A comparative test of fuel economy and emission characteristics was carried out on a 1.5 L turbocharged direct injection gasoline engine using different technologies of exhaust gas recirculation(EGR) and in-cylinder air diluted combustion. Results show that compared with the original engine

the use of an air diluted combustion system can reduce fuel consumption by 6.2% at an air dilution rate of 49.5%

while with the EGR system

fuel consumption can be improved by 4.2% at a dilution rate of 20.5%. At the same dilution rate

the EGR system can use a more advanced ignition timing to achieve a better combustion

while the polytrophic exponent increment caused by the air diluted combustion system makes the engine more economical than the EGR system

and the engine is more tolerant to air dilution. When the air dilution rate of the air diluted combustion system is 11%

the engine emissions reach the highest level

and then decrease with the increase of air dilution rate. As for the EGR system

as the dilution rate increases

NOx emissions continue to drop significantly. In addition

when using the air diluted combustion system

CO emissions will be much lower than the original engine

while for the EGR system

CO emissions slightly decrease with the increase of dilution rate. Moreover

the use of air diluted combustion system can make HC emissions lower than the EGR system

and when the air dilution rate increases from 49.5% to 68.0%

HC emissions will increase significantly.