[BiturboS4] Abt Chipped car down on expected peformance

Edwards, Dave Dave_Edwards at iOra.com
Mon Aug 12 10:08:21 EDT 2002


Despite what Robin has written, I would be surprised if you just had a
simple air leak as that would affect the overall power of the engine and not
just the peak power. I would have expected you to have noticed it whilst

However it is always a good idea to be familiar with the possible failures
in your car and the TBB split is a common one:
1) Open the hood
2) Take off the engine cover which has "biturbo" on it.
3) The TBB is a black 'rubber' thing right at the front of the engine in the
middle. You should see two plastic pipes coming from the left and right,
rising to meet the TBB where they are clamped to the TBB. These supply the
forced intake air from the intercoolers. The TBB itself is clamped to the
throttle body, a silver metal unit which is itself fixed to the intake
4) Initially run your finger along the fold of the TBB, at the front between
the two pipes (this is just above the crown of the 'fan belt' pulley. It
should be smooth.
5) Shine some light into this area and GENTLY move the top parts of the
plastic pipes away from each other. They won't flex much, but will just
enough to see if the TBB is split.
6) If you still suspect the TBB but can't see any tears then you'll have to
remove it. This is not actually difficult, and APR have instructions on how
to do it on their website (www.goapr.com). It's part of the instructions on
how to install their bipipe. Their bipipe is a metal replacement for the
TBB. I have one myself and can recommend it.

Other hoses can split or separate too. Look at the two which join the air
intake pipes (the silver 'y' piece on top of the engine) to the diverter
valves. Also the short pipes which join the diverter valves to the plastic
pipes which attach to the TBB. Also with a flashlight you can look down near
the back of the headlights and see the intercooler hoses.

Nevertheless, as I started, I expect you to notice an air leak whilst
driving. One thing you notice with a boost gauge, however, is that the S4 is
not on boost except when accelerating hard: Try cruising at say 80kph in 3rd
gear, with your foot enough on the throttle so that the speed needle is just
starting to increase. Then slam your foot on the throttle to the stop. In a
healthy S4 there should be less than a second lag before the torque is felt.
In a chipped S4 this should be really noticable.

Any sort of lag and there is something wrong. Apart from air leaks there is
also the MAF, which could be contaminated and not reading the right airflow.
However I've just looked at your plots and ignoring the Abt chip, your stock
torque curve is very wrong: It gets to around 400Nm at over 3000rpm. It
should be up there from 2000rpm.

If, as it appears, you are not highly technically-minded, then you need to
get your car looked at by someone who knows S4 engines. If this means a trip
to Abt in Germany then I would recommend it.



Message: 3
From: "David" <goodson at menta.net>
To: <biturbos4 at audifans.com>
Subject: RE: [BiturboS4] Re: BiturboS4 digest, Vol 1 #68 - 1 msg
Date: Sat, 10 Aug 2002 12:45:09 +0200

First of all thank you very much to Robin and Dave for such a detailled
answer. To Robin : My S4 is a 1999, with 31000 km, the tuner knows it and
the mod should be the adequate. I'm using 98 gasoline, as the tuner said. I
don't know about Optimax gasoline, I've never seen it in Spain neither in
France. What is the exact role of the Throttle Body Boot? Is there a way to
check its state by myself ? Since it seems that I can't post attachments to
this group, I've made the dyno results available through this link (hope
this works): http://www.audi-sport.net/uploads/74907-David_s4.jpg
It may be important to add that the second test (after mod) have been made
10 months after the first one, with different temperature conditions ( it
was 4=BAc hotter). cheers. David.

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