Transient Combustion Noise of Diesel Engines

Despite the progress accomplished by car makers these last years, combustion noise is still the main noise issue for Diesel engine. New standards are more and more restrictive in terms of emissions whereas drivers ask for engines with more fun to drive without increase of fuel consumption. In this context and since NVH is an important factor in quality perception, engine calibration must also insure a good or at least acceptable combustion noise.
As far as steady state running conditions are considered, combustion noise of most of recent engines is rather well accepted, in comparison with combustion noise of the first Diesel engines. Nonetheless, the perception during transient running conditions is still often criticized by customers.

PSA Peugeot Citroën has tuned the combustion noise of its last engines using an intern tool: Pcyl2Note. This is an in home developed software which is used to asses the combustion noise quality in steady state running conditions. For the last few years, Pcyl2Note was adapted to transient running conditions. The transient combustion noise quality can be evaluated during the engine calibration phase in the form of curves representing the evolution of the Pcyl2Note note versus time. Furthermore, criteria of acceptation have been established to help comparison of different calibrations.