Performance and Emissions of a 4- Cylinder Gasoline Engine with Controlled Auto-Ignition

Advanced combustion modes such as Controlled Auto-Ignition or Homogeneous Charge Compression Ignition have been under much attention due to their ability to reduce both emissions and fuel consumption. Thus, this paper aims at demonstrating the achievement of Controlled Auto-Ignition combustion on a standard 4-cylinder gasoline engine with negative valve overlap (NVO) and analyzing its performance and emissions. The engine remained with substantially original components. The only major modification was the replacement of the camshafts for a new set of bespoke ones. The results showed a fair range of load and speed under CAI combustion with reduced brake specific consumption and ultra-low levels of NOx emissions. CO was also reduced, while HC emissions showed increased values. The results also point out some of the drawbacks of CAI combustion and the technological challenges of this advanced combustion process.