Effects of Combustion Chamber Deposits, Compression Ratio and Combustion Chamber Design on Power and Emissions in Spark-Ignition Engines

Experimental results from three different single cylinder engines using the same fuel at different operating conditions and at different stages of build-up of combustion chamber deposits (CCD) are reported. Two of these engines have the same pent-roof, four-valve head but different compression ratios while the other has two valves and a much slower burn-rate. Increasing the compression ratio increases HC and NOx emissions correlate very well with peak engine pressure. The effects of CCD on combustion rate, power and emissions depend greatly on engine design and also on operating conditions.