Audi RS6 - MTM

Audi RS6
Source: Audi DRIVER
Title: Two of the best
Paul Harris tests two immensely fast RS6s
LIKE the RS4, the RS6 is a gift for the tuning
houses. Why? Because the engine is
turbocharged and this means that remapping the
ECU can push up boost pressures as well as
other factors, giving much greater increases in
output. As well as this, the turbochargers
themselves can be changed or modified to give
the engine different characteristics. The
normally aspirated 4.2 litre V8 engine is
virtually impossible to tune: only 'small
increases in power are possible and then at a
disproportionate price. But the turbocharged
version, currently limited to the RS6 as-far as
production vehicles is concerned, can be uprated
by substantial margins as these tw^o cars from
MTM in Germany and Sportec in Switzerland
show so well.
There are.plenty of uprated RS6s in Britain
already, but it isn't every day that you get your
hands of two of the most outstanding. Both are
magnificent cars and have much in common, but
they also differ in interesting ways. Both were
sprinted down the quarter mile at GTI
International and came within a fraction of a
second of each other, but this sort of margin is
immaterial. These are the fastest accelerating
cars I have driven on British roads. their
immense power and immediate response making
overtaking much safer and dramatically quicker.
Sportec RS550
The output of the Sportec RS 550 engine is 550
PS (407 kW) at 6450 rpm, while maximum
torque is 632 Nm (468 Ib. ft.) at 3400 rpm.
Compare these figures to the normal RS6
engine which delivers 450 PS (333 kW) and
560 Nm (414 Ib. ft.) of torque. With 22% more
power and 13% more torque, the acceleration
of the RS 550 puts the standard RS6 in the
shade.
The increased output has been achieved by
modifications to the tur-bochargers, a revised
air filter and induction system, a new exhaust
system from the pre-catalysts back, and
changes to the engine management system. The
cooling systems for both the gearbox and
engine are modified to cope with the increased
power and torque.
None of these changes alters the docile
character of the RS6 engine. Providing you
don't push the throttle too hard, you would not
know that this is anything other than a smooth,
tractable estate car, apart from the deep bass
rumbling of the exhaust system. Just give it an
extra bit of throttle, though, and the RS 550
rockets away, allowing you to take advantage
of overtaking opportunities which other drivers
could never even consider.
Don't forget that the automatic gearbox of the
RS6 also has its own management unit and this
is also re- mapped by Sportec. The engine and
gearbox ECUs talk to each other and the
standard 'box will change up when a certain
torque level is reached. Re-mapping allows the
gearbox to hold on to a gear until the torque
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has reached a higher level. Apart from improving
the acceleration potential, this also cuts out the
possibility of hunting between gears at certain speeds.
None of this power would be any use without a set of
brakes which match it and, while the RS6 has excellent
brakes with Brembo eight piston callipers and 365 mm
discs at the front, Sportec has developed something
much more powerful. The standard front discs are
replaced by huge 400 mm rotors, virtually filling all
the space within the wheel. At the back, the disc
diameter is 355 mm instead of the standard 335 mm.
The original callipers are used all round, but mounted
on spacing brackets to take account of the increased
disc diameter.
These brakes are absolutely superb, allowing you to
take full advantage of the power of the RS 550. "With
the speed limiting aspect of the ECU disabled, this car
would be able to cruise in Germany at speeds closer to
200 than 150 mph and those massive brakes have the
ability to slow this heavy car without any worries or
drama.
Less impressive was the suspension set-up on this
example. The standard RS6 achieves a very good
balance between handling and ride comfort, but
Sportec was looking for something which shifted this
balance more towards sharp handling. The standard
springs and dampers are replaced by an Eibach
suspension kit, fully adjustable for height. The car had
been heavily laden on the long Journey from
Switzerland, and I felt that the suspension might have
been set high to cope with this, affecting the stability
on high speed curves.

The standard RS6 has a feature which Audi
calls DRC, for dynamic ride control. The
diagonally opposite dampers are connected by
hydraulic lines incorporating valves and the
nett result is that pitching and rolling are
reduced when the suspension on one side of the
car is being compressed. On the Sportec car,
this system had been disconnected because of
the replacement of the original dampers and I
suspect it would have felt more stable on fast
bends if it had still been operational.
The Sportec wheels on the RS 550 have a
diameter of 20-inches and are remarkably light
one-piece forgings. Each weighs only 11.5 kg,
contributing to a very significant reduction in
unsprung weight and improvement in
roadholding. The Continental Conti Sport 2
tyres had a 255/30 section.
This car had some interesting cosmetic
alterations, including a rear skirt made from
carbon fibre and shaped to accept the four tail
pipes and, inside the cabin, aluminium pedals
and foot rest, together with carbon-fibre gearchange
paddles, plus and minus clearly
embossed on their surfaces.
Both of these RS6s are fabulous cars, with
acceleration beyond anything one can
experience with any other conventional road car.
They both demonstrate that this sort of
performance can be achieved without any loss
of smoothness or flexibility. None of these
modifications are cheap, but then we are talking
about a car which starts off at close to .£60,000.
One thing is very clear. Both of these cars have
all the versatility of other A6 Avants, practical
and capable of carrying big loads, and no other
car can come near them in terms of practicality
and hyper-performance.
RS6-MTM
The output of the MTM modified RS6 engine
is rated at 535 PS (393 kW), a little lower than
that of the Sportec RS 550, but, at this level,
the difference is not very significant. This
Stage 3 conversion involves replacing the
down pipes from the exhaust manifolds, a job
which involves removal of the engine and so
the labour cost is quite high. Perhaps more
significantly, the maximum torque is 720 Nm
(533 Ib.ft.) at 3160 rpm, while the power peaks
at ^SSO rpm. The power of the standard RS6
engine is achieved at 5700 rpm and then
remains level before falling away at 6400 rpm.
MTM uses a complex exhaust system which
does away with the primary catalytic
converters and replaces the main converters
with 100 cell units. Like the RS 550
conversion, it ends with four pipes, but the
outer pair incorporate vacuum controlled flap
valves, a system which Audi already uses for
the TT 3.2. At normal throttle openings, the
flap valves remain closed and the exhaust
sound is quite muffled but, when the
accelerator pedal is opened enough to increase
the boost pressure, the vacuum unit opens the
valves. The result is a magnificent crackle,
almost like that of a vintage formula racing car,
as the car accelerates away. As soon as the
boost drops, the flap valves close to reduce the
sound level and, when the engine is switched
off, they open to relieve any pressure in the
system.
Fuel consumption? With either car, reckon
on an average of around 18-19 mpg on British
roads, using plenty of opportunity to exercise
the engine's potential. Higher cruising speeds
and greater use of the acceleration will knock it
back to about 16 mpg hut, on the other hand,
driving it quietly can return just over 20 mpg.
Both cars need 98 octane petrol so, in this
country, you will need to seek out Shell
stations to fill up with Optimax.
Bear one important point in mind. The RS6 is a
very heavy car, weighing in at 4112 Ib.
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Much of the improvement in output comes from remapping
the engine ECU, permitting a maximum
boost pressure of 2.31 bar. The gearbox ECU is also
re-mapped to prevent hunting between gears at certain
speeds.
Unlike the Swiss car, the suspension of the MTM
RS6 was completely standard. Although this might not
be the ideal set-up for competition, it provides a
comfortable ride and considerable stability in curves.
Audi's DRC system certainly works well and the
MTM car shows that the standard suspension is ideal
for road use, even when the power is boosted to such a
high level.
The MTM brake conversion is less radical, the front
discs increased in diameter to 380 mm, again in con-
junction with the standard 8-piston Brembo callipers.
Although this set-up may not match the 400/355
combination at very high speeds, I found that it could
cope powerfully with any braking conditions likely to
be met on the road. Kim Collins at qst, the British
importer for MTM, considers that the Mov' It brake
conversion is superior. This has 380 mm front discs,
with 6 rather than 8-piston callipers, but the 6 gives a
greater pad area. Mov' It also has a 342 mm rear brake
set-up with 4-piston callipers and separate handbrake
callipers.
The wheels, 9.5 x 19-inches, are unique to MTM
and, on the test car, were shod with 275/30 Pirelli P
tyres.
unladen. Modest increases in power will have little
effect on its acceleration and it is only by increasing
the output by big margins that the tuners are able to
make significant improvements to its performance.
Both of these cars will accelerate from rest to 60 mph
in less than 4.5 seconds, and ungoverned, will
probably achieve close to 200 mph, should the
conditions ever permit.
Both MTM and Sportec have agents with excellent
reputations in this country. MTM is handled by Kim
Collins qst in Sussex, while Sportec is imported by
AmD in Bicester. II

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