###### Abstract  
Indicated pressure diagrams were measured during experimental campaigns on the control of fuel injection, turbocharging and hybrid exhaust gas recirculation systems in an automotive downsized diesel engine. Three-part load operating conditions were selected for four test sets, where strategies aimed at the reduction of NOX emissions and fuel consumption, limiting penalties in soot emissions and combustion noise were applied to the selected systems. Processing of in-cylinder pressure signal, its first derivative and curves of the rate of heat release allowed us to evaluate seven parameters related to the combustion centre and duration, maximum values of pressure, heat release and its first derivative, heat released in the premixed phase and a combustion noise indicator. Relationships between these quantities and engine operating, energy and environmental parameters were then obtained by referring to the four test sets. In the paper, the most significant links are presented and discussed, aiming at a better understanding of the influence of control variables on the combustion process and the effects on engine behaviour. The proposed methodology proved to be a consistent tool for this analysis, useful for supporting the application of alternative fuels or advanced combustion modes.  
diesel engine; in-cylinder pressure diagrams; rate of heat release; combustion parameters; high and low-pressure EGR; variable geometry turbine control; rail pressure control; NOX and soot emissions; fuel consumption +
Footnote †: journal: Applied  
on peculiar aspects such as the combustion process and its relationship with operating, energy and environmental parameters.  
Taking into account this point, the paper presents an experimental study on the analysis of changes in a wide set of combustion parameters when applying control strategies to fuel injection, turbocharging and hybrid exhaust gas recirculation (EGR) systems in an automotive diesel engine with a total displacement of 1.248 dm\({}^{3}\). Combustion parameters were obtained through proper processing of indicated pressure diagrams, the first derivative of the in-cylinder pressure signal and rate of heat release (RoHR) curves. Relationships between these parameters, fuel consumption and emissions were developed in order to describe the observed variations, offering numerical instruments for the modelling of detected trends and the development of suitable control strategies aiming at the achievement of proper goals involving selected variables.  
Innovative aspects of the study are related to the definition of a database wider than what is commonly available and investigated, as few combustion parameters are usually calculated to allow a qualitative analysis while neglecting reciprocal interactions. On the other hand, the experimental campaigns involved three part-load working conditions and a large number of different operating modes resulting from a combination of selected control variables, focusing on a downsized engine.  
While a previous paper [1] was focused on the influence of the EGR rate and variable nozzle turbine (VNT) control on engine quantities, pressure diagrams and combustion parameters, this paper refers to whole sets of experimental campaigns, thus including the effects of rail pressure management. A further goal was to identify similarities in the influence of the three sub-systems control on observed trends of measured parameters.