An experimental study was carried out on a 4-cylinder turbocharged and inter-cooled diesel engine with 3.8 L displacement to reveal the influence of exhaust pressure on the engine performances. During the engine tests

the turbocharger of the engine was removed

and the intake and exhaust pressures of the engine were controlled directly by a self-made pressure control system. Experimental results show that the exhaust pressure has little influence on the cylinder pressure and maximum combustion pressure changes with crankshaft angle. The air mass flow rate has a certain linear relationship with exhaust pressure：The air mass flow rate will be decreased by 1.2~2.0 kg/h

accounting for 0.4%~0.7% of the original value

when the exhaust pressure increases by 10 kPa. There is a linear relationship between the exhaust temperature and exhaust pressure. The exhaust temperature will be increased by 4.0~4.7 ℃ when the exhaust pressure increases by 10 kPa. Increasing exhaust pressure makes the engine power and fuel economy seriously deteriorated resulting in decrease in brake torque by 2.3~3.1 N•m

accounting for 1.0%~1.9% of the original value and increase in brake specific fuel consumption by 2.8~7.1 g/(kW•h)

 accounting for 1.4%~3.3% of the original value

when the exhaust pressure increases by 10 kPa. Simulations show that an increase in exhaust pressure makes the pumping loss increased so that the indicated mean effective pressure will be decreased by 9.8~10.7 kPa

accounting for about 13% of the original value

when the exhaust pressure increases by 10 kPa.