Best-selling BMW 3 Series and Audi A4 do battle

It's one of the longest standing fights in the automotive ring - the battle for compact executive honours has often fallen to one of two motors: the BMW 3 Series or Audi A4. Both models represent best-sellers in their respective makers' range and can trace their history back more than 30 years. So with the release of an all-new BMW and revised A4, it looks like this is one fight that just got a whole lot tougher. Code-named F30, the new 3 Series promises to be better than the model that came before, in every single area. And considering that the current generation isn't exactly struggling to shine against newer competition, that's a big claim. Not only is there a new look, inside and out, and a line-up of new engine and chassis options, but there's also even a range of trim levels (called lines) that promise to make the new 3 more individual than before. But despite all of these newsworthy changes, Audi is aiming to land a sucker punch with its recently revised A4. The changes aren't nearly as extensive, but a raft of visual and mechanical updates makes the saloon an even stronger competitor. Catch sight of the 3 Series and it's clear that it's all change for the exterior design. Sure the inspiration (5 and 7 Series) is there for all to see, and it's obvious where this car slots into the line-up, but the front end, in particular, demonstrates a powerful new direction. The double kidney grilles are intersected by the headlights, and sit proud of the bodywork, and though most models share similar bumper and air dam layouts, different treatment to the plastic and bright work areas on each "line" shows a subtly different face. There's not nearly so much going on with the Audi but, like the best fighters, it's emerged through the three years since its launch with a comparatively fresh face. It still looks classy and understated, but now uses the same grille and headlight treatment found on the newest A6. One area where the new 3 Series really has to make its mark is with cabin space - too often the old model fell short against its competition. And with a 50mm increase in wheelbase, most of which translates into extra rear legroom, there's almost nothing to separate the pair in terms of room or comfort across the rear bench. There's little between them up front as well, and both demonstrate just how to construct a quality cabin, albeit in subtly different ways. Like the metalwork, the Audi hasn't changed much, which means a sober but driver-focused environment with clear instruments, a high transmission tunnel and high-tech feel to the equipment. On the other hand, it's clear the 3 Series has taken its direction from the latest 1 and 6 Series, resulting in a busier but still high-quality layout. It's not the way these cars look, or even feel when sat inside them, that really matters though; it's what happens when you turn the key that counts. And this is where the big news is in the BMW - the latest 3 Series features some of the brand's latest engine technology. The six-cylinder 335i remains, albeit with some minor tweaks for improved economy and efficiency, but it's the turbocharged 2.0L four-cylinder engines that make the biggest impact - especially the 328i. The most powerful of a pair, the 245hp unit, utilises TwinPower turbo technology (a variable vane charger) to offer 350Nm at only 1,250rpm. Along with the Precision Direct Injection, Double-Vanos variable camshaft timing and VALVETRONIC valve timing it makes for an incredibly flexible unit. Deploy all of that power from a standstill and the saloon will sprint from 0 to 100kph in only 6.1 seconds. Sure it doesn't sound as melodious as its bigger brother, missing that straight-six snarl at the top of its rev range, but a number of innovations have been applied to ensure it remains refined. A dual-mass flywheel and a pair of balancer shafts fitted at different heights result in a smooth and almost vibration-free lump and the 328i spins freely and fiercely all the way to the red line.