With increasing CO2-emissions and reducing oil resources fuel economy improvement of passenger car S.I. engines has become a major issue. A promising approach is the reduction of pumping and friction losses by shifting the operation point to lower engine speed/higher load by engine down sizing. This requires small-supercharged engines with a high specific power (kW/litre). To improve part load efficiency and to avoid full load knocking these engines must have a Variable Compression Ratio (VCR). A down-sized, highly boosted engine with variable compression ratio has a 30% fuel saving potential compared to a model year 1998 vehicle and has simultaneously low exhaust emission levels as 'a=1.0-concept' with the well developed TWC technology. The goal of this project is to demonstrate these benefits through single-cylinder investigations with different VCR mechanisms as well as multi-cylinder test bench and in-vehicle investigations. As a final output, the industrial feasibility and the costs of such an engine concept shall be demonstrated.
The outcome of the project can be summarized as follows: Three different VCR concepts have been designed and manufactured. In parallel to the concept phase, a literature and patent study, regarding existing VCR-concepts has been accomplished by the consortium. In addition to the hardware designs, the combustion calculation for VCR engines, supported by single cylinder investigations have been conducted. Based on this results, 2 full-size validator engines have been produced and installed into validator vehicles and were tested in the MVEG cycle. Depending on the VCR system used and the degree of down sizing fuel improvement of up to 27% were measured. The fuel improvement resulting only on the optimal compression ratio depending of load and speed come up to 8% (w./o. downsizing effect).
Funding SchemeCSC - Cost-sharing contracts
221 00 Lund
78943 Velizy Villacoublay
OX16 7XS Banbury
405 31 Goeteborg