Official: BMW 2.0-litr four-cylinder turbo engine for U.S. image

After 11 years of absence, BMW announced the return of a four-cylinder engine to the US BMW line-up.

This new four-cylinder engine uses the same twin-scroll turbo technology found in the larger N55 3.0-liter engine. With 240 horsepower and 260 lb-ft of torque, it offers more power and torque than BMW’s normally aspirated 3.0-liter inline six. It will arrive later in 2011.

The four-cylinder engine with its all-aluminum crankcase is lighter and more compact than a six-cylinder engine of equivalent power. The turbocharger is a twin-scroll system. The exhaust streams leaving the two pairs of cylinders are kept completely separate as they flow through the exhaust manifold and the turbocharger, taking a spiral path to the turbine wheel. This configuration results in very low exhaust back pressure at low engine rpm, and allows the energy of the exhaust gas pulses to be optimally managed and translated into powerful rotation of the turbine blades, without a delay in throttle response.

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For the moment, the automaker has not unveiled any fuel consumption details, or, on what cars they will use this unit. According to the latest rumors, Z4 sDrive30i will now use four-cylinder power, and we’re betting both the 1 and 3 Series, as well as X1.

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