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Detergent additives in automotive gasoline fuel are mainly designed to reduce deposit formation on intake valves and fuel injectors, but it has been reported that some additives may contribute to CCD formation. Therefore, a standardized bench engine test method for CCDs needs to be developed in response to industry demands. Cooperative research between the Petroleum Association of Japan (PAJ) and the Japan Automobile Manufacturers Association, Inc. (JAMA), has led to the development of a 2.2L Honda engine dynamometer-based CCD test procedure to evaluate CCDs from fuel additives. Ten automobile manufacturers, nine petroleum companies and the Petroleum Energy Center joined the project, which underwent PAJ-JAMA round robin testing. This paper describes the CCD test development activities, which include the selection of an engine and the determination of the optimum test conditions and other test criteria.

Single cylinder engine testing was carried out to clearly understand the test results of multi-cylinder engines reported by the Diesel WG in JCAP (Japan Clean Air Program) (1), (2), (3) and (4). In this tests, engine specifications such as fuel injection pressure, nozzle hole diameter, turbo-charging pressure, EGR rate, and fuel properties such as 1-, 2-, 3-ring aromatics content, n-,i-paraffins content, and T90 were parametrically changed and their influence on the emissions were studied. PM emission generally increased in each engine condition with increased aromatic contents and T90. In particular, multi ring aromatics brought about large increases in PM regardless of the engine conditions. The influence of fuel properties on NOx emission is smaller than the influence on PM emission. Some other fuels that have various side chain structures of 1-ring aromatics, normal paraffins only and various naphthene contents were also investigated.

Effects of fuel distillation characteristics and cetane number on premixed charge compression ignition (PCCI) combustion were investigated for the purpose of reducing NOx and PM emissions from a direct injection diesel engine. The test engine had a hole type injection nozzle for conventional diesel combustion at high load operation. A low compression ratio and cooled EGR were applied to the test engine in order to reduce the compression temperature for avoiding pre-ignition. The investigation results show that, in the case of ignition control by EGR, a light fuel with lower distillation characteristics had an advantage of reducing smoke at higher loads. This means that high volatility fuel is effective in promoting lean mixture formation of fuel and air during the ignition delay. Moreover, lowering the cetane number was effective in reducing NOx emissions by suppression of combustion temperature.