### Analysis of Indicated Pressure Diagrams in Recent Literature  
Referring to two engine subsystems controlled in the present study (fuel injection and EGR systems), the analysis of the available literature published in recent years confirms the above-mentioned fact, as indicated pressure diagrams and heat release curves are widely presented but their further processing is not generally applied. The investigations on alternative fuels can be supported by in-cylinder measurements, as discussed in Reference [2] considering the influence of diesel injection pressure and timing in a dual-fuel large displacement (7.8 L) turbocharged engine. A premixed mixture of methanol and air was ignited by the direct injection of diesel oil. The increase of diesel injection pressure led to rising levels of peak pressure, maximum heat release and combustion noise, reducing ignition delay and combustion duration. Similar effects were observed when advancing injection timing, except for ignition delay. Natural gas was tested in Reference [3], where a single cylinder engine (2.0 L) derived from a heavy-duty diesel unit was modified to compare different mixture strategies (stoichiometric and lean conditions) and ignition modes (spark or diesel pilot). A mixture between natural gas and hydrogen was also considered. The rate of heat release was evaluated to assess the development of the combustion process for the different conditions at part and full load, referring to changes in ignition delay, combustion duration and maximum heat release. Combustion control in a dual fuel engine was also investigated in Reference [4]. Two load levels were tested in a single cylinder engine (0.51 L), in order to optimize the amount of natural gas and diesel when comparing strategies for the management of indicated mean effective pressure (imep) and centre of combustion. Maximum pressure and rate of heat release were considered in order to assess the effectiveness of impe and \(\theta_{50}\) control. Biofuel obtained from canola oil was studied in Reference [5], where diesel oil, a B20 blend and neat canola oil were compared through measurements made in four different load levels at a constant speed on a 2.0 L common rail diesel engine. Lower values of maximum pressure and heat release were observed when using alternative fuel, while the oxygen content of canola oil led to a reduction of ignition delay. The effects of adding ethylene glycol in different proportion (from 5% to 15%) to diesel oil were studied in Reference [6], considering a common rail diesel engine with a 7.8 L displacement. Tests were developed for six levels of engine load at the rotational speed corresponding to rated torque. The most significant variations were observed at intermediate and high load, where the addition of ethylene glycol led to an increase in the maximum pressure, the rate of heat release and pressure rise rate, reducing ignition delay and combustion duration. The development of advanced combustion mode is also based on heat release analysis, as presented in Reference [7], where a reactivity controlled compression ignition engine was considered. In this case, an opposite influence of the increase of fuel pressure injection, compared to the expected behaviour, was observed, resulting in lower maximum values of heat release and peak pressure, longer ignition delay and combustion duration. These outcomes were the effects of the reduced spray penetration related to the lower average diameter of fuel droplets and the worst combustion propagation to gasoline. In Reference [8], the rate of heat release was used in order to reduce fuel consumption and combustion noise when applying multiple fuel injection strategies to a single cylinder diesel engine, featuring pre-mixed combustion, with a displacement of 0.55 L. The rate of heat release and combustion noise were modelled, in order to design the injection strategies when actuating from two to five events, sharing the amount of injected fuel among them in order to minimize noise while achieving the highest thermal efficiency.