A senior Audi engineer intimately involved in the project confirmed to Wheels that the four-ringed brand is working on a new twin-turbo 4.2-litre V8 that, in his words, "will be absolutely the world's best".

Rumours that Audi is developing a new twin-huffer, petrol-fed V8 have been circling for some months now, but, speaking on the condition of anonymity, the German engineer revealed some key details of the project exclusively to Wheels. It's believed the new engine will debut in the next-gen RS4, due early in 2011, and will also power the R8 when its first mid-life update arrives sometime later in 2011.

The new powerplant is a thorough evolution of the current 4.2-litre V8 that currently powers the S5 coupe and electrified the previous-gen RS4. Despite running the same bore centres and bore and stroke (84.5mm x 92.8mm) as the current mill, every component has been redesigned or upgraded and the entire valvetrain assembly and intake system has been designed from scratch to accommodate the sequential twin-turbo system.

Wheels understands several different tunes will be delivered; including an approximately 310kW version for the A8 limo and a 340kW version for the next RS4. Whether this new forced-fed V8 will replace the Lamborghini-derived V10 currently powering several high-end Audi's is unclear at this stage.

A more official (although tentative) confirmation of the new engine program came from an exclusive interview with the VW Group's powertrain chief, Wolfgang Hatz, at last week's Frankfurt motor show.

Asked when the world will see the new twin-turbo V8, (cue a heavily pregnant pause and nervous sideways glances from the PR minders present) Dr Hatz's answer was "... that will take a little more time, but I can say that it will not be next year ... but it will be a great engine."

Hatz also wouldn't be drawn on which specific models the new engine will power. When asked whether Audi will adopt a similar strategy to BMW's twin-turbo, 4.4-litre V8 in placing different tunes of the engine in various models, a knowing smile and a deadpan "we have several solutions" was the only answer forthcoming.