BMW 7 Series Returns to Its Roots With a 6-Cylinder BMW is finding more places to put its magnificent twin-turbocharged in-line-6 engine. The latest host is the 7 Series luxury sedan. The turbo straight-6 first appeared in the BMW 335i coupe. When the engine later appeared in the 135i, the pairing almost seemed like overkill - 300 horsepower in a small lightweight sports car? It was a bold move, but also a fantastic one to reaffirm BMW as a performance-minded company. Putting the turbo straight-6 in the 740i and 740Li could be an even bolder decision. Owners of large luxury sedans are used to V-8s and even V-12s. Although BMW has upped the power output to 315 horsepower in this latest iteration, the 7 Series could appear lacking to German luxury car customers used to hearing the deep grunt of big V-8s. Nevertheless, it is the sign of the times. Many automakers are preferring fewer cylinders and phasing out V-8 engines. Ford is using its turbocharged EcoBoost 4- and 6-cylinder engines for traditionally V-6 and V-8 applications. And the recently released 2010 Toyota 4Runner will not have a V-8 option. BMW adds a historical slant to its decision. In a news release, the company highlights the original 7 Series, which came with an in-line-6 when it was launched in 1977. In the United States, the 1978 733i came with a 3.2-liter in-line-6 (later replaced with an updated version making 218 horsepower). But it's been more than a decade since the 7 Series had a 6-cylinder engine option in the United States. The current-generation 7 Series was launched last year with a twin-turbocharged V-8 in the 750i. The 760Li is also available with a twin-turbocharged V-12. Even the hybrid version of the 7 Series, the ActiveHybrid 7, which is due in the second quarter of next year, is equipped with a twin-turbo V-8. BMW says that the smaller engine provides the "power of a larger engine" with better fuel efficiency and lower emissions. The 740i and 740Li will be equipped with a 6-speed automatic transmission and go on sale in the spring. No word on price yet.