[BiturboS4] Abt chipped car down on expected performance

Edwards, Dave Dave_Edwards at iOra.com
Thu Aug 22 12:09:46 EDT 2002


What you describe first sounds normal. When you are holding the car off
acceleration but at speed, the turbos are still pushing the air to the
throttle, but it is only partially open. As a result the diverter valves
open and the air recirculates. When you then accelerate (probably quite hard
as you've been waiting to overtake), the throttle opens quickly, and then
the diverter valves close, but only after a finite delay. This delay is
enough to cause the 'shock' you describe (as I have understood your
The second is more difficult. Certainly at low revs with the window down you
will hear some of the normal workings of the engine. For example when you
change gear you should hear a quick 'whoosh' as the diverter valves open. If
it is significantly loud, and not just a whoosh, then perhaps something is
wrong. As I have written, your dyno plots don't look right to me and you may
have an air leak somewhere.


P.S. My car's at the tuner today, primarily to have the full Miltek system
fitted. I'll have the dyno results tomorrow (although I probably won't post
'till next week as I'm going on a short vacation - taking my daughter to
Disneyland Paris :-)

-----Original Message-----
From: David [mailto:goodson at menta.net]
Sent: 21 August 2002 11:10
To: biturbos4; Edwards Dave
Subject: RE : Abt chipped car down on expected performance

Thanks again for the advises. Since I'm on holidays, I couldn't answer to
your mail before. I will try to have a in-depth look to the engine. If I
find anything, I will let you know. I hope I won't have to go to Germany to
have it checked. Or this Abt mod will be the most expensive mod ever done.
Maybe I will try to convince my Audi workshop here in Barcelona to
investigate it. But obviously, it won't be easy to explain to them that
"this car I didn't buy to you and witch has been chipped by another workshop
in France is working good, but I suspect that if should work even better,
can you fix it please?". We'll see. I noticed a couple more of interesting
symptoms : One is old (from the first day I had the car, I guess, but I
didn't notice it) : Let's say your driving on a highway, and a car on your
lane forces you to slow down. You shift from 5th to 4th (or 4th to 3rd) and
maintain the car without accelerating until the guy in front moves away to
let you pass. Then, when you accelerate again there is some king of little
"shock" you can feel when your engine passes from retaining the car to
accelerate it. It happens anywhere between 2200 and 3500 rpm. The sensation
is subtle and difficult to reproduce on demand, something like a very short
cut of ignition. The other thing is newer, it's a subtle sound ( like a
small air escape in the exhaust, or some vibration in the exhaust),
noticeable at low rev when the window is open, specially when the rev are
going down. The pity is that despite these little problems, the car is
working good. I probably wouldn't have noticed it if I was not investigating
the "strange" dyno results I had after chipping. cheers. David.

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