Turbo six for BMW

BMW will depart from tradition and announce a forced-induction petrol six at the Geneva show.

The inline six-cylinder engine will feature twin turbochargers. While some markets received a blown six-cylinder 7 Series in the 80s, the new engine will be the first turbocharged petrol six-cylinder engine to feature in a series production BMW.

Based on the mag-alloy N52 3.0-litre 24-valve six (pictured), the new engine is not sequentially turbocharged. That is, each turbo serves three cylinders -- rather than differentially-sized turbos pumping into all six pots.

Output is placed at a relatively modest 225kW in road-going guise. This would indicate relatively low boost pressures and an emphasis on driveability rather than outright power. The naturally-aspirated version of the 3.0-litre engine boasts 195kW in 130i form and 190kW in both 330i and 530i instrallations.

The engine uses direct petrol injection also a first for a BMW inline six. The V12 powered BMW 760i/Li features direct petrol injection for its 6.0-litre engine.

The low-blow six is, however, expected to deliver enormous torque -- 400Nm across a wide rev range (from 1500-5800rpm). By way of comparison the N52 3.0-litre engine develops 300Nm at 2500rpm and the current M3 powerplant, 365Nm at 4900rpm.

BMW is being extremely tight-lipped regards what it will call the new engine and the models in which it will feature. The maker's twin-turbo diesel (also pictured) 3.0-litre is dubbed the 535d in its 5 Series guise.

Rumour has been rife that the petrol twin-turbo engine will first surface in a '335i' badged version of the new generation 3 Series coupe. The two-door variant of the new E90 series is due mid-2006.

Adding weight to the 335i rumour are the performance figures being bandied around for the new engine. According to BMW sources, the twin-turbo is just 0.5sec quicker than the 330i in the 0-100km/h sprint but a whopping 2.0sec faster from 80-120km/h in top gear.

No news either on whether the engine will be mated to auto or manual gearboxes. That said, it's CarPoint's understanding that BMW does not currently have a manual gearbox suited to the engine's prodigious torque output. We'd bet on auto-only to kick off, with (possibly) an SMG sequential manual option down the track.

While gazing into the crystal ball, is worth looking at the 335i's relationship to the long-rumoured V8-engined M3 replacement. Expected to pack 8/10ths of the M5's 370kW-plus V10, compared to the current 252kW six-cylinder M3, the new 300kW V8 M3 will create 'room' for BMW to increase the output of the twin-turbo engine and in the process counter Mercedes' push to give the C-Class sedan more muscles via new V8 engines.

To most of the world's auto consumers this power battle will mean little, but hey, talk of 250kW turbo sixes in tight rear-wheel drive midsized packages is a lot more fun than fuel-sipping ethanol-fuelled hybrids!