The RS5 TDI Concept utilises a 3.0-litre diesel V6 engine, which in addition to two turbochargers also uses a third, electrically driven compressor that mimics a turbo to compress air and send immediate boost to the engine off idle.
The compressor works off a 48-volt electrical system – four times that of a regular petrol RS5 – and completely uses regenerative energy stored in a boot-mounted lithium-ion pack to work like an additional turbo.
Its application means Audi engineers can use larger turbos to create more top-end power without suffering low-end turbo lag.
The RS5 TDI Concept produces 283kW of power at 4200rpm, and 750Nm of torque between 1250rpm and 2000rpm. Compared with the 4.2-litre petrol V8 in the production RS5, the TDI Concept makes 48kW less but 320Nm more. An eight-speed automatic replaces the seven-speed dual-clutch transmission, but drive to all four wheels is retained, and a claimed 4.0-second 0-100km/h for the V6 TDI is half a second quicker than the petrol V8.
In the RS5 TDI Concept, the compressor provides maximum boost in just 250 milliseconds after the throttle has been pressed, at up to two seconds at a time below 3800rpm, at which point the larger mechanical turbos fully take over.
Audi has confirmed the system “represents the first step in Audi's electrification of the TDI” in production vehicles.
“The new hybridisation components will soon be launched on the market,” it asserted in a statement. “In the future there will be a tailored solution for every customer and requirement, up to and including a TDI with plug-in hybrid technology.”
Audi V6 TDI development manager Sven Beechle also confirmed that the Audi RS5 Concept drivetrain is “basically for production” and that there is a “good chance to see it in near future”.
Pressed for dates, Beechle replied: “Wait and see, next year is a nice year…”
Although sports cars are prime candidates for what the development manager describes as an “emotional” diesel drivetrain with “direct step off”, he also asserts that the mild hybrid is “a technology you can combine with all type of cars.”
With Audi launching a new-generation Q7 later this year, a mild hybrid version utilising the RS5 Concept drivetrain could complement the Q7 e-tron already announced for production. The next-generation R8 sports coupe due next year could be another candidate for the electrification of diesel.