|The water-cooled aluminum turbine housing. Click to enlarge.|
Continental’s powertrain developers have launched series production of the first car turbocharger with an aluminum turbine housing. Integration of the unit in the three-cylinder, 1.5L 100 kW gasoline engine for the MINI Hatch (earlier post) has been ongoing since spring 2014.
Water-cooling enables the use of the lightweight material and thus enables a significant weight reduction by nearly 30% while simultaneously providing cost and system benefits.
It’s not just the aluminum that makes the turbocharger special; it was also developed from being a typical add-on component to an integral part of the engine. In order to meet the requirements placed on the unit and its integration in the cylinder head, we worked closely with the BMW Group starting from the simulation phase—an indication of trust that we greatly appreciate.—Udo Schwerdel, Head of the Turbocharger Product Line, Engine Systems, Powertrain Division
Full-load operation can be enough to make common turbocharger constructions with a steel housing glow red with heat; in Continental’s new unit, a double-walled aluminum housing surrounds the hottest area with a cooling water jacket. The coolant flowing through this jacket ensures that the external housing surface does not get hotter than 120 °C (248 °F) and the internal temperature does not exceed 350°C (662 °F), which as Udo Schwerdel explains, has two benefits:
First, much less effort is required to protect neighboring components from the heat.
Second, cooling of the exhaust flow reduces the thermal load on the catalytic converter, meaning it hardly ages at all.
At the same time, the dynamic response of the electric actuator at the wastegate ensures that the catalytic converter heats up quickly.
In keeping with the modular principle specified by BMW, the turbocharger is tightly integrated in the engine (it is a fixed component of the exhaust manifold), but Continental turbochargers with a steel housing can also be attached to the same base engine using the interface on the cylinder head.
The car manufacturer is using this option for high-performance engines as well as vehicles for export to hot countries. The bearing housing is cooled from inside the turbocharger for steel variants, while cooling from outside is sufficient for aluminum turbochargers.
In the MINI, 1.2 kg (2.6 lbs) of weight is saved per aluminum turbocharger. Since reduced weight also means reduced fuel consumption, the lightweight material supports the fuel consumption and emission targets of the automotive industry. Despite the additional expenditure for the water cooling, aluminum turbochargers are more affordable for automotive manufacturers.
High-temperature-resistant materials such as nickel-base alloys drive up prices for turbochargers with steel housings, whereas our aluminum alloy is a cost-effective material.—Udo Schwerdel
The first Continental turbocharger went into series production in a highly efficient, multi-award-winning 1.0l engine in 2011.