[Germ]

damn,...this is interestin indeed.......makes for good reading !!

cant wait for the day i can afford my b7!! haha

[A4dave]

Germ, me too! me too! Suddenly i realised people who wants to drive an
Audi has to go into their own business....

Oh, thanks for the explanation too Bert...

[DrTT]

KEC,

You mentioned "The other primary concern would be the turbine going into
a very fast backspin at that rpm range. Therefore turbo dies faster."

Are you talking about the DV not being able to cope with the high
pressure (at gear shifts) and therefore causing the compressor side to
run in reverse? If its not the case, please advice. If this is the case,
then I would have thought that the shaft that links the turbine and
compressor would twist (or be subjected to high reverse torque). This can
be solved by a properly set DV (i.e pressure dump/plumb back settings).

On my car, I seem to hit the highest boost (shown on my Defi at about 1.8
bar) at 3500 rpm on 3rd gear. What I found out at the Dyno center was
that mucking about with the DV pressure setting can change the peak
torque between (+-) 30nm! (On my TT, the peak torque changes from 370 to
398nm - at extreme ends of the setting all dyno test were done on the
same dyno, same day, same fuel and almost identical environmental
conditions). So maybe, there is still some "tuning" room in cars already
chipped.

[DrTT]

primus2211,

With reference to the A/F on the dyno chart you posted - isn't it running
a bit rich from 4500rpm (drops from 13 to 11 between 4500-5000rpm) or is
this normal readings for the A4 at full throttle?

I always thought the best place to be at full throttle is high 11's and
low 12's. And much leaner at partial throttle - up to 14.

[DavidT]

KEC,

I'm interested in the scoobie offer only if you're gonna loan it to me..

In your sentence of "turbo going into a very fast backspin". I believe
properly set DV with the right spring setting will solve this, as
mentioned by DrTT. I think you know that's why most of us went
aftermarket on the DVs.

[Weezy]

OOoOOoOoOOiiiitttt cire!!!
dun make fun of jap car owners!!!

[jhlk99]

> Isn't your statement a tad on the contradictory side of things?

No, it isn't. Let me explain.

> The newer units that you'd find at most of the better places would
> include compensation variables in the software that factors in the
> following:
>
> 1) Atmospheric pressure
> 2) Humidity
> 3) Environmental temperature
> 4) Engine load for the calc of the whp (this done by the free rolling
> load test towards the end)

Environmental compensation is straightforward but the last item is the
one that I have most beef with. A free rolling test for drag in no way
allows one to calculate the actual drive-train losses when the engine is
driving the car. There are many losses associated with gears transmitting
power that are not present when the engine is no longer transmitting huge
amounts of power through the transmission. This is affected by how many
gears are present and what configuration the transmission is: FWD, RWD,
AWD. All that the spin-down test measures is the viscous loss + tyres.

The only way for a 4-wheel dynamometer manufacturer to know how to
properly compensate for the above is to take a particular car, test it on
their 4w dyno and then test the engine on an engine-dyno. After that,
they can reliably test the same car on that dynamometer.

I very much doubt that the dyno maker did this for your particular make
and model of car. In practice, they guess the compensation to apply. And
herein lies the crux of the problem. Two different dynos may well have
different guesses built in so the measurements are all very suspect.

Two years ago in the UK, the GT4 Owner's Club organised dyno sessions all
over the country. The same cars were getting different power readings on
different dynos, sometimes on the same day, so that is what I base my
judgement on.

Dynos should only be used for a direct before and after comparison with
all factors kept identical. Even under those conditions, the data is only
valuable as a qualitative tool as the margin of error is still very high.

Tyre rolling resistance can also contribute significantly.

> Apart from that, the only point that I can agree is that different
> engine and different fuel may be a factor.

Fuel and air temperature are critical in a turbocharged car.

Even though we can compensate for air temperature in the dyno, the ECU
compensates for heightened air temperature by dialling back the ignition
timing so power readings go down. You cannot compare the readings if they
are taken on a rainy day and on a 35C day.

Fuel degrades. I cannot testify to the authenticity of the following
information as I did not perform the test myself but someone sent Shell
Optimax for laboratory testing and discovered that the RON drops from 98
to 95 over a period of a few days, at least in that particular sample.
That sort of degradation is going to cost a turbo engine a lot of power.
I do know that my GT4 runs really bad on old fuel.

Jonathan

[Karl_Erik_Chee]

DavidT - I'll try to reach the owner 1st. However, are you in town on
Monday? Best I introduce him to you and if he lends you the car, better
that way.

DrTT - Agree with you on the matter on the DV. But still the backspin
will occur but at what rate only. Hopefully it will not be damaging only.

[Cire]

weezy, no lah...jippie also can go fast fast one...but not in the TRUE
AUDI and VWs forum-lah...I preferred to walk the talk, rather than sayin
one thing and doing the other, righto??

[Cire]

a4force, eh....can't help it man. The B6 looks delicious to eat right now.
It was that faithful day of a wedding and chance meet-up, sigh...a
romantic event, I'll say..
Label it " A Wedding & An Audi "

Hee...hee..he..loan,ah? No lah... why on earth any dealer would want to
lend it out, got back a trashed car, and expects to sell it off as a
relatively new car..????
It will tarnish the dealers' name.


Revo-lution man.!!!!!