 0 - 10 range, there have been
some days when I have been unable to achieve more than 1.7.  However,
yesterday when we had a temporary warm spell (10 - 15) I did get a momentary
1.9.  Maybe I shouldn't be worrying after all.  The other problem, is that
I'm getting used to the acceleration.  Having driven an 80q (135hp) for 12
years, I was awestruck when I first experienced the turbo boost of the S6.
Now, maybe, I'm taking it for granted.

The other factor that needs to be taken into account is the RON of the
petrol.  I'm using 97 RON at the moment, but other local turbo enthusiasts
claim that 97RON from one petrol supplier is not as good as 97RON from
another.  I can't get 98RON anywhere - I'm making half-hearted enquiries
into obtaining toluene, but no suppliers are answering my emails.

I'm still going to check out my hoses and vacuum connections this weekend to
see if there are any culprits there.  Unfortunately, I'll have to wait about
a month before I get my VAG-TEC to pull the codes.  I'll try installing the
checklight, but I don't expect it to work as the bulbs in that region don't
pick up thier drive from the PCB, but are direct wired - and there's no
connection for a check light.

I hadn't realised that max boost would be temperature related.  In fact,
I've heard so many reports about turbos performing better in the cold, that
I was half expecting to see more boost - stupid of me, because the cold air
(for the same boost) has a higher O2 content, so extra boost would be
undesirable (from an engine longevity poit of view).

My Bentley (CD-ROM) is part way through being ordered.  I can't wait!

Paul

> -----Original Message-----
> From:	FvAMI at aol.com [SMTP:FvAMI at aol.com]
> Sent:	Tuesday, October 15, 2002 4:55 PM
> To:	paul.heneghan at bbc.co.uk
> Cc:	s-car-list at audifans.com
> Subject:	Re: [s-cars] Low boost on 1995 S6 (insert swearword of your
> choice)
>
> From the Bentley manual Deg. C
>
> Altitude                                Temperature (outside)
> Meters         -10 to 0       0-10     10-20    20-30    30+
> 0-1800         1.808          1.939    1.995    2.016    2.054
> 1800-2300    1.707          1.824    1.877    1.897    1.932
> 2300-3000    1.585          1.700    1.749    1.768    1.801
>
> To check the accuracy of your meter (to within 0.1 bar) measure the
> barometric pressure and turn your ignition key to the on position and
> compare the results. I find mine to be off by 0.05 to 0.10 bar too high.
> At 990 mb it reads 1.0 which is correct but at 1020 mb it reads 1.1
>
> This is a function of
> 1) Component tolerances
> 2) The voltage supplied to the MAP in the Motronics unit being independent
> of the one being supplied to the in dash meter providing the reference
> voltage.
> 3) Anything better than +/- 10% is acceptable.
>
> Best regards,
> Feico van der Laan


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