TUCKED behind a pillar at BMW¡¯s Detroit exhibit are the guts of a new gasoline direct-injection twin-turbo V-8 that might have deserved a starring spot in the carmaker¡¯s display.

That¡¯s because the 400-horsepower 4.4-liter engine that powers the new X6 crossover turns engine architecture on its head. It places the intake manifolds low on the outside faces of the cylinder heads and nestles the turbochargers, exhaust manifolds, catalysts and control equipment up high in the 90-degree V of the engine.

 

Turbochargers use an exhaust-driven turbine to compress and pump intake air into the cylinders; this improves the power and efficiency of most engines. Traditional engines carry the intake up high and the exhaust manifolds down low, with turbochargers mounted near the engine exhaust outlets.

 

Wieland Bruch, a BMW spokesman, said the new engine had a closer coupling of the turbos that reduced pressure losses on both the intake and exhaust sides and offered larger cross sections over a shorter run for easier air flow than conventional side turbo placement.

 

He said turbocharger durability was crucial to mastering the high temperatures of the system. The all-aluminum engine is dependent on turbochargers made with aerospace materials capable of withstanding the high temperatures of gasoline exhaust, he said, without the need to cool emissions by using extra fuel.