Federal emission standards have kept Mini from bringing the diesel-powered Mini Cooper D to the U.S. and higher standards have finally put any notion of the car coming to the U.S. to rest. However, Mini has the answer with next-generation gasoline engines that are reported to achieve just under 50 mpg U.S. on the highway.
The Mini Cooper D is powered a frugal 1.6-liter turbo-diesel four-cylinder that produces 110 horsepower and 177 pound-feet of torque -- figures that compare very favorably with the standard Mini Cooper’s 118 horsepower and 114 pound-feet of torque offered in the U.S (121 horsepower and 118 pound-feet of torque in 2011 models). What the Mini Cooper D does far better than the Mini Cooper however, is sip fuel. The Mini D gets 62 mpg (U.S.) versus the standard Mini Cooper’s 43 mpg (U.S.), both on the European combined cycle for direct comparison. The EPA rates the Mini Cooper at 32 mpg combined.
Mini does, however, plan to rectify this fuel economy situation for U.S. customers. The Mini Cooper D will remain an exile from the U.S. market, but Mini’s next-generation gasoline engines are reported to achieve fuel economy figures just under 50 mpg freeway, far exceeding the current Mini’s 37 mpg highway rating.
In order to achieve this impressive rating, Mini will downsize its engines and decrease cylinder count. The current engines in Mini’s lineup are a 1.6-liter four-cylinder in normally aspirated and turbocharged configurations. The next generation engines will have three cylinders, direct-injection, and turbochargers. Direct-injection makes its first appearance on 2011 model year engines.The standard next-gen engine is reported to have a displacement of 1.3-liters and the Cooper S engine is reported to be 1.5-liters. The smaller, 1.3-liter is the engine reported to achieve around 50 mpg freeway, no fuel economy figures are estimated for the larger Cooper S engine yet.
Despite the decreased size and cylinder count, Mini is not decreasing the power in either the Cooper or Cooper S. Both will retain their respective ratings of 118 horsepower and 172 horsepower. The use of direct-injection and highly efficient turbochargers along with the smaller displacement and decreased cylinder count ensures better fuel economy figures without sacrificing power.
A three-cylinder engine configuration leads to lower internal friction than the four-cylinders used now, reducing power loss from the internal resistance and operating temperatures, improving both power and fuel economy. Direct-injection enables the engines to run cooler, allowing for higher compression ratios and more complete combustion -- once again improving both power and fuel economy. The smaller displacement engines inherently burn less fuel and the highly-efficient turbochargers reduce back pressure to improve fuel economy and allow the smaller engines to produce as much power as the engines used today.
Source: Motoring File