SPY PICS: Audi's fifth A4 shapes up

No car has been more important to Audi’s inexorable march than the A4 and it’s almost time for a new one.

Almost. Unlike just about every other new car you’ll read about in the next couple of weeks, the fifth-generation 'B9' A4 won’t be at the Geneva motor show early next month.

Instead, its combination of evolution and revolution won't be shown until a few weeks before the Frankfurt motor show in September.

Its design is said by insiders to pay heavy homage to the outgoing, and very successful, fourth-generation A4. However, Audi hopes a new interpretation of the single-frame grille, standard LED headlights and a very low nose will mark it as something new and different.

Led at one end by an Ultra model emitting fewer than 100g/km of CO2 and initially topped by a 2.0-litre TFSI, the A4 range will eventually spread to an S4 and an even more powerful RS 4, though Audi refuses to hint at whether this will use a version of the RS6’s twin-turbo V8.

It will also use 1.4-, 1.8- and 3.0-litre petrol engines and its turbo-diesel options will spread from 1.6- and 2.0-litre fours to a single 3.0-litre V6. With the A4 sitting atop Audi’s lighter new MLB2 architecture, expect all the A4's engines to sit longitudinally in the chassis, even when they drive the front wheels.

There will also be a plug-in hybrid e-tron version of the next A4, complete with around 50km of range on battery power alone.

While the e-tron will combine the electric motors with a 1.4-litre turbo-petrol engine, Audi is also said to be working on a diesel-electric hybrid, though it may not reach the A4 until its late-cycle facelift in around 2020 – just in time for the new, tougher, 95g/km CO2 limit in Europe.

The continuously variable transmission (CVT or, in Audi-speak, Multitronic) has had its day in the A4, replaced by either six-speed manual or nine-speed automatic transmissions. All-wheel drive will, as you’d expect, be optional though all A4 models will come with front-wheel drive as standard.

Expect Audi to make its first A4 splash with the sedan, though the Avant has been designed alongside it and only market rollout reasons will stop it being immediately sold alongside the three-box version. The wagon will again form the basis of an A4 Allroad crossover.

The design of the A4 will be slightly cleaner than the current car's, though insiders insist it has discovered some new engineering tricks to give the car a very low bonnet line that still meets all the world’s pedestrian impact criteria.

Audi is said to have designed a special hinge that allows it to use a clamshell bonnet, the lower edge of which will form a key part of the car’s 'tornado' line, which is hidden under the camouflage of this prototype spied in testing.

It will be a wider car than the existing model and will ride on a slightly longer wheelbase, even if it will be roughly the same overall length and height.

It is also said by insiders to take lessons from the TT’s radically minimalist interior, though it will use a touch-screen multimedia screen in the middle of the dash as a nod to its reater passenger focus, rather than the sports car’s intensively driver-centric instrument cluster.

The A5, due in 2016, will share the A4’s MLB2 architecture across its five-door Sportback and two-door coupe and convertible body styles.