Audi RS5 diesel driven

30 May, 2014 4:30pm David Vivian

Clever electric turbo gives Audi’s first-ever RS-badged diesel petrol-like responses

Audi has given Auto Express a tantalising glimpse of what might, in the near future, become the basis for a range of high-performance turbodiesels aimed squarely at driving enthusiasts. And the 380bhp, 174mph RS5 TDI-e Concept previews what could be the 
first diesel Audi to wear an RS badge.

Under the bonnet is a heavily boosted version of the next-generation 3.0-litre V6 TDI biturbo, complete with ‘e-booster’ technology that contributes towards the thumping 750Nm of torque, developed from just 1,250rpm.

With a claimed 0-62mph time of four seconds and a 174mph top speed, the performance certainly seems worthy of RS status. The purpose of ‘e-boost’, a small electrically driven blower plumbed in between the intercooler and the induction system, is two-fold.

Even diesel engines with two-stage turbos – the smaller turbo spinning up more rapidly to generate boost at lower revs and smaller throttle openings before the larger unit shoulders the workload – can suffer from a momentary dead spot when pulling away from rest due to the mass inertia of the turbocharger impeller.

The electric turbo gets this spinning rapidly before the hot exhaust gases can do the job effectively, giving more immediate throttle response away from rest and eliminating off-boost lethargy when you get back on the throttle at, say, the exit of a bend.

Audi RS5 diesel rear static

The system operates up to 3,000rpm, at which point it’s no longer needed and bypassed completely.You might think a diesel ‘RS5’ would struggle to live with a 552bhp RS6 Avant pace car being pushed hard by a pro driver around the twisty 2.1-mile Audi centre handling circuit. Think again.

The striking thing is how easy it was. The deep bass of the exhaust note may be artificially enhanced, and sounds more V8 than V6, but it’s entirely in keeping with the effortless way the RS5 TDI-e piles on speed, riding a seemingly endless wave of torque that punches the car out of slow bends with a ferocity not even the RS6 can match.

Although peak power is developed at a modest 4,200rpm, all of the engine’s prodigious torque is available from just over tickover and Audi’s superb eight-speed auto box keeps the action flowing.

Twenty five years after producing its first diesel, Audi’s commitment to the future of this engine tech is obvious.

The RS5 V6 TDI-e proves that diesel is a viable alternative to petrol power for the sportiest Audis and that ‘e-booster’ electric turbo tech brings significant gains in throttle response and driveability. We’re looking forward to the first production diesel RS, which could arrive as soon as next year.