# Idle Vibration Reduction of a Diesel Sport Utility Vehicle
## 2 Experimental Analysis  
The paths through which the idling vibration is transmitted were identified prior to the experimental analysis of the dynamic behavior of a diesel SUV during engine idling. The diesel SUV considered in this study possessed a transverse-mounted four-cylinder engine driven by its front wheels; this SUV produced considerable vibrations that were perceivable by the passenger. Generally, the powertrain (i.e., the engine and transmission) of the transverse engine is placed parallel to the driving axis of the front wheels. To identify the transmission paths, automotive parts related to the transmission of vibrations were selected, and the connecting structures of these parts were analyzed in terms of their dynamics. As shown in Figure 1, the main components on the transmission paths from the idling engine that generates vibrations to the floor of the driver's seat are the powertrain, radiator, intercooler, front end module (FEM) carrier, side member, cross member, and the body floor. The \(x\)-, \(y\)-, and \(z\)-axes represent the longitudinal, transverse, and vertical directions of the vehicle, respectively. The vibrations produced by the idling engine are mainly transmitted along two paths from the engine to the body floor, as shown in Figure 2. The first path lies through the mounts of the powertrain, whereas the second path lies through the radiator or intercooler. First, the powertrain mount serves as the path through which the vibration is transmitted sequentially from the powertrain, three mounts, the front side member, and the body floor. The side member structurally supports the powertrain and imparts strength and rigidity to the front body. The powertrain mounts reduce the idling vibrations caused by the explosive force of engine, which are transmitted to the body floor. The powertrain used in this study is supported at three points by an engine mount, a transmission mount, and a roll mount. Herein, the engine and transmission mounts are fixed to the right and left side members, respectively, and the roll mount is fixed to the cross member. The side and cross members are welded and strongly bonded to the body floor. Furthermore, the radiator/intercooler path consists of the powertrain, a radiator/intercooler, an FEM carrier, a side member, and the body floor. The cooling systems, i.e., the radiator and intercooler, which are located at the front of the powertrain, are connected to the engine through the inlet and outlet hoses. The hoses connecting the radiator and the powertrain are made of rubber, and the hoses connecting the intercooler and the powertrain are composed of plastic and rubber. In particular, the radiator and intercooler are mounted on the FEM carrier with rubber bushings. The radiator is connected to the FEM via two upper and two lower bushings, whereas the intercooler is connected to the FEM via one upper and two lower bushings. The FEM carrier is firmly bolted to the front of the side member. When the engine is in an idle state, the dynamic behaviors of the powertrain, radiator, intercooler, and body, which are components of a diesel SUV, were investigated through an ODS analysis. The ODS represents the shape of a structure that has been deformed  
Figure 1: Components of a diesel SUV on the transmission paths of idling vibration. Figure 2: Transmission paths of idle vibration for the diesel SUV. or set into motion by an excitation force, and it is generally used to analyze the shape deformation over time or at a specific frequency. To analyze the vibration of the SUV during engine idling, the dynamic deformation shapes of various vehicle parts at the excitation frequency under idling conditions were obtained through ODS analysis. In this paper, the experimental method for the ODS analysis has been briefly described. Please refer to the concerned study [21] for more details on the ODS analysis and related experimental method.