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This paper presents the main conclusions of the project carried out by the Department of Advanced Studies in Control of Engines of RENAULT and the group IMST of the Departamento de Termodinámica Aplicada de la Universidad Politécnica de Valencia. The main objectives of this Project was: The characterization of the camless engine prototype by means of the modeling for different engine speeds and loads. The determination of the influence of the external operation conditions on the performance of a prototype of a camless engine, by means of the calculation with the program ECARD.

The main objective of the work which is presented is to optimize the breathing and torque in the whole operational speed range for multi-valve engines, without any variable system (valve timing or induction), by the application of both computational (modelling methodologies) and experimental (steady flow rig and engine test bench) means. The study has been performed on a typical 1.8-litre multi-valve engine which developed a standard maximum torque of 146.5 Nm at 4500 rpm. After modification, the optimized performance was 161 Nm at 4250 rpm (an improvement of approximately 10%).

In this paper, the results and main conclusions of a R&D project carried out to achieve the highest level of performance in a 125cc. 2-S engine for a World Championship racing motorcycle are presented and discussed. Both computational (Modelling Techniques) and experimental (steady flow rig and motorcycle roller test bench) means have been combined, trying to accomplish the highest degree of optimization. An important improvement in the engine's performance was obtained as a result. The paper also describes in some detail the organization of the study, the possible strategy of optimization, the characteristics of the new computer code used to perform the calculations of these very difficult engines, and the experimental measurements. With the objective being to achieve the highest level of performance in a 125 cc. 2-Stroke engine for a World Championship racing motorcycle, a wide R&D project has been carried out by the use of experimental and computational techniques.

This article sets global rules for the design of the different elements of the intake system for a wide range of 4-s. i.c.e, examining the different phenomena related with the gas exchange process. With this objective, a broad analysis of a set of very different automotive engines was carried out, using a full wave action model developed by this same research group and widely checked by comparison with experimental results. The design criteria presented in the paper have been extensively and successfully applied in different development projects carried out for several automotive engine companies.

In this paper the results and main conclusions of a study concerning BGF at low loads, its relationship with valve timing and load, and its influence on engine instability and emissions, are presented. The study covered a wide range of load and valve timings for both intake and exhaust valves. Measured values of engine performance, emissions and instability were used. BGF was estimated by a global engine code based on a full wave action model. The good correlation found between calculated BGF with measured parameters proves the capability of wave action models to predict the influence of design modifications on engine performance at low loads. A very interesting relationship, found among BGF, volumetric efficiency, IVO and permeability is presented. As well, the relationship between BGF and manifold pressure, with engine instability and NOx emissions are discussed and a correction of the manifold pressure which describes very well both aspects of engine performance is presented.