In the CVCC engine, the air-fuel mixture formation in the auxiliary and main combustion chambers immediately prior to ignition is dependent on its geometrical and operating factors. Varying of such factors, as stated in SAE Papers (1) (2), leads to considerable changes in the engine's characteristics, namely, its fuel consumption and the exhaust emissions.
In this paper, we have obtained the combustion gas pressure and temperature diagrams of both main and auxiliary combustion chambers of a 1.5 litre, 4 cylinder CVCC engine and analyzed the diagrams by using the Mixture Formation Model, in order to study the characteristics of the generation of the exhaust emissions. As a result we found that the pattern of the pressure and temperature diagrams vary according to the air-fuel mixture formation and that the generation of emissions is in fact governed by the maximum combustion gas pressure and temperature, but the general tendency can also be shown by the temperature - time area ratio.
Even when indicated specific fuel consumption is maintained constant, variations in the geometrical and operating factors cause variations in temperature in the main combustion chamber and therefore similar variations in the average exhaust gas temperature immediately downstream of the exhaust valve, and affect the exhaust emission levels.