First drive: Audi's Q7 V8 turbo-diesel delights

AUDI is about to unleash a mighty 4.2-litre V8 common-rail turbo-diesel version of its Q7 full-size SUV that produces 760Nm of torque – a whopping 110Nm more than the same engine in the A8 saloon.

Audi claims it is the highest torque figure in the world for an SUV, surpassing the 750Nm produced by the 5.0-litre V10 diesel found in parent company Volkswagen's top-shelf Touareg.

It also claims class-leading performance – at least until the projected 6.0-litre V12 Q7 arrives with an extraordinary 1000Nm on tap.

The 4.2 TDI was launched in Germany this week, but will not be released in Australia until October.

It will come only with a tiptronic sequential-shift automatic transmission and is expected to be priced at $123,900 - $5000 more than the similarly-specified petrol-engined Q7 4.2 FSI.

The seven-seat bahnstormer will accelerate from zero to 100km/h in just 6.4 seconds – a full second faster than the 257kW/440Nm 4.2-litre V8 petrol Q7 – yet it returns an impressive 11.1 litres per 100km on the combined fuel economy cycle (compared with 13.6L/100km for the petrol V8).

Audi’s Q7 technical development project manager, Dietrich Engelhart, told GoAuto that the Aisin six-speed transmission was the secret to untapping the potential of the V8 turbo-diesel in the Q7.

The big Japanese-built tiptronic transmission, which was introduced from the launch of the Q7 last year, was developed specifically with the turbo-diesel’s 760Nm of torque in mind.

Mr Engelhart explained that the chain-drive 4.2-litre engine – which should probably be called a 4.1-litre because the actual capacity is 4134cc – was capable of producing 760Nm from the outset, but it had to be reigned in for the A8 because the saloon uses a different transmission.

Although the maximum torque is developed over a relatively narrow band by modern standards (1800-2500rpm compared with the A8’s 650Nm from 1600-3500rpm), it begins tailing off just as the power reaches towards its maximum of 240kW (the same as the A8) at 3750rpm.

As well as providing effortless performance, the twin-turbo intercooled diesel propels the big SUV to a top speed of 236km/h.

Drive is through all four wheels, with a 42:58 torque split favouring the rear wheels under normal driving conditions - instead of Audi's usual (until the A5, at least) passenger car torque dsitribution of 50:50). Like lesser Q7s, up to 65 per cent of torque can be directed forwards, and 85 per cent rearwards, if conditions require it.

Innovative technologies featured in the Q7 4.2 TDI include a lane-assist system that alerts the driver through vibrations in the steering wheel if the vehicle begins to veer out of its lane without the indicator being activated.

This lane assist system will be a $1200 option in Australia and will be introduced to the rest of the Q7 range from next month.

The 4.2 TDI features the same electronically-controlled adaptive air suspension system as the 4.2 FSI, with three settings – sporty, comfortable or automatic. In off-road mode, the suspension rises to provide 205mm of ground clearance, while the rear can be lowered by 71mm to aid loading.

Standard equipment includes eight airbags, traction/stability control, aluminium roof rails, rear parking camera, heated mirrors with auto-dimming function, electric tailgate, automatic Xenon plus headlights, driver information system with seven-inch screen, leather upholstery, 11-speaker sound system, electric seats with lumbar support and a sports steering wheel with gearshift paddles.

Audi Australia expects the 4.2 TDI to account for up to 10 per cent of Q7 sales, which means 150-plus units a year.

Drive impressions:

ACCELERATE onto a German autobahn and you quickly begin to understand why European car-makers are so focussed on performance and dynamic abilities in their vehicles.

It is not only important to get up to speed quickly to avoid getting mown down by the pack, but you need to explore the upper reaches of the car’s speed capabilities to enjoy the benefits of the fast lane – and then you start thinking about braking and stability in case someone wanders into your path (which is thankfully rare in switched-on Europe).

Suddenly, having a 4.2-litre turbo-diesel V8 with 760Nm stuffed into an SUV makes all the sense in the world. Had we been paying for juice, it would have made even more sense.

Audi has created arguably the definitive Q7 in the form of the 4.2 TDI.

Not only is it quick and relatively economical, but the noise from the V8 is awesome. If you didn’t know it was a diesel, you would never pick it from the sound of this fabulous engine.

While the standing-start performance is impressive enough for such a big machine, it is really midrange pick-up where the TDI shines, providing tremendous response and overtaking ability.

With every gear there is a surge forward until you are suddenly doing more than 200km/h – and still accelerating.

From low speeds there is a little hesitation before the transmission decides you are really serious, but then it’s all business.

The shift quality is superb, providing effortless and seamless progress, but we detected a bit of wind whistle between 90 and 140km/h that could be a little uncomfortable when cruising Australian freeways.

Handling is pretty good for a vehicle of this size, but of course when push comes to shove, it will push.

Comfort levels are excellent, the variable-speed steering predictably errs on the light side and there should be no trouble with the brakes, with six-pot calipers fitted to the big front discs.

Overall, the Audi Q7 4.2 TDI is a mighty performer. It might be better suited to the autobahns, but will surely delight enthusiasts requiring the attributes of an SUV in motoring-unfriendly Australia all the same.

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