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BMW X6 to Get Single-Turbo N55 Inline-6, 8-Speed Transmission [2011]


BMW is really testing our memory and powertrain-matching skills with its 2011 lineup. One of our favorite current engines is the N54 twin-turbo 3.0-liter inline-six, which produces 300 hp and 300 lb-ft of torque in nearly every model in which it’s installed. But, as you probably know, it is being gradually replaced by an evolution of that mill, the N55 single-turbo inline-six, which still displaces 3.0 liters and produces identical horsepower and torque figures. The new engine is showing up first in the 535i Gran Turismo, and also will appear in the 2011 135i, 335i, and 535i. Now there are plans to shuffle it into the 2011 X6 xDrive35i, too.


Two More Speeds and New Tech for the X6



Beyond the new engine for the base model, both the 2011 X6 xDrive35i and xDrive50i models will receive a new, ZF-sourced eight-speed automatic transmission, as well as an energy regeneration system that uses a special alternator that charges only when the engine isn’t under load. The changes are being touted as improving efficiency—a hilarious statement given the X6’s inefficient packaging and thirst for fuel. In any event, expect the X6’s engines and transmissions to be available in the refreshed 2011 X5, which begins production in April.


The new transmission is said to increase performance in both X6 models; the xDrive35i is claimed to be quicker to 60 mph by 0.2 second, whereas the twin-turbo V-8 xDrive50i knocks 0.1 second off its time. We’ve clocked the 35i as sprinting to 60 mph in 5.9 seconds and the 50i in five flat, so we’re eager to see if BMW’s claims hold true. The company says the changes improve efficiency by seven percent, but didn’t quote specific fuel-economy numbers; the 2010 X6 xDrive35i and xDrive50i are rated at 15/21 mpg and 13/18 mpg, respectively. Other subtle changes for the 2011 X6 include the addition of lane-departure warning ($950) and active cruise control ($2400) as stand-alone options and the bundling of side-view cameras into the Technology package. The base prices will remain unchanged, at $57,375 for the 35i and $68,075 for the 50i.
A Quick Primer on the New Engine
The new N55 combines direct-injection and Valvetronic variable valve timing with a single twin-scroll turbocharger, which BMW says will spool up faster than the N54’s twin-turbo setup, eliminating nearly all lag. It’s said to be both more efficient and less emissions-spewing than the N54. As we said, reported output stands pat, with 300 hp arriving at 5800 rpm and 300 lb-ft of torque available from 1200 to 5000 rpm, the latter coming 200 rpm lower than before. But many—including us—believe that the N54’s power was underreported by BMW, so we’re not entirely convinced that we’ll see improved performance numbers among its many applications.
The N54 twin-turbo engine is not going away. Instead, BMW is increasing its output to 315–335 hp and relegating it to higher-performance vehicles; these include the 2011 335is, Z4 sDrive35is, and the 740i/Li. Why not just offer the single-turbo engine across the board with different power ratings? BMW says it had more experience tuning the old N54, and that meant it was easier to tailor it to increased-horsepower applications. Given that, we wouldn’t be surprised if it ultimately does disappear once BMW’s engineers get more familiar with the new N55’s limits.