BMTS exhaust gas turbocharger in the BMW three-cylinder diesel engine

BMW has made the three-cylinder diesel engine fit for use in the sports-oriented premium segment. The manufacturer counts on the Bosch Mahle Turbo Systems (BMTS) exhaust gas turbocharger with variable turbine geometry. The turbocharger adds appealing acoustics, pronounced dynamics, and maximum efficiency to meet the high standards of the sporty brand.

The demands on modern turbocharging units intensify as the downsizing rate increases. To fulfill the requirements for efficiency and dynamics, the turbocharger plays a crucial role. Turbocharging is a basic technology for highly efficient downsizing engines. Specially designed for the BMW three-cylinder diesel engine, BMTS has thus developed a particularly performance-oriented exhaust turbocharger with variable turbine geometry (VTG). At the same time, the exhaust turbocharger is extremely efficient due to an outstanding chain efficiency of the turbine and compressor, and reduces fuel consumption. The optimized blade design of the VTG and a low-friction bearing lend the engine a spontaneous response behavior, especially in the low speed range, and thereby a broad torque plateau at a high level. Thanks to the electrical control of the guide vanes, a faster adjustment is possible with significantly lower hysteresis at the same time.

In the premium segment, in particular, the demands on acoustics are especially high, in addition to the desired dynamic behavior of the turbocharger. Therefore, the BMTS VTG turbocharger is equipped with particularly low-noise, weight-optimized actuating elements with plastic bushings in the coupling rod, a floating bush bearing with acoustic package, and a milled impeller for less pulsation noise.

At its St. Michael/Austria location, BMTS has set up state-of-the-art production facilities in order to implement the high technology standards in large-scale production while maintaining its commitment to quality. What BMW describes as “an outstanding improvement in the turbocharger assembly” is in fact the end-of-line test—i.e., at the end of the production line, manufacturing parameters and balancing values of each turbocharger are checked in a fully automated process to document highest quality and precision. The high quality of the finished BMTS turbocharger was established, for example, in so-called misuse tests: the BMTS component survived all test runs at BMW unscathed, which usually lead to the destruction of the impeller—and thus is already prepared for even greater demands in the future.

Together with BMW, BMTS has also developed a new packaging concept for the finished turbochargers. Instead of sealing the openings of the turbocharger, as done previously, the exhaust gas turbocharger is placed on a support and completely enclosed with a plastic casing to protect it against contamination. The extremely low tolerances in terms of the size and quantity of dirt particles can thus be more easily observed and even the handling is greatly improved.

With the three-cylinder diesel engine with 1.5-liter displacement, the BMW Group consistently rounds off the new engine platform that is characterized by a standard cylinder capacity of 500 ccm found in all BMW diesel and gasoline engines. This new engine is installed both lengthwise and transversely—in two power output levels with 70 and 85 kW—in different models.