Robert D. Mitchell
Product Information Manager
NEW ADAPTIVE TRANSMISSION CONTROL IN 1994 BMW 5-SERIES V-8 MODELS IS A MAJOR STEP FORWARD IN AUTOMATIC TRANSMISSION PERFORMANCE
Woodcliff Lake, New Jersey...Effective with September 1993 production, the 5-speed automatic transmission of the BMW 530i Sedan and Touring and 540i Sedan incorporates a new refinement that could be said to revolutionize the way an automatic transmission responds to its driver, to environmental conditions and to the driving situation at hand. It's called Adaptive Transmission Control, or ATC. For some years now, BMW's electronically controlled automatic transmissions have offered the driver several choices of "shift modes," or programs. Typically, an Economy mode, aimed at everyday driving and always engaged when the driver put the selector lever in "D," provides upshifts at relatively low vehicle speeds with an eye to best fuel economy, quietness and smoothness. A Sport mode causes upshifts and downshifts to occur at higher engine speeds, enhancing response. Depending on the BMW model, there has also been either a Manual mode to give the driver full control over shifts, or a Winter mode to help reduce wheelspin when starting up on snow or ice. ATC goes two fascinating steps further by: Increasing the number of modes from three to nine. Making the mode selections automatically. And in case this raises a question of whether driver choice is thereby reduced, let us state going in that it most definitely does not; instead, ATC employs highly sophisticated electronic logic to recognize what is going on with the driver, the environment and traffic, and does a remarkable job of making the transmission respond ideally in view of all that. You could even say that it improves driver choice, in that it relieves the driver of having to think about selecting a mode and frees him or her to concentrate on traffic and the road. At the same time, ATC eliminates some minor operational drawbacks that have been present in automatic transmissions since they first came into use back in the Thirties -- mainly to the irritation of particularly skilled or sensitive drivers. To accomplish these remarkable results, ATC employs the following "recognition" elements, and controls the transmission accordingly: Driver-Type Recognition Environmental Recognition Driving-Situation Recognition. Driver Type Recognition. Utilizing the remarkable capabilities of microprocessors, this logic is able to track how the driver has been "behaving" over the past few seconds. If, for example, the driver has been stepping hard on the accelerator, the logic concludes that he or she is in a sporty mood, and selects and holds either of the two available Sport modes. As with the manually selected Sport mode in other BMW models, this causes upshifts and downshifts to take place at higher engine speeds, and one of these modes will be held for a period of time (generally 5-10 seconds) after the system has made its decision. Likewise, quick accelerator-pedal movements cause selection of one of the Sport modes. If there are no abrupt accelerator movements for a certain length of time, one of two economy-oriented shift modes (similar to the manually selected Economy mode of other BMW models) is selected; upshifts and downshifts take place at lower engine speeds and fuel economy is optimized. In another recognition of accelerator-pedal movements, whenever the driver releases the accelerator quickly and the transmission is in a lower gear (say 1st through 4th), ATC will not allow an upshift. Thus the engine braking of the lower gear remains in effect -- surely a bonus in this situation, when the driver wants to slow down anyway -- and (as smoothly as this transmission shifts) the lack of an unwanted shift is bound to be a subtle plus as well. Environmental Recognition. The logic detects any increase in driving resistance, such as when the car is carrying an above-average load or is climbing or descending a grade; or a decrease in traction, such as on ice or snow. In the former case, it selects one of two available Mountain modes and prevents unwanted upshifts, or even causes a downshift if the driver applies the brakes on a downhill run. In the latter, it selects a Winter mode; moving off from rest, for example, the transmission will select a higher gear rather than 1st. Driving-Situation Recognition. In stop-and-go traffic, the logic detects that throttle openings and road speeds have remained below certain limits for a period of time. The transmission then rules out 1st gear, reducing unwanted "shift activity" that can make this bothersome kind of driving even more so. This is referred to as a Stop-and-Go mode. For driving on a winding road, the logic detects when the car is cornering above a certain "g" level; if the driver releases the accelerator and the transmission is in a lower gear, that gear will be held, eliminating unwanted or awkward downshifts under this circumstance. In addition to ATC, the 5-Series 5-speed automatic does retain a 2-position console mode switch marked "A" and "M." The "A" position denotes Adaptive, with operation as described. In the "M" mode, the driver can select any gear from 1st through 4th manually via the shift lever. So this particular driver choice, which seems the only one ATC might not be able to make effectively, remains to give the BMW driver pure manual operation when desired. Adaptive Transmission Control is a remarkable step forward. In a sense, it makes an automatic transmission as responsive to the driver's wishes as a good manual transmission, yet without requiring any additional manual control. You can't ask for much more than that. BMW believes that it is yet another contribution to making the BMW driver a Better Driver.