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A test procedure was set up in our laboratories to evaluate the propensity of fuels and lubricating oils towards the soot accumulation in Diesel Particulate Filters. The experimental work was carried out with the use of a passenger car diesel engine, retrofitted with an aftertreatment system composed by an oxidation catalyst and a DPF. The soot propensity was evaluated by means of repeated measurements of differential exhaust backpressure gradient, during a running period at mid load and speed. The specific fuel consumption gradient was also measured to find a correlation between both the variables. After each soot loading period, a burning off period at full load was operated for the purpose of filter regeneration. A two-phase experiment was undertaken to assess repeatability and discrimination capability of the test procedure. During the first experimental phase, repeated tests were conducted on a fuel matrix containing some surrogate fuels.

This work was conducted in order to study the effect of Combustion Chamber Deposits (CCD) on engine-out hydrocarbon emissions. A bench engine test based on the CEC-F-20 test procedure was used to accumulate CCD. The experiments were performed on a 2.0 L, four-cylinder engine with multipoint fuel injection. All measurements were carried out under steady state operating conditions at full load on the engine. The measurement of exhaust hydrocarbons was accomplished with a fast-response FID analyser, with the sample probe being installed close to the exhaust valves in the exhaust port of cylinder #1 and #4, respectively. Interpretation of the measurements was based on the typical hydrocarbon curve measured by the fast FID during the exhaust phase of the combustion cycle. In order to emphasize the CCD effect, three pure component fuels of differing volatilities were used. Test results indicated that CCD gave an increase of total HC amount.

An engine bench test has been developed to measure the total amount of liquid fuel wetting the intake walls of a S.I. port fuel injected engine under steady-state conditions. A four cylinder engine equipped with a double injection system was been utilized. One injection system was fed with 2-methyl-2-butene, which did not produce liquid fuel deposit on the intake manifold, the other injection system was fed with different types of fuel and both systems were set at the stoichiometric air-fuel ratio. Putting the injection commutation on, the 2-methyl-2-butene is suddenly replaced by the fuel of the second injection system. An oxygen sensor (UEGO type) monitors the air-fuel ratio excursion due to the injection commutation and the test runs until the A/F re-establishment at the stoichiometric level.