Turbocharger: Description and Operation
Turbocharger DescriptionDescription and Operation
The turbocharger is used to increase the amount of air that enters the engine cylinders. This allows a proportional increase of fuel to be injected into the cylinders, resulting in increased power output, more complete combustion of fuel, and increased cooling of the cylinder heads, pistons, valves, and exhaust gas. This cooling effect helps extend engine life. Heat energy and pressures in the engine exhaust gas are utilized to drive the turbine. Exhaust gas is directed to the turbine housing. The turbine housing acts as a throat to direct the gas to the turbine wheel assembly. Since the compressor wheel is attached directly to the turbine wheel shaft, the compressor wheel rotates at the same speed as the turbine wheel. Clean air from the air cleaner is drawn into the compressor housing and wheel. The air is compressed and delivered through a crossover pipe to the engine air intake manifold, then into the cylinders.
The position of the turbocharger nozzle is controlled by the variable nozzle turbocharger (VNT) control module based on the command from the ECM. The VNT control module controls the turbocharger nozzle control solenoid that is installed to the turbocharger assembly. When the engine is low load condition, the turbocharger nozzles are moved to the open direction (A). When the engine is high load condition, the VNT control module commands the control solenoid to close the turbocharger nozzles (B), thus increasing the boost. The ECM will vary the desired boost target dependant upon requirements of the engine power output.
The charge air cooler also helps the performance of the engine. Pressurized air from the turbocharger have higher temperature than intake air, and charge air cooler cools the pressurized air. Cooling the intake air temperature makes the engine efficiency higher and engine power higher. The charge air cooler is located in the front of the radiator. From the charge air cooler, the air flows back into the intake manifold.