Multiple Restraints System - Overview: Overview BMW X5 E53 рестайлинг

MULTIPLE RESTRAINT SYSTEM (MRS III) INTRODUCTION

The X5 is equipped with the Multiple Restraint System (MRS III) which employs the use of "SMART" technology. Smart technology refers to the control module's programming which allows for the deployment of the airbags, in stages, depending on the severity of the impact. Two stage airbags are used for both the driver and front passenger which allows for a softer cushioning effect when the bags are triggered at lighter impacts.

The MRS III system is installed in E38/E39 and E46 Sedan vehicles as of 3/99 production and in E46 Coupes as of 6/99 production.

MRS III control modules are manufactured by either Bosch or Temic. While the functional operation of both modules are the same. The control modules are not interchangeable from a replacement standpoint.

In addition to the use of two stage airbags for the driver and passenger, the following features are also included in the MRS III system

1. The MRS III control module is linked to the K-Bus for coding and diagnosis.
2. The MRS III includes a fuel pump cut off feature in the event of an airbag deployment.
3. Inert gas generators are now used for all air bags and seat belt tensioners.
4. The inert gas is a mixture of hydrogen (13.5%) and oxygen (86.5%).

MRS III OPERATION

As with previous systems, the triggering thresholds are programmed in the MRS III control module. These thresholds are determined by BMW through crash and vehicle testing during the design and development of the vehicle. These thresholds will vary depending on the vehicle size and design.

There are several different thresholds for airbag and safety restraint deployment including

1. Belt pre-tensioner threshold for activation of the seat belt tensioners.
2. Airbag threshold #1 - the first level of activation for the two stage front airbags, always deployed first when the front triggering threshold is reached.
3. Airbag threshold #2 - the second level of the two stage front airbags, can be deployed simultaneously or after a time delay, depending on the severity of the impact.
4. Rear crash threshold - for activation of the seatbelt tensioners with a rear impact.
5. Battery safety terminal threshold - for activation of the BST with airbag deployment.
6. Side airbag/ITS threshold - for deployment of the side and thorax airbags.