Hybrid power systems demand higher thermal efficiency from engines, and Atkinson cycle and exhaust gas recirculation (EGR) technology have become key breakthroughs.

1. Atkinson cycle principle and application

Working principle: By delaying the closing of the intake valve, the expansion ratio is greater than the compression ratio. For example, the Toyota THS system uses an Atkinson cycle engine with an effective thermal efficiency of 41%, which is 6% higher than the traditional Otto cycle.

VVT-i system optimization: By hydraulic control of the intake camshaft phase, the engine achieves Miller cycle at low speeds and switches to Otto cycle at high speeds. Actual test data shows that a certain vehicle model reduces fuel consumption by 8% under NEDC conditions.

2. Progress in Exhaust Gas Recirculation Technology

Low pressure EGR system: introducing exhaust gas from the turbine into the intake manifold to reduce combustion temperature. After adopting this technology, a certain 2.0L engine reduced NOx emissions by 35% and fuel consumption rate by 3%.

Cooling EGR technology: By cooling the EGR gas through an intercooler, the anti knock performance is further enhanced. Under WLTP conditions, the CO ₂ emissions of a certain hybrid vehicle decreased to 95g/km.