High efficiency stoichiometric spark ignition engines

Nowadays most passenger cars are equipped with spark ignition engines with a three way catalyst. Thus, the improvement of fuel consumption of this type of engine represents a very attractive goal. In fact, it may cause a reduction of pollutant emission, and simultaneously it may give a contribution to the lowering of global CO2 production. In this paper, a strategy to control the combustion process of stoichiometric spark ignition engines is described. It is based on the adoption of Exhaust Gas Recycle (EGR) in high compression ratio engines. The tests carried out have shown that EGR can control the knock, even at Wide Open Throttle (WOT), with a compression ratio of about 13.5. Improvements of efficiency higher than 10%, at different loads and speeds, have been achieved by the adoption of this technique. Similar improvements have been obtained for CO, while more substantial reductions have been measured for NOx.