The consequences of global warming have forced the governments of developed economies to impose strict regulations on the emission of so called ‘green house gases’. Carbon dioxide, a by-product of fossil fuel combustion, is a major contributor to global warming. The focus of government treaties, in the face of continued globalization and third world development, has been to stabilize contributions of carbon dioxide to the atmosphere.
Vehicle manufacturers and suppliers have tackled legislation and consumer pressures in a variety of ways. One of the most effective ways to reduce fuel consumption of passenger vehicles, consequently reducing their CO2 emissions, is so-called “engine downsizing”. This involves the improvement of the torque of a smaller displacement engine with respect to (w.r.t.) a given engine installed in a vehicle, and the use of longer gear ratios in the transmission.
In this paper a downsized demonstrator C-Segment vehicle is presented, equipped with a 1.4 dm3, inline, 4 cylinder, 16v gasoline engine, which gives a significant reduction of NEDC fuel consumption w.r.t. the normal production vehicle equipped with a 1.6 dm3, inline, 4 cylinder, 16v gasoline engine, whilst delivering quite similar vehicle performance.
At the heart of the system is an Engine Management System (EMS)-controlled electric centrifugal compressor, which increases volumetric efficiency at low and mid engine speeds, while peak power is increased by cam tuning. Unlike conventional turbo chargers, the electronically controlled compressor has no perceivable lag. Also, because it is an ‘On Demand’ transient device, it does not share the parasitic losses of a mechanically driven supercharger in Naturally Aspirated (N.A.) conditions.
Through the increase in specific torque output and re-optimisation of the transmission gearing, a 12% improvement in NEDC fuel economy at equal performance level was achieved, with no significant changes to the base engine.