[BiturboS4] Re: BiturboS4 digest, Vol 1 #68 - 1 msg

Robin St.Clair uberseehandel at yahoo.com
Fri Aug 9 12:36:52 EDT 2002

[ Picked text/plain from multipart/alternative ]

You have stumbled upon the inherent problem with chassis and in car dynamom=
For now we wil leave 'in-car' dynos out of it, purely accelerometers. The c=
hassis dyno measures power at the wheels, the manufacturer advertises brake=
 horse power. What is measured on a dyno is the power at the wheel after sl=
ippaqge, transmission loss and all the various factors to do with the adequ=
acy or otherwise of delivering appropriate amounts of air to the car's radi=
ators, intercoolers and air intakes, maintaining proper temperatures and ke=
eping the car on the dyno under power.
Basically what the dyno operator does is run the car and, using the measure=
d torque and the published power figures, calculate what the power loss is.=
 Then after making the modification, another run is made and the power reca=
lculated using the previously calculated power loss percentage. Read my lip=
s - its all smoke and mirrors.
Firstly, what power does your car actually develop in stock trim - 350NM, 3=
70NM, 395NM or 420NM, well for a euro car, the estimate is 395, but your ca=
r could be different.
Secondly, what about wheels slip - I know shops which fit slicks to cut dow=
n on on power loss, not all do, and as temperatures risre, so the tyre's st=
ickiness changes, heat in the tyre is power loss.
I could go on, but to cut to the chase, use a dyno to measure the differenc=
e in power before and after a modification, this is all you can reasonably =
As far as the 'dissapointing' performance is concerned, what fuel are you u=
sing, is the chip designed for it? What is the state of your Throttle Body =
If you visit the Abt web site, you can find the power curves for their chip=
 on the S4, you will see that it is quite different from the figures your F=
rench friends quoted.
I would take my car to a shop with a rollong road and retest it with the or=
iginal chip and then reinswtall the Abt xhip, run a throttle adaptation, an=
d remearue, doc not adjust the figures for "brake" horsepower, just look at=
 the difference.
It really helps with a turbo not to let the intercoolers get heatsoaked and=
 to use Optimax gasoline.

From: "David"
Date: Fri, 9 Aug 2002 10:00:51 +0200
Subject: [BiturboS4] Abt modification - first impressions

This is a multi-part message in MIME format.
I had my Baby modified with the basic 310 hp/500 Nm Abt program three weeks
ago. I live in Spain, but the Abt representative here was out of order, so I
had to go to France (to Viacom Abt, only importer in France) to have the job
My impression about the French company is good : they seems to be serious
people, with a nice and clean workshop and they take time to talk with
clients. I brought my car in the morning, spent half an hour to chat with
the technician, and went back in the afternoon to pick up the car and spent
another hour chatting with him. we had a 20 minutes test drive together too
after the mod.
My first impression about the mod is :
Is that all ?
Yes, it pushes a little bit more, but for 2400 Euros (which was about 2400 $
at this time) I was expecting something more... spectacular.
I asked them to measure the power and torque before and after modification,
and they did it with an "on board" dyno system (on a freeway) since they
don't have a static dyno rolling road. They told me the figures was not
absolutely precise, but the difference between the "before" and the "after"
figures could be trusted. The results are the following :
Before mod : max power : 266.9 hp at 6090 rpm and max torque :38.19 mkgF at
3801 rpm.
After mod : max power : 317.6 hp at 5530 rpm and max torque :47.83 mkgF at
3981 rpm.
which means a gain of 50.7 hp and 9.64 mkgF.

Since I've had a real dyno rolling road test here in Spain a few months
before, when I came back I took the car to the same place and did another
test. The results are less optimistic :
261 hp / 418 Nm before mod, and 303 hp / 432.8 Nm after mod.
Temperature was 4=3DBAc higher on the second test.
I'm attaching to this mail the graphs of this test (before and after mod). I
have photoshoped them a little so you can see before and after on the same
Question for the specialists around : what are these little "accidents" at
the beginning of both curves (at around 1000 rpm for torque and 35 km/h for
Shouldn't torque be higher after modification ? (the gain is only 15 Nm).
Comments welcome.
Next time I will tell you about my new Stratmosphere short shifter.

[ power.jpg of type image/jpeg deleted ]
[ torque.jpg of type image/jpeg deleted ]

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