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Experimental Design methodologies have been applied in conjunction with objective functions for the optimization of the internal geometry of a rear muffler of a subcompact car equipped with a 1.4 liters displacement s.i. turbocharged engine. The muffler also features an innovative variable geometry design. The definition of an objective function summarising the silencing capability of the muffler has been driving the optimization process with the aim to reduce the tailpipe noise while maintaining acceptable pressure losses and complying with severe space constraints. Design of Experiments techniques for the reduction of experimental plans have been shown to be extremely effective to find out the optimum values of the design parameters, allowing a remarkable reduction of the time required by the design process in comparison with full factorial designs.

Different diagnostic techniques were experimentally tested on a common rail automotive 4 cylinder diesel engine in order to evaluate their capabilities to fulfill the California Air Resources Board (CARB) requirements concerning the monitoring of fuel injected quantity and timing. First, a comprehensive investigation on the sensitivity of pollutant emissions to fuel injection quantity and timing variations was carried out over 9 different engine operating points, representative of the FTP75 driving cycle: fuel injected quantity and injection timing were varied on a single cylinder at a time, until OBD thresholds were exceeded, while monitoring engine emissions, in-cylinder pressures and instantaneous crankshaft revolution speed.

Numerical simulation can be effectively used to reduce the experimental tests which are nowadays required for the analysis and calibration of engine control and diagnostic systems. In particular in this paper the use of a one-dimensional fluid-dynamic engine model of an 8 cylinders high-performance s.i. engine coupled with a vehicle and driveline model to simulate the effects of misfire events on the engine angular speed is described. Furthermore, the effect of cycle-to-cycle combustion variability was also evaluated, in order to take into account variations in the combustion process that can substantially increase the engine speed fluctuations under normal operating conditions, thus hindering the misfire detection. Finally, a comparison with experimental data obtained on a chassis dynamometer was carried out. After this accuracy assessment, the numerical simulation could be used to analyze different techniques for misfire detection, thus reducing the required experimental tests.

The unsteady flow effects in two different close coupled catalytic converters were investigated in order to achieve a better understanding of the steady state experimental tests which are usually performed to evaluate a flow distribution. Firstly the validity of a CFD model was achieved through a comparison of some steady state simulations with the results of HWA experimental measurements. Several different formulations of the uniformity index, that were found in literature, were then compared, trying to highlight the strengths and shortcomings of each one. Further information was derived from a comparison of the two catalysts that were tested to achieve a general methodology that would be useful for future analysis. Finally, a new approach to evaluate the flow distribution using a steady state analysis was proposed by comparing the results of a transient simulation that was obtained for a whole engine cycle.

The influence of pilot injection timing and quantity on soot, NOx, combustion noise and bsfc has been analyzed on a passenger car DI Diesel engine prototype equipped with a common rail fuel injection system. The investigated engine operating points were 1500/5, 2000/2, 2500/8 rpm/bar, which are quite typical of EC driving cycles. For each of these operating conditions, the pilot injection quantity was varied by up to 15% of the total injected quantity and the pilot injection timing was varied between 32° and 1° crank angle degrees. The principal combustion characteristics were determined on the basis of the heat release, and a thorough statistical analysis was performed to infer the correlation between the combustion parameters and soot and NOx emissions.

The potential of numerical simulation in the analysis of the dynamic transient response of a vehicle during tip-in manoeuvres has been evaluated. The dynamic behavior of the driveline of a typical European gasoline car was analyzed under a sharp throttle input. A one-dimensional fluid dynamic model of the engine was realized for the simulation of the input torque; afterwards, it was coupled with a driveline and vehicle model implemented in Matlab-Simulink environment. After a detailed validation process based on several sets of experimental data, the engine and vehicle coupled simulation was used to evaluate different control strategies during tip-in manoeuvres aiming to enhance the vehicle driveability.

The application of computational methods for the development of the whole engine-vehicle system has been evaluated in this paper, to highlight the potential of computer simulation techniques applied to the analysis of engine-vehicle matching. First, engine performance was simulated using a one-dimensional fluid dynamic code, and predicted data were compared to experimental results, to assess the accuracy of the engine computer model not only as far as gross engine performance parameters are concerned, but also for the prediction of pressure values at several locations inside the engine. The simulation was also extended to the whole engine operating range, including part-load operating conditions. Afterwards, a vehicle simulation code was employed, to predict vehicle performance and fuel consumption.

The application of computational methods for the development of a tuned exhaust system for a small two stroke scooter engine has here been evaluated. A single dimension fluid dynamic code has been employed, in order to simulate engine performances at full load with a prototype exhaust system, and data predicted from computer simulation have been compared with experimental results, obtained using a test rig and a data acquisition system specifically designed for small two-stroke engines. In this way the accuracy of the computer model has been assessed not only as far as gross engine performance parameters are concerned, but also concerning the prediction of pressure values in several locations inside the engine and the exhaust system. Finally, computer simulation techniques have been applied to the development of the prototype exhaust system, and have been proved to be powerful and effective techniques to identify the modifications required to obtain the engine performance targets.