First drive: Audi A6/A7 twins now quickest diesels in Oz

AUDI’S new 230kW/650Nm 3.0-litre bi-turbo V6 diesel engine has debuted in Australia, delivering class-leading torque output and enabling the A6 sedan and A7 Sportback to out-punch yet undercut oil-burning rivals from BMW and Mercedes-Benz.

The Ingolstadt-based company expects the new TDI Biturbo (BiTDI) to attract new customers and account for around 15 per cent of A6 and A7 sales in Australia, where more than half of A6 models sold in 2012 were diesel.

Representing flagships of the mainstream A6 and A7 ranges (V8 S models excluded), the new BiTDI variants are Australia’s fastest-accelerating diesel cars, with 0-100km/h times of 5.1 and 5.3 seconds respectively.

They are not far off the times posted by the S6 and S7, which deploy a turbocharged 4.0-litre petrol V8 pumping out 309kW and 550Nm for a sprint time of 4.6s in the S6 and 4.7s in the S7, both of which are significantly more expensive to buy and to fuel.

The nearest diesel rival for standing-start acceleration is the 230kW/630Nm BMW 535d, which cracks triple digits in 5.5s but is $2700 more expensive than the A6 BiTDI, which costs $118,800 plus on-road costs.

A rival to the A7 BiTDI is harder to find in Australia as there is no diesel-engined BMW 6 Series Gran Coupe, the BMW 530d Gran Turismo is not in the same power league and the 195kW/620Nm Mercedes-Benz CLS350 CDI takes almost a whole second longer to 100km/h – while costing $10,600 more than the A7’s $148,600 sticker.

Drivers looking for the ultimate blend of performance and diesel efficiency may look at the BMW 535d, which consumes 5.6 litres per 100 kilometres on the combined cycle, whereas the A6 and A7 BiTDI both use 6.4L/100km.

Benz is also slightly more economical than Audi, trading performance for efficiency at 6.1L/100km for the E350 CDI sedan ($135,485) and 6.2L/100km for the CLS 350 CDI.

Both Audis feature quattro all-wheel-drive, eight-speed automatic transmissions with paddle-shift, and fuel-saving idle-stop and regenerative braking systems.

Audi claims the engine’s technology has been bred from its Le Mans-winning diesel racing cars.

Two turbos separated by a valve are used in series, a small variable-geometry unit providing boost at low revs and a larger one providing pre-compression until a valve starts to open at 2500rpm, allowing it to take over.

Redlined at 5200rpm, the engine develops peak power between 3900 and 4500rpm (when only the big turbo is operating), while maximum torque is delivered between 1450 and 2800rpm.

Reminding the driver of the engine’s performance edge is a speaker built into the exhaust designed to deliver a “rich and meaty tapestry of sound” from the presumably otherwise aurally uninspiring diesel V6.

The next Audi to receive this engine in Australia will be the SQ5 SUV – the brand’s first diesel S model – that arrives in April.

Befitting high-end performance variants, the A6 and A7 BiTDI are specified with premium Bose surround sound audio systems, Bluetooth streaming, satellite navigation, parking sensors with reversing cameras, Xenon headlights, keyless entry and start, leather upholstery with electric front seat adjustment and driver’s side memory, and an electric glass sunroof.

While the A6 gets 18-inch alloys, the A7 has 19-inch rims (a $1930 upgrade on the A6) and extra equipment including quad-zone climate control ($1390 extra on the A6), premium Valcona leather (a $700 option on the A6), dual front cameras that help the driver see around corners when emerging from junctions, and an electric tailgate.

However, the A6 has the S line exterior styling package as standard (the equivalent A7 upgrade costs $3900) comprising more aggressive bumpers and side skirts, a platinum grey rear diffuser, chrome exhaust trims and S line badges.

A6 customers can opt for a Technik upgrade pack for $4095 that adds a top-view 360-degree camera system, full LED headlights with automatic high-beam, and quad-zone climate control.

Gadget fiends can also fit a digital TV receiver for $2300 on the A6 or $2650 on the A7, while a 15-speaker, 1200-watt Bang & Olufsen audio upgrade is a snip at $10,400.

Crash-test authority ANCAP has awarded the A6 range the maximum five-star rating.

Six-cylinder variants of the A6 and A7 ranges received hefty price cuts late last year – including $9000 lopped off the single-turbo V6 diesel A6 and $7000 off the equivalent A7, ensuring a suitably large premium of $11,300 (A6) and $12,850 (A7) for the BiTDI counterparts.

Australian A6 and A7 sales slumped in the first month of this year, with a combined 51 units sold compared with 90 in the same period of 2012.

Audi sales grew just 0.2 per cent last year to 14,535 units, while BMW and Mercedes-Benz were both up around five per cent.

Audi A6/A7 BiTDI pricing*

A6 3.0 TDI Biturbo (a)	$118,800
A7 3.0 TDI Biturbo (a)	$148,600

Plus on-road costs