CALL it an A4 hatch at your peril, because Audi will insist that you see the new A5 Sportback as an elongated A5 Coupe with a longer wheelbase, more doors and a tailgate.

Undercutting the latter by about $1500, the Sportback is now the entry level A5, available in $78,400 2.0TFSI quattro and $89,100 3.0 TDI quattro guise.

An S5 Sportback arrives later in 2010, while front-wheel-drive variations are also thought to be in the pipeline for Australia, but Audi won’t confirm this.

Believe the hype and the A5 Sportback trailblazes a new niche in the luxury market, with the next BMW 3 Series expected to field the similarly configured GT against it.

But Audi’s claim conveniently ignores every current era Saab 9-3 and 900, the 1976 Rover SDI and its 1988 800 Fastback successor, and even the Renault 25 (1984) and Safrane (1992).

Furthermore the Ingolstadt spin-doctors cannot deny the B8-series A4 connection underneath the A5 Sportback since both share Audi’s MLB (Modulare Längsbaukasten) componentry also serving the A5 Coupe and Cabriolet, Q5 SUV, 2011 A8, 2011 A7 Sportback, and 2012 A6. And more are expected.

MLB, by the way, refers to the company’s latest longitudinally mounted drivetrain layout that sees a more centralised placement of the engine, gearbox and steering systems over the front axle for improved dynamics due to more balanced weight distribution.

Stylistically the Sportback looks more like a slammed A4 sedan than a stretched A5 Coupe despite both sharing the latter’s nose treatment, with four frameless doors (remember those Subaru?) and a sleek six-window profile boasting a small up-kink that is meant to evoke the 1969 Audi 100 Coupe S of 1969.

But its 0.29Cd drag co efficiency is just 0.1Cd better than the 1982 Audi 100.

The cabin is designed for four people and comes with only four seatbelts as a result. Interior space is comparable to the A4, Audi says, although rear space is hampered by the sloping rear.

The hatch capable of swallowing 480 litres of luggage, or 980 litres if the split-fold rear seats are dropped.

Proportionally speaking, there are key dimensional changes between the B8 vehicles.

Taking length (4711mm), width (1854mm), height (1391mm), and wheelbase (2810mm) into consideration, the differences between the A5 Sportback and its A5 Coupe and A4 sedan siblings are 86mm and 8mm, 0mm and –¬2mm, 19mm and –36mm, and 59mm and 2mm respectively. The former is also slightly longer than the others in the front track (1590mm) while the rear track (1575mm) is just 2mm shy of the Coupe’s.

As with all A5s, the Sportback version leverages a five-link front and trapezoidal-link rear suspension system, along with a hydraulically powered rack and pinion steering system and dual-circuit brakes with ventilated discs up front and solid discs at the rear.

Besides the usual ABS and ESC stability and traction controls, Audi’s $3500 Drive Select variable electronic damper system is an option, while the 3.0 TDI is also available with the company’s Sport Differential that oscillates torque between the left and right rear wheels according to traction requirements.

The 2.0TFSI quattro employs the same Euro 5 emissions-compliant turbocharged 1984cc twin-cam 16-valve direct petrol injection unit found in the other B8 cars, featuring variable valve timing, chain drive for the camshafts, a trick intercooler design and a cornucopia of friction minimisation measures for big efficiency outcomes.

Power is rated at 155kW between 4300 and 6000rpm and torque tops out at 350Nm between just 1500 and 4200rpm.

From standstill, the 1615kg 2.0 TFSI quattro (weight about 10kg more than its Coupe equivalent but almost 84kg more than the matching A4 sedan) can sprint to 100km/h in 6.6 seconds, reach 241km/h, average 7.5 litres of 95 RON premium unleaded petrol per 100km and emit 174 grams of carbon dioxide per kilometre.

In contrast, the 1720kg 3.0 TDI quattro – with its 2967cc 3.0-litre variable geometry turbocharged and common rail Piezo injection system V6 delivering 176kW from 4000 to 4400rpm and 500Nm from 1500 to 3000rpm – is 0.5s faster to 100km/h, nudges 250km/h, and yet returns 6.6L/100km (the 23rd Audi to do so thus far for a federal government luxury car tax waiver), and scores an equal 174g/km of CO2 rating.

Benefitting the latter result, both models include Audi’s energy recuperation system recovered during braking and deceleration, and stored temporarily in the battery.

The S5 Sportback, by the way, will be powered by the supercharged 2995cc 3.0-litre TFSI V6 developing around 245kW and 440Nm.

Drive is sent to all four wheels via Audi’s trademark Torsen differential quattro all-wheel drive system working in conjunction with Audi’s new seven-speed S-tronic transmission once known as DSG.

In normal conditions, the A5 Sportback’s rear axle sends 60 per cent of available torque and the front end drives 40 per cent, for a greater rear-wheel drive ‘feel’ than in pre-B8 A4 and derivatives (B7 RS4 excepted).

However, in certain conditions, up to 65 per cent of drive is delivered to the nose end if necessary, while the rear wheels can receive up to 85 per cent of the available torque.

Even the base A5 Sportback includes front side and curtain airbags, leather upholstery, High Intensity Discharge Xenon ‘Plus’ headlights with LED driving lights, three-zone climate control air-conditioning, keyless-entry and keyless start, electrically adjustable front seats, mobile phone preparation with Bluetooth connectivity, a multi-functions steering wheel, a 10-speaker sound system, rear parking sensors and 17-inch alloy wheels shod with 245/45 R17 tyres.

Going for the 3.0 TDI quattro gives you 18-inch alloys wearing 245/40 R18 tyres, as well as front parking sensors and some trim upgrades.

Key options include MMI Navigation ($4550), adaptive radar cruise control ($2945), a blind-spot warning system ($1430) and a large glass sunroof ($2860). An ‘S-Line’ body kit adds another $6200 (2.0TFSI quattro) and $4500 (3.0 TDI quattro) to proceedings.

So who’s going to buy the 1000 or so cars that Audi has forecast?

The firm refuses to concede that there are rivals out there at the moment, dismissing the Volkswagen Passat CC and Mercedes-Benz CLS because of their inherent three-box booted designs.

Audi is counting on the 2.0 TFSI quattro to account for around 70 per cent of all A5 Sportback volume, with the 3.0 TDI quattro taking up the remaining 30 per cent.

It is also expected to be the most popular A5 variant, charged with collecting about 46 per cent of volume compared to the Coupe’s 35 per cent and the Cabriolet’s 19 per cent totals.

Audi concedes there may be some sales cannibalisation between the A4 and A5 Sportback, but expects the latter to become a volume seller with an identity in its own right.

“It seems that once again Audi has managed to successfully combine conflicting traits – blending emotional design with a car that is functional in terms of space, even offering a very large rear tailgate for ease of access. It looks beautiful. It drives very well. It is a great car for a family, for everyday use and I believe it will sell very well Down Under,” outgoing managing director Joerg Hofmann said.

“It will be our volume-selling model in the A5 segment and will make a significant contribution to our sixth record year of sales in 2010.”