In a departure from the principle used by Lamborghini, the V10 features petrol direct injection FSI on the Audi models. This combination of ten cylinders and FSI technology gives Audi a unique technological position on the market.

A ten-cylinder engine is the ideal design for realising sporting aspirations. It has the edge on a comparable twelve-cylinder unit thanks to the smaller number of components, resulting in lower moving masses and less internal friction; the fuel is consequently put to very efficient use. A V10 is moreover considerably lighter and more compact than a conventional 12-cylinder engine - including all its add-on components, the engine of the new Audi S6 is just 685 millimetres long, 801 mm wide and 713 mm high. The bare engine measures 560 mm in length.

Although an eight-cylinder engine would be even more compact, to make it into the five-litre-plus class it would need large, heavy pistons and connecting rods, so its ability to rev freely would be impaired as a result. It is no coincidence that many competitors have generally concentrated simply on high torque with their large-capacity V8 engines, rather than attempting to squeeze sporty performance out of them too.

The 435 bhp V10 in the new Audi S6 belongs to the next generation of Audi V-engines, all of which have a 90-degree included angle and a spacing of 90 millimetres between cylinder centres. Its two banks of cylinders are offset by 18.5 mm.

Key areas of the Audi version have been reengineered compared with the engine in the Lamborghini Gallardo. The bore, for instance, has been increased from 82.5 to 84.5 millimetres. Its stroke is 92.8 mm, and its displacement 5,204 cm3.

The crankcase of the Audi ten-cylinder engine is produced by low-pressure die-casting, from a hypereutectic aluminium alloy. This technology renders separate cylinder liners superfluous; the cylinder barrels are instead honed directly from the material by mechanically exposing the hard silicon crystals. A so-called bedplate design - an intermediate frame - gives the crankcase extremely high torsional rigidity and improves its vibrational behaviour. Its cast-in bearing bridges, made from grey cast iron, reduce thermal expansion and keep the amount of play at the main crankshaft bearings within tight tolerances.

The high-strength connecting rods are made from forged steel, and the pistons from an aluminium alloy. At the rated engine speed, each of them covers an average distance of 21 metres per second. With its crankpin offset of 18 degrees, the V10 fires at the ideal spacing of 72 degrees crankshaft angle. A balancing shaft located between the cylinder banks eliminates the free inertial forces of the first degree and also contributes towards the engine's notable refinement.

All four camshafts of the ten-cylinder engine (two per cylinder bank - the DOHC principle) can be adjusted continuously by 42 degrees crankshaft angle via hydraulic camshaft adjusters, depending on the load and engine speed. In this way, filling of the combustion chambers is optimised across the entire engine speed range and the engine response is enhanced.

The camshafts - complete with the balancing shaft, the oil and water pump and the auxiliaries - are driven by maintenance-free chains running on the reverse side of the engine.

The valves - 40 in total - are actuated via roller cam followers with hydraulic valve-play compensation.

The diameter of the valves on the intake side is 32.5 millimetres, and 28.0 mm on the exhaust valves. The highly-loaded exhaust valves are sodium-filled, which ensures a better cooling effect.

The V10 in the new Audi S6 uses the FSI petrol direct injection principle; this permits a high compression ratio of 12.5:1 and a correspondingly effective combustion process.

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