Chapter 13 Exhaust Systems 301 Copyright Goodheart-Willcox Co., Inc. Turbocharger damage can also be caused by oil lag. Oil lag is a lack of lubrication that occurs when oil pres- sure is not sufficient to deliver oil to the turbocharger bear- ings. Before running the engine up to high rpm, operate it at low speeds for at least 30 seconds after initial start-up to allow the oil flow to become established. Additional time should be allowed when the outside temperature is below freezing (32°F or 0°C). After replacing a turbocharger, or after an engine has been unused or stored for a significant period of time, there can be a considerable lag after the engine is started. Charge Air Coolers Although the turbocharger improves volumetric effi- ciency, it also increases the temperature of the intake air. This increase in temperature is due to the fact that the tur- bocharger compresses the air. The increase in temperature is directly proportional to the amount of air pressure pro- duced. To help counteract this temperature increase, a charge air cooler (CAC) is used. Figure 13-35. Removing a turbocharger. A—Loosening the clamp. B—Disconnecting the drain tube. C—Removing the drain line. D—Removing the fasteners that secure the turbocharger. (Cummins Engine Co., Inc.) A C B D Figure 13-36. Always prime the turbocharger with oil before engine start-up. Starting an engine without prelubricating the turbocharger will drastically shorten the turbo’s life or even destroy it. (Mack Trucks, Inc.)