MCLTC Demonstrates Decreased Peak of Pressure Rise and Soot: PCI combustion simultaneously reduces both NOx and particulate emissions but works only under certain engine operating conditions, generally in the low-load range. Also, ignition delay is extended with advanced fuel injection timing so that the injected fuel has sufficient time to mix prior to the start of combustion. Thus, the initial combustion rate becomes high, causing the rate of pressure rise to increase. Hence, combustion becomes noisy. To resolve these issues associated with PCI combustion, researchers at the Japan Automobile Research Institute (JARI) conceptualized “mixing-controlled low-temperature combustion,” (MCLTC). Pilot fuel is injected at relatively low pressure ahead of main fuel injection at high pressure. This chapter describes the MCLTC concept, engine test results, and validation of the concept according to numerical analysis.