BMW 5-series is in line for the company's new triturbo diesel engine

Details leaked from a dealer conference held in Holland this week suggest that BMW's upcoming 550dX will be the first recipient of the German carmaker's new high-tech triturbo 3.0-liter inline six-cylinder diesel engine.

The new engine, which also is destined for the new X5 xDrive50d and X6 xDrive50d models, is claimed to produce 376 hp and more than 516 lb-ft of torque--some 70 hp and more than 74 lb-ft more than the most powerful version of BMW's existing twin-turbocharged 3.0-liter inline six-cylinder diesel engine, as found in the X5 xDrive40d.

The radical new engine, which is rumored to use two traditional exhaust-blown turbochargers in combination with an electrically driven turbocharger to add low-end response, is planned to be offered exclusively with an eight-speed automatic gearbox and four-wheel drive.

The 550dX will slot into the BMW lineup above the 535d, although North American sales have not yet been confirmed. Nothing is official just yet, but Munich insiders hint at 0-to-62-mph acceleration in about five seconds and a top speed limited to 155 mph. And, combined-cycle fuel consumption is said to come close to matching the 535d's 38.3 mpg.

Along with the standard version of the 550dX, BMW also is planning a performance-oriented M550dX. While not an official M model, it will get various chassis and styling changes, according to highly placed BMW sources.

Original plans for a full-blown M5 diesel were ditched on the grounds that the 550dX's four-wheel-drive system would have dictated the ride height. "There are specific reasons why we didn't go with four-wheel drive, one of them being the four-wheel-drive system that requires the car to ride higher than existing M models," a source said.

Meanwhile, further information from the BMW dealer conference suggests that engineers are well advanced on a new M135i based on the recently introduced second-generation 1-series hatchback.

The new Audi RS3 rival, tentatively scheduled to go on sale in Europe in mid-2012, is said to run a powered-up version of the 135i's N55 engine. The twin-scroll turbocharged 3.0-liter inline six-cylinder is rumored to push out 315 hp and about 332 lb-ft of torque.

By Greg Kable