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Stronger ignition sources become more favorable under extreme lean/EGR conditions. Under those conditions, the reduced pumping loss and low combustion temperature can contribute to further engine efficiency improvement for spark ignited engines. Multicoil ignition system can enhance ignition energy as well as modulate discharge profile. The ignition energy can either be deployed through single spark gap to enhance the ignition capability of the plasma channel, or be distributed to multiple ignition sites to establish multiple flame kernels to secure flame kernel initiation. The multiple ignition coils used for energy distribution ignition strategy also consume more power, in order to maintain the stable operation of the engine under lean operation limit. In this paper, efficacy of concentrated and distributed multicoil ignition strategies were investigated on a spark ignited inline 4-cylinder production engine using a three-ignition-coil pack.

The present work aims at optimizing diesel engine combustion efficiency with optimized water injection strategy. The engine had been modified based on a two-cylinder mechanical pump diesel engine into common rail diesel engine with capability of direct water injection. The direct water injection system was designed and manufactured independently. An air-fluid booster was utilized to establish the water injection pressure up to 40MPa. Customized diesel injector was selected to be used as water injector in this study. Water injection strategy was optimized in detail with injection timing around TDC which ranges from 12°CA BTDC to -5°CA BTDC under 10 bar IMEP. The engine efficiency can be improved under selected water injection strategy due to the increment of work fluid in the combustion chamber. Moreover, the nitric oxides emissions show decrement around 10%.

The CO2 reduction request for automotive industry promotes the efforts on the engine thermal efficiency improvement. The goal of this research is to improve the thermal efficiency on an extremely downsized 3-cylinder 1.0 L turbocharged gasoline direct injection engine. Effects of compression ratio, exhaust gas recirculation (EGR), valve timing and viscosity of oil on fuel economy were studied. The results show that increasing compression ratio, from 9.6 to 12, can improve fuel economy at relative low load (below 12 bar BMEP), but has a negative effect at high load due to increased knock intensity. EGR can significantly reduce the pumping loss at low load, optimize combustion phase and reduce exhaust gas temperature. Therefore, the fuel consumption is reduced at all test points. The average brake thermal efficiency (BTE) benefit percentage is 3.47% with 9.6 compression ratio and 5.33 % with 12 compression ratio.