1 Less is more

The issue of low CO₂ emissions is becoming an increasingly important factor for customers when they buy a new vehicle. Manufacturers also face the prospect of fines if the CO₂ emissions of their vehicle fleet exceed future limits set at EU level. Rapid solutions are therefore called for - or, more precisely, scalable solutions that can be implemented quickly - because different vehicles and markets require different approaches. In the light of these developments, the Automotive Group at Continental has developed solution packages for highly efficient optimisation. The list of innovations begins at engine component level and extends to power units, the drive system, electrification and the man-machine interface, as well as close integration of the driver and semi-autonomous assistance systems such as Adaptive Cruise Control (ACC).

Engine size reduction (Downsizing) through exhaust turbocharging

In terms of technical complexity, turbocharging (TC) an engine in conjunction with direct injection (DI) is by far the most effective strategy for increasing its efficiency. By using DI and TC, the fuel consumption of a gasoline engine can be reduced by about 20% compared with its normally aspirated counterpart assuming the same engine power level. Driven by CO₂ emission regulation, the proportion of turbocharged gasoline engines is set to rise sharply.

In order to fulfil the TC requirements for fuel efficient passenger cars to optimum effect, Continental has developed a new generation of TC. Using narrowly graduated turbine wheel diameters ranging from 29.9 to 59.6 mm and milled compressor wheels, the TC can be optimally adapted to a broad range of car engine sizes. The first series — the SK1 with a turbine wheel diameter of 30 to 38 mm - is suitable for smaller vehicles (Figure 1). Water-cooled TC with waste gate covers the performance range up to about 100 kW and is designed for a maximum exhaust gas temperature of 1050°C. This is important in that the high temperature resistance of the turbine makes it unnecessary to enrich the air/fuel-mixture under engine full load to protect the component.

During development, the main functions of the TC underwent a radical, independent reassessment. The design features of the modular TC structure, for example, have been logically designed for thermodynamic efficiency, reliability and process-optimised assembly. In terms of CO₂ emission reduction, electrical operation of the waste gate plays an important role because it enables, amongst other things, good transient performance even at low engine speed.