Physical principle and pressure pattern
WARNING: This page does not describe the selected car, but rather 45 other vehicles, including the 2016 BMW M5, 2016 BMW 550i xDrive, 2016 BMW 550i, 2016 BMW 535i xDrive, and 2016 BMW 535i. However, it is still accessible from the selected car via links, so may be relevant.
The physical principle is based on the ideal gas law:
Pressure and temperature have a direct proportional relationship when quantity and volume remain constant.
The NVLD uses this physical principle to identify leaks in the fuel evaporation system.
This means that a vacuum forms when the temperature in the fuel tank drops. The NVLD uses a temperature sensor to measure the temperature. The NVLD uses the diaphragm-operated pressure switch to determine the vacuum. This diaphragm switches the pressure switch at a certain vacuum/ambient pressure combination.
The following graphic demonstrates the temperature profile and pressure pattern both when there is a leak in the fuel tank and when there is no leak.
| Index | Explanation |
|---|---|
| A | Pressure pattern without leak |
| B | Pressure pattern with leak |
| 1 | Pressure |
| 2 | Temperature |