The New Audi S4/S4 Avant

by LhYnxz Mon Sep 22, 2008 6:55 pm

The New Audi S4/S4 Avant

Source: Audi AG

Three-liter V6 unit generates 245 kW (333 hp)

Acceleration from 0 to 100 km/h in 5.1 seconds

Average fuel consumption of just 9.7 liters

Ingolstadt - Audi is introducing its new sporty top models in the
midsize class - the S4 and the S4 Avant. Their engine, a three-liter V6
with direct fuel injection and mechanical turbocharging, delivers a
powerful 245 kW (333 hp). It accelerates the S4 to 100 km/h (62.14 mph)
in just 5.1 seconds, but on average only uses 9.7 liters of fuel per
100 km (24.25 US mpg). The quattro permanent all-wheel drive system
transfers its power to the road in style, which is then converted by
the sport suspension into dynamic handling. Upon request, Audi can
equip the new S4 and S4 Avant with innovative technologies that further
increase their lead over the competition. The seven-speed S tronic
changes gears with lightning speed, and the new sport differential
distributes the torque as needed between the rear wheels. The new Audi
S4 will be unveiled to the public for the first time at the Paris Auto
Show from October 2 to 19.
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The heart of the new S4 and S4 Avant is a completely redesigned
engine. The 3.0 TFSI, the newest member of the Audi V-engine family, is
an outstanding example of how the brand with the four rings blends
performance and efficiency. The V6 generates its power from a
displacement of 2,995 cc, is equipped with a supercharger, and delivers
245 kW (333 hp). The sedan sprints to100 km/h (62.14 mph) in just 5.1
seconds, and the Avant in 5.2 seconds: they both have an electronically
governed top speed of 250 km/h (155.34 mph).
The "T" in the 3.0's TFSI nomenclature no longer merely stands
for "turbo", but rather for the concept of supercharging in general –
extensive testing on the big V6 has proven the superiority of
mechanical charging. In conjunction with direct injection it is far
superior to twin turbochargers, both in terms of packaging and of
starting performance and responsiveness.
The compressor is so compact that it easily fits inside the
90-degree V of the cylinder banks, in place of the intake manifold. Two
four-vane rotary pistons counter-rotate inside the turbocharger at up
to 23,000 rpm. Two charge-air coolers are integrated into the housing
and are connected to a separate coolant circuit. An impressive array of
measures keeps the noise generated by the compressor to a minimum.
The engine-driven belt that powers the mechanical charger
provides full thrust right from idling speed. The 3.0 TFSI delivers its
maximum 440 Nm (324.53 lb-ft) at 2,500 rpm and maintains this
constantly until 4,850 rpm. In fourth gear, the vehicle accelerates
from 80 to 120 km/h (49.71 to 74.56 mph) in just 4.4 seconds. Thanks to
the extremely short gas paths, the sonorous, supercharged V6 responds
spontaneously to the throttle, even more so than a naturally aspirated
engine of the same displacement.
Furthermore, the new 3.0 TFSI achieves exemplary fuel
efficiency. On average, the sedan uses 9.7 liters of fuel per 100 km
(24.25 US mpg), and the Avant 9.9 liters per 100 km (23.76 US mpg) – an
improvement of 3.4 liters (26 percent) compared with its predecessor.
The Audi technology of gasoline direct injection was what made this
great efficiency possible in the first place. Unlike conventional
concepts, it allows the compressor to be located behind the throttle
valve. In view of the low density of the intake air at loads below
supercharging level and when coasting, its rotors are free-running and
the amount of power required to drive them is low.
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Dynamism and efficiency: The new seven-speed S tronic

The V6 power in the new S4 and S4 Avant flows into a six-speed
transmission, fitted as standard, which shifts quickly and precisely.
As an option, Audi offers a state-of-the-art dual-clutch transmission –
the seven-speed S tronic is extremely dynamic and highly efficient. The
driver has the option of driving in fully automatic mode or selecting
the gears with paddles on the steering wheel or directly with the shift
lever – all of which provide impressively quick gearshifts. The
gearshift feel is dynamic, comfortable and very precise – typically
Audi.
The seven-speed S tronic consists of two separate transmissions
and uses two multidisk clutches that control the various gears. The
large K1 clutch guides the power via a solid shaft to the pinions for
gears 1, 3, 5 and 7. A hollow shaft rotates around the solid shaft; it
is connected to the compact K2 clutch, which is integrated within its
larger counterpart and controls the pinions for gears 2, 4, 6 and
reverse gear.
Both transmission structures are continuously active, but only
one is powered at a time by the engine. For example, when the driver
accelerates in third gear, the fourth gear is already engaged in the
second transmission structure. The shifting process takes place as the
clutch changes – K1 opens and K2 closes with lightning speed. This
process takes only a few hundredths of a second and is completed
without interrupting traction. It is so comfortable and smooth that the
driver hardly notices it.
The seven-speed S tronic is designed for maximum efficiency. It
operates with very high efficiency and its intelligent control system
maximizes fuel economy in automatic mode. With its wide gear ratio
spread of 8.0:1 the seven-speed S tronic easily exploits the tremendous
power and superior torque of the 3.0 TFSI.
The quattro permanent all-wheel drive system transfers power to
the road with supreme ease. Under regular driving conditions, it sends
40 percent of its torque to the front wheels and 60 percent to the rear
wheels – a slightly rear-biased, sporty characteristic. Where
necessary, it can vary distribution within fractions of a second.
The quattro drive system ensures safe self-steering
characteristics, high stability and excellent traction in comparison
with rear-wheel-drive competitors.
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Customized torque distribution: The sport differential with Audi drive select

The new, active sport differential ideally complements the
quattro drive system and lends it even greater fascination. When the
steering wheel is turned or the car accelerated in a corner, power is
redirected in a controlled manner to the outer rear wheel, literally
pushing the vehicle through the corner. The system intervenes to
counter any signs of understeer or oversteer. For the driver, this
means reduced effort at the steering wheel and even higher lateral
acceleration.
The active sport differential is a new type of rear-axle
differential. A superposition gear was added to both the left and right
sides of the classic differential; it rotates ten percent faster than
the wheel's drive shaft.
Both components can be connected through a multidisk clutch,
which runs in an oil bath, and is operated by an electro-hydraulic
actuator. In most driving situations, the clutch can divert almost the
complete input torque to one wheel in this way.
Controlled by an array of sensors and a high-speed computer,
the active sport differential needs less than 100 milliseconds to
redirect power. Drivers can adapt their manner of driving, along with
characteristics for the load changes, to three performance maps. Unlike
competitors' systems, the Audi sport differential is just as effective
when the engine is driving the wheels as it is on the overrun or when
the car is coasting freely.
The new Audi S4 and S4 Avant are well-trained athletes. Their
five-link front axle and the self-tracking trapezoidal-link rear axle
are of a highly sophisticated design; both axles are made almost
entirely of aluminum and are therefore very lightweight. The
low-mounted steering gear transmits the steering forces to the wheels
without any lag time and gives the driver a precise and sensitive road
feel.
The spontaneity of Audi's new midsize athletes is fascinating,
and they possess the precise reactions of a thoroughbred sports car. In
these transmissions, the differential is positioned in front of the
clutch, which made it possible to move the engine 154 mm (6.06 in)
forwards compared with the predecessor model. This unusual layout
perfectly evens out the axle loads, and also affords the long wheelbase
of 2,811 mm (9.22 ft) exceptional stability.
The chassis of both new S models received stiffer axle
bearings, and the sporty tuning with stiff shock absorbers puts the
chassis 20 mm (0.79 in) closer to the road. Huge high-performance and
fade-resistant brakes sit behind the 18-inch and optional 19-inch cast
aluminum wheels. The black-painted brake calipers – at the front with
the S4 logo – grip the ventilated disks with newly developed brake
pads.