PCI Combustion Demonstrates Potential for Cogeneration Application: Compared to use in automotive applications, natural gas engines used for cogeneration applications operate over a relatively narrow range of speed and load. Since premix compression ignition (PCI) combustion effectively reduces exhaust emissions and fuel consumption but can only be used under certain engine operating conditions, natural gas engines for cogeneration may be good candidates for application of PCI combustion to improve both fuel economy and exhaust emissions. Researchers at the Japan Gas Association and Keio University demonstrated PCI combustion in a 3.318-liter, four-cylinder natural gas engine with an external supercharger and an electric heater for intake system.