Tire pressure warning system
Technology of the Warnair system

Technical aspects - Information for the technically interested

Short description
DUNLOP TECH Warnair is based on the comparison of the four wheel rotational speed signals to one another as well as to reference data which are made available by the ABS/ESP systems. DUNLOP TECH Warnair detects losses in pressure "indirectly", i.e. due to the changes of rolling circumference resulting from a tire losing air.

Second-generation Warnair (DDWS) uses - beside the evaluation of the rolling circumference - further possibilities for the detection of changes in tire characteristics as they occur when the tire is losing air. For instance, a frequency analysis of the tires is carried out while in transit. This allows for the detection of any losses in tire pressure and other changes in the condition of the tire.

Functional requirements
The system works on the basis of comparing the wheel rotational speed signals of all four wheels to one another as well as with reference data. The rolling circumference and hence the wheel rotational speed of each wheel is influenced not only by the tire pressure but also by the tire dimensions, properties and condition as well as such variables as speed, road surface unevenness, driving style and different slip conditions etc. Information about the inflation pressures of the four tires can be obtained only if these variables are taken into consideration - i.e. either corrected or screened out - and if a representation of normal driving conditions can be used as a reference for comparison.

Operating conditions

  • Under all permissible and customer-relevant conditions (road surface, weather etc.) with ambient temperatures ranging from -40°C up to +60°C.
  • With all permissible load conditions, to include loading with fittings such as luggage racks (e.g. jetbag) and trailer operation.
  •  With all speeds from 15 km/h (model-related deviations are possible) up to the vehicle's maximum speed or 260 km/h, whichever is the lower.
  • With all permissible inflation pressures from 2.0 bar up to 3.5 bar cold inflation pressure. The pressure must correspond with the manufacturer’s specifications as given in the instruction manual.

Calibration (Teach-In)
A manual teach-in procedure - by pressing a switch or a corresponding menu selection in HMI - is required:

  • after changing a tire (e.g. breakdown, replacement, tire change summer/M&S)
  • after a wheel position change (e.g. swapping front axle/rear axle tires)
  • after a tire pressure change occasioned by the driver (e.g. partial load/full load)
  • after repair shop works on the chassis

After the start of calibration DUNLOP TECH Warnair will be fully operational again within a few minutes' journey under normal driving conditions.

System components
The system consists of the following components:

  • Software module integrated in the ABS/ESP control unit
  • Dashboard switch or menu selection in HMI for calibration
  • visual and/or acoustic driver information

Warning behaviour
In its fully calibrated state the system is designed so as to warn of a drop in pressure of a tire of more than 15% below the relative cold inflation pressure.
Display of the affected wheel position is possible. 

Driver operation
The driver is responsible for setting the correct inflation pressures and pressing the switch to start a new calibration when required.

The responsibility for the condition of the tires and their correct pressures remains always with the driver.

Tire pressure warning system





Warnair system

is an integral part

of selected Bosch

ABS and ESP systems.