Welcome to the turbo class: Turbochargers in BMW engines optimise torque development, improve performance and reduce consumption.
An engine’s performance and efficiency depend on the amount of oxygen in the combustion chambers. More oxygen available means more fuel released and improved performance. A turbocharger uses the otherwise unexploited energy from the exhaust gases to provide more oxygen for combustion; this is done by means of a compressor powered by a turbine fan, which compresses the air taken in. This increases the pressure in the engine’s air intake manifold and thus fills the cylinders. The result is improved performance and more torque over a broad plateau. Modern turbo technology simultaneous reduces consumption and emissions.
In addition to optimising their response and dynamics as well as improving their performance and consumption, BMW uses the principle of double charging for its most powerful turbo engines in each class. Depending on the technology involved, two separate turbochargers from one exhaust pipe or one turbocharger from two separate exhaust pipes are used. In particularly powerful models like the BMW X5, these Twin Scroll turbos even provide the engine with air.
Use of two turbochargers:
Two different technologies come into play when two turbochargers are used. The bi-turbo technology uses two equally large turbochargers set up parallel to each other. Each turbo supplies half of the cylinders with pre-compressed air. Combined with the high-precision injection, this technology enables particularly effortless power output and very low consumption.
In contrast, the Variable Twin Turbo technology used in BMW diesel engines uses a large and a small turbocharger connected in series. At low speeds air enters the inactive large turbocharger and is compressed in the small one. At mid-range speeds the air in the large turbocharger is pre-compressed before being highly compressed in the small turbocharger. At high speeds only the large turbocharger is in use. This two-tiered charging enables extremely low consumption values, in relation to performance, and easy to control response from the powerful BMW diesel engines.
Use of a turbocharger:
BMW Twin Scroll technology consists of a sole turbocharger driven through two exhaust pipes. As it does with two smaller turbochargers this double charging causes a quicker build-up of pressure and thus more direct engine response. However the Twin Scroll turbo takes up less space and saves weight. The result: better dynamics, improved performance, less consumption.
The combination of tailor-made charging technology with the BMW High Precision Injection and "VALVETRONIC" (Otto engines) or the 3rd generation (diesel) common rail direct ignition is called BMW TwinPower Turbo technology. It enables a unique combination of efficiency and dynamics.