Audi’s new 4.0 TFSI engine in detail

Article by Christian Andrei, on September 16, 2011

Audi is adding a new, high-performance gasoline engine to its lineup. The 4.0 TFSI has an output that ranges between 309 kW (420 hp) and 382 kW (520 hp) and could have up to 650 Nm (479.42 lb-ft) of torque. This engine is used in slightly varying configurations in the S6, S6 Avant, S7 Sportback and S8. The new V8 is a highly advanced engine that has many innovative solutions.

The 4.0 TFSI is the latest member of Audi’s lineup of V engines and has all of this range’s typical traits. Its cylinder angle is the usual 90 degrees. To save on space, the chain drive for the four camshafts and ancillary units is positioned at the back.

Its cylinder case is a cast aluminum-silicon alloy. The weight of this eight-cylinder unit is very low. It also has a very compact construction that resulted to its length getting cut to 497 mm (19.57 in). Audi’s FSI direct injection system is used for the fuel.

For better combustion, it has switchable flaps in the intake ports that lead to a rolling type of movement in the incoming air. Similar to nearly all Audi engines, this new 4.0 TFSI uses the downsizing principle where forced induction replaces displacement.

The intake air is compressed by one turbocharger per cylinder bank. It is called twinscroll technology, where the exhaust flows to the turbine wheel at high speed via two separate ports. As a result, torque is developed very early, at just above idle. The two turbochargers and the intercooler are placed in the inside V of the cylinder banks instead of in the typical location outside next to the crankcase.

Audi built the cylinder heads innovatively. Its exhaust side is on the inside while on the outside, we see the intake side. This layout allows for compact dimensions and short gas paths with very little flow losses. In addition, the 4.0 TFSI responds instantly to the gas pedal. The thermal conditions in the inside V are stabilized by the sophisticated insulation of the hot components, specifically the exhaust manifold.

As for the chassis, the new Audi S8 luxury sedan is provided with a specially tuned adaptive air suspension with variable damping. This could modify – in three levels -- the ride height of the body for a wide-ranging driving experience. Interestingly, this complements the S8’s dynamic steering that could adapt its steering ratio and boost according to vehicle speed. This dynamic steering employs slight, nearly imperceptible steering corrections in order to stabilize handling during cornering.

The adaptive air suspension and the dynamic steering systems are just two of many elements included in the Audi drive select dynamics system, along with the eight-speed tiptronic, engine management and the sport differential. A driver could tweak the functions of these elements by selecting from among the available five modes: comfort, auto, dynamic, individual and efficiency. The new 5.15 meter-long (16.90 ft) Audi S8 luxury sedan sits, as standard, on 9Jx20 S-specific wheels wrapped in 265/40-series tires. Five optional wheels are available, four of which feature a 21-inch diagonal.

Braking is handled by four internally ventilated disc brakes that measure 400mm (15.75 in) on the front and 365mm (14.37 in) at the rear. S8 logos are featured on the front matt black calipers. Optional brake discs made from carbon fiber-ceramic discs – with anthracite gray calipers – could also be availed, each lighter by five kilograms (11 lbs) than the standard discs.

In addition, the S8’s ESP stabilization program features a sport mode, which allows drivers to determine the engine output through the position of the pedals. With a really low weight of just 1,975 kilograms (4,354.13 lbs), the new Audi S8 luxury sedan offers a decisive performance on a higher level. This is thanks to the fact that its Audi Space Frame (ASF) body is made mostly from aluminum, with only the B-pillars crafted from ultra high-strength steel.

As a matter of fact, the body of the new Audi S8 features a weight of 231 kilograms (509.27 lbs), which is around 100 kilograms (220.46 lbs) lighter than a conventional steel construction. Furthermore, Audi’s ultra-lightweight construction allowed weight to be reduced in other sections of the S8, like its chassis. A number of details distinguish the S8 from other models in its range. For instance, it features a single-frame grille in platinum gray and eight double bars in chrome.

Moreover, its side air intakes feature high-gloss black slats and aluminum-look ribs while an aluminum-look blade renders the bumper look sharper. On the other hand, the sides of the new Audi S8 are laden with body-color trim strips, particularly on the door handles and sills, while mirror housings donning a polished aluminum-look.

In addition, the rear diffuser insert features a blade with a two-layer aluminum-look that provides a contrast to parts finished in platinum gray. The rear end is completed by chrome-look dual oval tailpipes. Of course, the new Audi S8 features S8 or V8 T badges on the front, back and sides. Customers could have their new Audi S8 finished in any of the 13 available colors. Two of these colors -- Daytona Gray and Prism Silver -- are exclusive for the Audi S8.

Topics: audi, engine

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