The accelerometer can be mounted on any solid surface in the car that's within reach of the wiring harness (about 20 feet of cable is supplied). The location needs to be free from harsh road and engine vibrations. DynoLab recommends using the trunk floor as a mounting location and we did just that, picking the part of the floor that ramps up from on top of the fuel tank to where the spare tire is stored. As shown here, we removed the accelerometer from the mounting bracket before installing the bracket. With the bracket in the desired position, mark the four holes with a marker and drill the hole locations in the floor, making sure you don't drill into the gas tank. Mount the bracket with sheetmetal screws. Although the accelerometer is essentially watertight, DynoLab recommends making sure the mounting location will remain as dry as possible.