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A 2.0 liter displacement gasoline fueled car, with closed-loop control and 3-way catalyst, was adapted to operate on CNG (Compressed Natural Gas). A system allowing the detection and measurement of aldehydes, ketones, polycyclic aromatic hydrocarbons (PAH) and speciated organic materials was set up. Running on different fuels, such as CNG, gasoline and gasoline/oxygenates blends, tests were carried out according to US (FTP '75) and European (ECE+EUDC) procedures with and without the original 3-way catalytic converter. Apart from the absence of evaporative emissions because of the required closed delivery system, test results pointed out that CNG use yields substantial air toxics benefits in terms of regulated and, above all, unregulated emissions.

From september 1988 a fleet test started in Italy on urban buses equipped with a single ceramic monolith filter plus a by-pass and Diesel fuel burners for regeneration. The operation of the particulate trap, during the normal bus running in the city, has been assessed in three different ways: 1. Continuous control, by means of a data acquisition system purposely designed, of the main parameters affecting regeneration (i.e. time between consecutive regenerations, temperature in three selected zones in the filter during regeneration,filter loading); 2. Periodic control of smoke opacity of the bus measured, with and without the filter, under free acceleration and when bus is accelerating from 50 to 65 km/h on proving ground; 3. Particulate collection efficiency of the trap by using a dilution tunnel with the engine operated at the test bench. Information carried out from the fleet tests and additional information deriving from laboratory results were used for the system improvement.

In direct injection Diesel engines having a unit displacement less than 1 liter, the use of high compression ratios (19\20 instead of 16\17) is mandatory for solving cold smoke problems and reducing HC\NOx emissions. The increase of compression ratio however is associated to the increase of black smoke and specific fuel consumption. On the basis of systematic measurements of the main combustion quantities and 2-D computations of the air motion and spray development inside the cylinder, a re-entrant high compression ratio chamber was defined. Experimental results in terms of fuel consumption, black smoke and gaseous emissions are presented. The optimum squish-to-swirl ratio is discussed.

The impact of turbocharging on Diesel exhaust emissions has been investigated by studying, on a 4-cyl IDI Fiat engine different configurations including fuel injection optimization, exhaust gas recirculation and oxidant catalysts. The experimental results obtained during bench and chassis dynamometer tests were compared with the same tests performed on the naturally aspirated 4-cyl engine. Mathematical models were used in order to identify the regions giving the maximum contribution to regulated emissions. Particulate and organic adsorbed compounds were also measured. It appears that turbocharging can represent a reasonably good approach in order to achieve low levels of regulated emissions and particulates associated with high fuel economy.

Carbonaceous material associated with potent carcinogens such as 3-4 benz(a)pyrene (BaP) and other polynuclear aromatic (PNA) hydrocarbons constitutes by far the greatest part of the particulate found in the exhaust gases of an internal combustion engine. The probable precursors of carbon particles are radicals formed in the incomplete combustion zone while their nucleation is made possible by ions originating in the flame. Ion current instantaneous values were measured by means of a modified Langmuir's probe, thus calculating thickness and speed of the flame in an engine cylinder. Relations between ion current and collected soot weight were examined. Fuel quality and additive influences over carbon and PNA formation were obtained.