Search Results

Driving fun - one of the major thrills expected by the buyers of high-performance cars - must be absolutely preserved despite all the measures required to further reduce the car's exhaust emissions and fuel consumption. Powerful engines with high BMEP levels require large unrestricted inlet and outlet valve diameters and lifts as well as a wide camshaft phasing range at least on the intake side. In terms of exhaust emissions and fuel economy such an engine layout is rather unfavourable. Its inherent drawbacks, however, can be compensated by providing for what might be called a “two-in-one” configuration which combines a low-emission concept including intake-valve lift shifting and exhaust-camshaft phasing with a high-performance-engine concept complete with a wide intake camshaft phasing range and large intake valve lifts and a Varioram intake system. With this basic layout, even high-performance sports cars are able of falling below the current ULEV limits.

For the measurement of exhaust emissions, Constant Volume Sampling (CVS) technology is recommended by legislation and has proven its practical capability in the past. However, the introduction of new low emission standards has raised questions regarding the accuracy and variability of the CVS system when measuring very low emission levels. This paper will show that CVS has the potential to achieve sufficient precision for certification of SULEV concepts. Thus, there is no need for the introduction of new test methods involving high cost. An analysis of the CVS basic equations indicates the importance of the Dilution Factor (DF) for calculating true mass emissions. A test series will demonstrate that, by adjusting the dilution and using state of the art analyzers, the consistency of exhaust results is comparable with those of LEV concepts, measured with conventional CVS systems and former standard analyzers.