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Traditional power train development work is concentrated mainly on test bed and on chassis dyno. Though we can simulate a lot of real world conditions on testbed and chassis dyno today, on road application work willis gaining more attention. This means that strategies and tools for invehicle testing under real world conditions are becoming more important. Emission, performance, fuel economy, combustion noise and driving comfort are linked to combustion quality, i.e. quality of fuel mixture preparation and flame propagation. The known testing and research equipment is only partly or not at all applicable for in-vehicle development work. New tools for on the road testing are required. Following, a general view on in-vehicle power train testing will be given. Additionally, new ways to investigate cylinder and cycle specific soot formation in GDI engines with fiber optic tools will be presented.

Current legislation trends for Heavy Duty and Off-Road engines show an increased contribution of transient cycles for engine homologation. For the HD EURO 3 and EURO 4 regulations, effective from the year 2000 and 2005 respectively, the new ESC (European Steady State Cycle), the new ETC (European Transient Cycle) and also the new ELR (European Load Response) Opacity test must be carried out, as well as the old ECE R 24 test procedure. A highly sophisticated new Opacimeter, designed according to the latest state of the art, is described. This instrument, certified to conform to the old and new legal homologation test procedures and to international standards, has proved to be also a powerful tool for engine R & D as well as production testing, as shown in several application examples.

The performance of SI engines is substantially influenced by the degree of fuel atomization that occurs within the mixture preparation system. With a measuring device, based on laser Sight diffraction, it is possible to determine droplet size spectra with high temporal and spatial resolution, even if the droplets are moving with high velocity. However, with such a measuring device, the influence of density gradients within the measuring volume, as that created by fuel vapor or temperature differences, can be critical and must be taken into consideration to provide satisfactory results. The degree of atomization depends on the engine operating conditions, namely engine speed and load.