BYD introduced its dual-platform strategy with DM(dual mode) hybrid technology recently, including the DM-p platform: the super power version; the DM-i platform: the ultra-low fuel consumption version. According to the fuel consumption requirement of DM-i plug-in hybrid architecture, a brand new 1.5NA high-efficiency engine was developed . This engine can reach a peak of 43% brake thermal efficiency. Combined with high power electric motor, the full system can guarantee low fuel consumption at various vehicle speeds, while maintaining fast accelerations. To reach such high thermal efficiency, the engine technological choice consisted in the association of: high compression ratio of 15.5, long stroke, Atkinson cycle, high tumble port, cooled EGR and high energy ignition. The high compression ratio implies knock and pre-ignition mitigations, which is performed through EGR and piston cooling jets. A lot of work was also done on the software side to optimize knock and pre-ignition control. The thermal management was completely redesigned. The use of electrical water pump, associated with two thermostats (one electrical and one traditional wax type) made it possible to implement split cooling. Associated with intelligent control of thermal needs under all working conditions, the benefits were: faster engine warm-up, improved fuel economy and pollutant emissions reduction. To push the efficiency even higher, friction was reduced to its minimum through different measures: 0W-20 oil, low tension piston ring, DLC coating, two-stage variable displacement oil pump and electrification of the accessories. With the combination of these technologies, and further optimization, the new 1.5NA engine achieved top level thermal efficiency in its class. Applying this engine to the DM-i plug-in hybrid architecture, the vehicle charge-sustaining fuel consumption decreased by 41% compared to the previous generation.