Audi is developing a new twin-turbo system which uses an electrically-driven turbocharger in conjunction with a conventional turbocharger to eliminate off-throttle turbo lag.
Conventional turbochargers rely on exhaust pressure to deliver boost - which is only generated as revs climb - producing a fundamental element of turbo lag from idle.
Turbo lag has been greatly reduced during the turbocharger’s 50-year automotive history, but the advent of the electric turbocharger promises to eradicate it altogether.
In using an electric motor to spool up a small turbocharger in readiness for throttle application, the new system can potentially provide the solution to that 'hole' - where nothing happens momentarily - with an exhaust-driven turbo or mechanical supercharger.
As revs and exhaust pressure climbs, the larger second turbo takes over to cover the remainder of the engine’s rev range - while the electric turbo is bypassed and disengaged.
Audi has compared the performance of prototype engines with conventional twin-turbodiesel models and claims that the new system can yield a two car-length advantage in the first three seconds of acceleration.
This would offer more predictable overtaking and incidental acceleration, but also benefit fuel efficiency and emissions.
Audi’s current prototypes are based around a 3.0 litre turbodiesel V6 engine, but the technology could benefit a range of capacities and configurations.
Electric turbo technology is also being explored by other manufacturers, with industry whispers suggesting that BMW will employ such a system for the rumoured tri-turbo arrangement in the upcoming M3/M4 performance models.
BMW already holds patents for such technology, and Subaru is also said to be exploring similar systems.
Audi could well be the first to bring the technology to market. Although it remains unclear which model will debut the tech, with the new-generation A4 due in 2014 is a possibility.
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