From £30,340
The new flagship Audi A6 oil-burner has speed to burn, but it lacks the poise and engagement of a sporting great

What is it?

An Audi A6 that’s been eight years coming. That’s how long Audi brand devotees have been waiting for Ingolstadt to produce a reply to one of the most convincing modern sports saloons of the last decade: the defining hot diesel exec, BMW’s 535d. Which seems prudent in the extreme considering the ascendant car-maker’s phenomenal expansion in other segments, its continued investment and improvement in ‘TDi’ diesel technology across the board, and the obvious marketing opportunities delivered by its five diesel-powered wins at Le Mans.

But finally, that reply has arrived on British shores: it’s the A6 BiTDi. Just like BMW did, Audi has turned to twin-turbocharging to produce a sizeable slug of extra performance from its 3.0-litre six-cylinder commonrail diesel engine. It will be offering it in the A6 saloon, A6 Avant, new A6 Allroad and A7 Sportback this year.

The engine’s basic architecture is the same as it is with the two slighter-tune V6 TDi engines in the A6 range. The 2967cc unit is just 44cm long, weighs less than 200kg, uses a cast iron crankcase and an aluminium alloy head, and has an intelligent dual circuit cooling system which bypasses the crankcase for faster warm-up and greater efficiency on part-load. Its four camshafts are driven by two timing chains, which reduces both friction and weight compared to a four-chain drive system.

Sequential turbochargers have been adopted for this high-performance application; a small one (with variable geometry vanes) for increased low-rpm boost and a big one for greater power above 3500rpm, joined by a vacuum valve. The extra pressure put on the engine is handled via modified head cooling, revised intake cam timing and lift and reinforced pistons.

Peak power, at 309bhp between 3900- and 4500rpm, matches that of the BMW 535d exactly, while peak torque (479lb ft at 1450-2800rpm) exceeds that of the BMW twin-turbo. Which is why the performance claims are so serious: 5.1sec to 62mph for the regular A6 saloon. And, as is so appealing with fast diesels, economy is promised to be excellent too, at 44.1mpg.

There is only one transmission on offer with the A6’s new flagship diesel engine, and it’s an eight-speed torque converter automatic partnered with Quattro four-wheel drive. Otherwise, the BiTDi is marketed less like a full-blooded performance model and more like any other engine variant in the range.


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You can get one in SE or S-Line trim, and with or without Audi’s Drive Select adaptive dampers, variable ratio sport steering and a Sport rear differential. Our test car was a relatively humble ‘SE’ spec example with none of Ingolstadt’s more trick chassis and driveline gadgets. Oddly, it didn’t even have a ‘BiTDi’ badge to distinguish it.

What’s it like?

Next to a 535d or an XF 3.0D S, the A6 has a noticeable shortage of dynamic poise and sparkle – which we’ll come to address. The BiTDi powertrain’s throttle responsive could be improved, too. When you initially flex the accelerator at everyday cruising pace, it takes a split second for that eight-speed gearbox to kickdown, and another for the turbochargers to come on song. You can summon up too much mid-range torque at times, in a bid to mitigate the delay.

But once the engine’s woken up and hauling, its outright force is formidable. It burns through transmission ratios with disdainful urgency, spinning tunefully between 3000 and 4500rpm, and hurling the big A6 forward with the kind of pace that you could only find the margins of on derestricted German autobahn, above 100mph.

But what about in the outside lane of the M6 – or anywhere else in the UK, for that matter? The BMW 535d has long been revered by Autocar because, hand-in-hand with such fierce speed, it offers the taut, engaging handling of a proper sporting option. The A6 is a different sort of prospect. More comfortable and refined than the BMW, it seems much more geared towards the fleet market than the real-world thrill-seeker. It’s a high-performance business tool, rather than a performance tool well suited to business during the working week – that’s the bottom line.

And the difference is plain. While the A6 BiTDi would soothe away hundreds of miles of motorway in a near-effortless calm, it’s easily stretched through a tightening bend. The car’s steering wheel is large, and its rack slow just off-centre, making the front-end quite tricky to guide on a demanding road. Body roll is no better contained than in a fairly run-of-the-mill diesel family car. And while grip is actually quite equitably split between front and rear axles off the throttle, there’s more power-understeer than a keen driver would like during hard driving; little in the way of natural sporting poise to be enjoyed.

Should I buy one?

Maybe. As we discovered on the car’s launch last year, the A6’s ride and handling is extremely sensitive to optional specification. Spend close to £60k on a fully-loaded BiTDi S-Line, with adaptive damping, sport steering and a sport rear differential, and you could find it a greatly altered machine; a much closer match for a BMW 535d M Sport, even. Such is the richness of Audi’s options list at the moment. Or the paucity of the BiTDi’s standard specification, you could argue.

But this experience, as well as previous test drives, suggests that even a perfectly configured A6 BiTDi still couldn’t quite eclipse the BMW for overall dynamic appeal. In standard trim - though comfortable, usable, beautifully appointed, and ready with 479lb ft of pulling power – the Audi is a much more ordinary saloon than we were hoping for. It’s certainly no diesel S6 – which may be what many have been hoping for all along.

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Audi A6 3.0 BiTDi Quattro SE

Price: £43,810; 0-62mph: 5.1sec; Top speed: 155mph (limited); Economy: 44.1mpg; CO2: 169g/km; Kerbweight: 1790kg; Engine type, cc: V6, 2967cc, twin turbodiesel; Installation: Front, longitundinal, four-wheel drive; Power: 309bhp at 3900-4500rpm; Torque: 479lb ft at 1450-2800rpm; Gearbox: 8-spd automatic

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11 April 2012

What an ugly steering wheel!?! - Yuk! No wonder there is a nicer one on the 'options' list. "Spend close to £60k on a fully-loaded BiTDi S-Line, with adaptive damping, sport steering and a sport rear differential, and you could find it a greatly altered machine" How annoying that you now have to spend extra just to make the car handle properly. Id not hold your breath on the S-Line being much better to drive. Just more of the same but with a ride capable of removing your fillings.

11 April 2012

That's expensive.


12 April 2012

[quote Fidji]That's expensive.[/quote]

You're being generous. I'd say rip off.

BMW are as bad with the latest 5 though. In order to make the cars behave like their image suggests you have to spend a small fortune.

I wonder if it will be in Audi's plans to make a 550xd rival though?

EDIT: Yucky steering wheel. Strange that Audi make something that is so ugly.

BTW anyone knoe if the 8 speed auto is from ZF ?

12 April 2012

Maybe in another 8 years VW Group will reply to the tri-turbo 50d engine ? !

Much better badging than the BMW though-it always should been 530D Biturbo, 530D Triturbo or 730D Biturbo, none of this stupid 35d, 40d or 50d nonsense.

12 April 2012

it`s expensive?

so what, buy a MG6, it`s cheap!

oh dear! no diesels... and not this segment.

wait! try Lexus!

oops, no diesels either... damm, THAT is expensive!


12 April 2012

Yeah agree with comments a balanced sport saloon no longer comes as standard equipment from BM or Audi. I am curious to see what the forthcoming XF 4wd will accelerate 0-60 in. Problem with getting good figures on all these types of cars is traction so 4 wd addresses this.

12 April 2012

[quote Quattro369]What an ugly steering wheel!?! [/quote]

I wondered what you were on about so clicked on the 'more pics' to check. Blimey. Looks like somebody's bought an Audi branded bum-bag and fixed it to the steering wheel boss...

Still, if you're after a rapid diesel 4wd saloon there's not much else. (***cough*** Insignia ***cough***)

12 April 2012

[quote speckyclay]Still, if you're after a rapid diesel 4wd saloon there's not much else[/quote]

How about the M550d xDrive?

12 April 2012

I can see what you guys mean about the steering wheel!

12 April 2012

[quote Fidji]How about the M550d xDrive?[/quote]

As far as I am aware, that's not available in RHD...


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