Experimental investigation on cold start and warm-up phases for an ethanol fueled SI engine.

Engine operation during the initial warm-up period is characterized by pronounced thermal non-uniformities, which have a direct impact on fuel efficiency, combustion stability, tailpipe emissions and engine long-term reliability. For these reasons, accelerating the warm-up process represents an effective strategy to improve both environmental impact and overall engine performance. This paper presents an experimental study carried out on a 1.2 liter, naturally aspiered, four-cylinder SI engine equipped with a Port Fuel Injection (PFI) system. The engine is fueled with standard gasoline and an ethanol-gasoline blend containing 30% ethanol by volume (E30), with the aim of assessing the influence of fuel formulation on thermal evolution after a cold start. Each test begins with the engine at ambient temperature and is continued until thermal equilibrium is established. Experiments are carried out at a single steady operating point of 2000 rpm and 20 Nm, selected to reproduce representative conditions of typical warm-up operation. The investigation primarily addresses the time required for the engine to reach stable thermal conditions and evaluates the corresponding variations in many performance metrics. Overall, the study seeks to deepen the experimental understanding of how ethanol enrichment in gasoline affects the warm-up dynamics of spark-ignition engines, providing insight into behavior under cold-start operation.