Experiences in improving the Low end performance of a Multi Purpose Vehicle (MPV) equipped with a common rail Diesel engine. 2009-28-0008

Continually increasing customer demands and legislative Requirements regarding fuel economy, emissions, Performance, drive ability and comfort need to be met by every OEM's developing vehicles worldwide. There is a serious pressure to reduce CO2 emission from automotive application which contributes to around 15.9% of the total CO2 production based on the Surveys done time to time. In a developing market like India, many foreign players are entering with lots of option for offering to this market. The parameters of prime importance here are fuel efficiency with good drive ability and at the same time affordable price. Diesel engines are finding these benefits and attracting the buyer over its counterpart (Gasoline). The road condition and the driving pattern in India compared with developed countries differ to a major extent. In India, the Low speed uses are predominating in Cities and in Ghats. This leads to frequent gear shifting thus reducing driver comfort and loss of fuel economy. In Diesel engine, the low end response of engine plays a vital role in reducing the gear downshifting in both city and Ghats drive. Thus, can take a potential saving of fuel and driving comfort. However, the low engine speed torque is limited by the air availability. With the upcoming trends towards downsizing, the swept volume of the engine is coming down. Hence, the air taken by the engine at low speed and low BMEP is limited. The black smoke formation is more prominent in lower engine speed. Hence, simultaneous increase of low end performance without any design changes and cost becomes a challenge.

In this paper, Low end performance improvement of a Multi purpose Vehicle (MPV) equipped with a 2.5L common rail diesel engine is presented. The efforts for the low end performance improvements were made from both vehicle (Gear box, axle ratio, and tyre) and engine side (improvement of low end torque) by exploring the common rail potential. Iteration of different gear ratio combination, final axle ratio and tyre dynamic rolling radius were done. To reduce the number of Experiments, AVL CRUISE software was used to minimize the iteration. Torque at full load in lower engine speed was improved by introducing the early pilot with relatively

Higher quantity. However, in the part load, this pilot quantity was split into two successive pilot injections. Selection of pilot separation was optimized in such a way that Noise and Smoke levels are maintained or improved. Engine level trials were conducted with cylinder pressure and Noise Measurement with AVL Indicom. The Concept of Design of experiment (DOE) was used to minimize the number of iteration and for analysis of results was done using commercially available MINITAB software. The vehicle performance, pass by noise were found to be improved.