Chapter 13 Exhaust Systems 297 Copyright Goodheart-Willcox Co., Inc. Constant Geometry Turbocharger Operation In a running diesel engine, the exhaust gases flow from the engine and through the turbine housing, causing the turbine wheel and shaft to rotate. The gases are dis- charged into the atmosphere after passing through the tur- bine housing. As mentioned, the compressor wheel, which is mounted on the opposite end of the turbine wheel shaft, rotates with the turbine wheel. The compressor wheel draws in fresh air, compresses it, and delivers high-pressure air to the engine cylinders. During operation, the turbocharger responds to the engine load demands by reacting to the flow of the exhaust gases. As the engine power output increases or decreases, the turbocharger delivers the required amount of air under all conditions. Under normal atmospheric conditions, air is drawn into a naturally aspirated engine at a maximum pressure of 14.7 psi at sea level. Turbo boost is the term used to describe the positive pressure increase created by a turbocharger. For example, 10 psi of boost means the air is being fed into the engine at 24.7 psi (14.7 psi of atmo- spheric pressure plus 10 pounds of boost). Hoses and clamps To turbocharger Crossover pipe To intake manifold Hoses and clamps A B Turbocharger Charge air cooler Figure 13-29. Turbocharger piping arrangements. A—The location of the crossover pipe or tube on older designs. B—On most newer engines, turbocharged air is routed through a charge air cooler. (Mack Truck David Gaylor/Shutterstock.com) Engine cylinder Charge air cooler Compressor Ambient air inlet Engine exhaust gas flow Compressed airflow Turbine Ambient air inlet Compressor wheel Compressed air discharge Exhaust gas inlet Exhaust gas discharge Turbine wheel Turbine exhaust gas outlet Figure 13-30. The flow of exhaust gases and combustion air through the turbocharger. (Garrett Group)