Technology. BMW 740i, 740 -
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183 n
Adaptive Transmission Control
Automatic Stability Control plus
Traction (ASC+T)/Dynamic Sta-
Rearview mirror with automatic dimmer 188
Tire Pressure Control (RDC) 189
Water and dirt repelling
Overview
Controls and features
Operation, care and maintenance
Owner service procedures
Advanced technology
Technical data
Index
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
184 n
Airbags ATC
Deceleration sensors continuously monitor the physical forces acting upon the vehicle. In a severe frontal collision, the gas generators of the driver's airbag and the front passenger airbag are ignited. However, the passenger-side airbag is only triggered if an additional sensor has recognized that the passenger seat is occupied.
In the event of a severe side impact, the head protection and side airbags in the front and/or rear * are triggered.
The airbags located under the marked covers inflate and unfold in a matter of a few milliseconds. In this process they tear through the rated breaking points of the upholstered covers or press them out.
Because the inflation process must be virtually instantaneous, it is necessarily accompanied by a certain amount of ignition and inflation noise. The gas which the system employs to inflate the airbag is not dangerous, and the associated smoke is quickly dissipated.
The entire process is completed within fractions of a second.
ATC
On vehicles with automatic transmission Adaptive Transmission Control
(ATC) uses a number of factors to calculate the maximally efficient gear. In this process it monitors your personal driving style, the situation in which you are driving, the condition of the road and the traffic conditions.
ATC recognizes your personal driving style from the positions and movements of the gas pedal, declaration when braking and lateral acceleration through curves. Four shift characteristics – from comfort-oriented to performance-oriented – are available for selection by
ATC.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
ATC ASC+T/DSC
* 185 n
In order to take driving conditions into account, ATC registers corners and both uphill and downhill gradients. For example, if you maintain speed through a curve, the transmission does not upshift.
On uphill gradients, it shifts only when the engine speed increases in order to make more efficient use of power reserves. On downhill gradients ATC downshifts when the speed of the vehicles increases causing the driver to step on the brakes.
With respect to road conditions, ATC monitors the friction between the tires and the road. The system responds to slippery road surfaces (snow and ice) by activating the winter program.
Second gear is used when moving away from a standstill, upshifts occur sooner, and on descents downshifting does not occur in spite of the application of brakes. This enables you to
"feel" the road as you drive and produces greater dynamic stability. If the friction between the tires and the road is adequate, the normal system is again activated. The system also leaves the winter program when you shift from drive position "D" to "S," "3" or "2," or if the ASC+T/DSC * is deactivated.
By recognizing traffic conditions, ATC can retain maximum driving comfort.
For instance, the system recognizes stop-and-go traffic and then proceeds only in second gear until it encounters higher starting loads.
Of course the selector lever can still be used to select specific gear ratios. Performance-oriented driving is enabled by shifting from drive position "D" to "S,"
"3" or "2." Positions "3" and "2" each limit upshifts to the next gear. Position
"2" is best for driving on steep mountain slopes with a heavy load.
Precision sensors monitor the number of revolutions of the wheels. When equipped with DSC, they also monitor steering angle, lateral acceleration, brake pressure and the movement of the vehicle around its vertical axis.
If differences in the wheel speeds occur, the system counteracts the danger of wheelspin by reducing torque. If necessary, the system also responds with additional applications of the brakes at the rear wheels.
If the system detects an instability in the vehicle's condition, the braking action can also be directed to the front wheels by the DSC in order to stabilize the vehicle.
You may need some time to become accustomed to this system intervention.
However, it helps provide optimum propulsive force and driving stability.
The braking intervention may be accompanied by a certain degree of noise.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
186 n
Radio reception BMW Active Seat
*
AM provides substantially longer reception ranges than FM. AM broadcast signals, propagated at ground level in the form of surface waves, are also reflected from the ionosphere as atmospheric waves.
Frequency-modulation (FM) provides substantially better sound quality than
AM. However, because FM transmissions rely on line-of-sight broadcast waves, their effective reception range is limited.
Although numerous factors combine to impose inherent limitations on the reception quality available from mobile radios, specially designed systems can be employed to minimize their effects:
With radio stations which broadcast over multiple frequencies, the "Radio
Data System" (RDS) ensures that the frequency with the best reception quality will automatically be selected.
The Diversity Antenna system employs several FM antennas integrated within the rear window to provide three separate sources for receiving broadcast waves. An integral processor automatically selects the antenna with the best
FM reception quality at any given time.
Because the ongoing antenna selection process is completed within milliseconds, it remains inaudible to the radio listener.
The Active Seat is an advanced development in BMW seats. These seats are engineered with orthopedic considerations so that you will be less fatigued during longer trips and sitting for long periods without moving. The seat is no longer a passive link between the road, the running gear, and the driver. Instead, by means of an active modification to the seat's surface, the seat causes weight transfers which are slight and imperceptible. The basic seating position is not changed by this.
In the seat's upholstery, beneath the surface of the seat, there is a cushion of fluid on the left and right. The fluid is slowly circulated back and forth between the cushions by means of a pump.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
BMW Active Seat
*
Safety belt tensioner DSP sound system
* 187 n
This causes a movement of the spinal column which is barely detectable, together with an improvement in the flow of blood to the intervertebral disks and the muscle structure in the area of the spinal column.
The passengers do not suffer as much from muscle tension, back pain in the lumbar region or symptoms of fatigue.
As a result, the Active Seat represents a significant contribution to driving comfort and driving safety.
The safety belt tensioner responds to collisions by tightening the belts to ensure that occupants remain firmly positioned in their seats. A gas-pressure system retracts the buckle assembly to tension the shoulder and lap belts within fractions of a second. This reduces the tendency to slide under the lap belt.
The DSP Professional premium sound system features a special amplifier combined with Digital Sound Processing (DSP) and integrated speakers to surround you with crisp, true-to-life sound reproduction.
The speaker system's subwoofers, woofers, midrange speakers and tweeters furnish you with an impressively fullbodied listening experience. The individual components are oriented so as to produce the aural sensation that you would experience facing the stage in a concert hall. The system also automatically adjusts the bass and treble settings to compensate for changes in volume and vehicle speed.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
188 n
Rearview mirror with automatic dimmer
The semisolid reacts chemically to this electrical current, thus providing infinitely-variable dimming of the mirror
(electrochromic technology).
As a result, it is no longer necessary to dim the mirror manually, and the driver can maintain full concentration on traffic.
The interior rearview mirror with automatic dimming feature reduces glare from following traffic by adapting the intensity of the reflected images to correspond to levels of light registered by the unit's sensors. The mirror reverts to its undimmed setting as soon as the light source disappears. One of these sensors is mounted on the front of the mirror housing and is designed to monitor light levels in the area immediately forward of the vehicle. The second sensor is integrated within the mirror's glass.
The electronic control system operates by comparing the respective levels of luminous intensity in front of and behind the car. The difference provides the basic parameter used to modulate an electrical current and induce chemical changes in a semisolid layer incorporated in the lens.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
Tire Pressure Control (RDC)
*
Near every wheel, there are antennas in the body which receive the signals from all four wheels. A central electronics system evaluates the quadruple signals which it receives and forwards any changes.
The RDC provides an important contribution to driving safety.
The Tire Pressure Control system assumes the task of regular tire pressure checks for you. Tire pressures are monitored at all four wheels, even when the vehicle is moving.
Behind the valve stem in every wheel, there is an electronic chip which is designed for severe-duty applications and long service life. It contains a pressure sensor, a transmitter and a battery. The pressure is measured in extremely short time intervals and then transmitted by a radio signal. If an irregularity is detected, the transmission rate is increased.
189 n
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
190 n
Xenon lamps
*
The xenon lamps light up the side and front areas of the vehicle with significantly more brightness and uniformity than the traditional halogen lamp.
In a xenon lamp, an electric arc replaces the filament in order to generate intense illumination. A gas mixture in a quartz piston with metal vapor is ignited by a high electric voltage. The arc that is generated is then sustained by a lower voltage. When the lamp is turned on there is a brief period of high intensity. Maximum brightness is attained in approx. 15 seconds.
Xenon lamps provide significantly-improved visibility, especially during adverse weather conditions and driving situations (driving at night in heavy rain or through road repair areas where there are no lanemarkers, for instance).
Vehicles with xenon lamps are equipped with automatic-dynamic headlamp range control. As a result, the highway is always optimally lighted, regardless of load conditions, and drivers in oncoming traffic are not blinded.
Xenon lamps make a significant contribution to highway safety since other highway users, bicyclists and motorcyclists in the right lane, and pedestrians are more easily detected.
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
Water and dirt repellent windshield
*
Additional benefits:
> Clear vision in adverse weather conditions, resulting in enhanced driving safety
> Less glare when driving in the rain at night.
With this windshield (not released at this time), a specially-smoothed surface causes water drops to bead up and run off, thus carrying particles of dirt with them.
Traditional windshields, even when they are in new condition, have a microscopically "rough" surface (1). The surface of the water and dirt repelling windshield is smoothed with a clear transparent fluid.
Depending on the cleanliness of the windshield, the water beads up and runs off at approx. 40 mph (60 km/h) as a result of the air flow (2). The coating has no negative effect on vision through the windshield because it is completely transparent.
191 n
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG
192 n
Online Edition for Part-No. 01 41 9 791 187 - © 12/98 BMW AG

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