Electronic Driver Aids
BMW recognizes that the 750i and 750Li are much more likely to be driven by people who don't want-or even understand-the adjustability of the M3 and the M5. The M cars give their drivers almost endless combinations of adjustments to various electronically controlled chassis systems-which is great. But give someone enough rope, and he'll probably hang himself. So rather than allow the 7-series driver to choose an unwise combination of chassis settings, BMW gives the driver the choice of five pre-programmed settings, accessed through Dynamic Driving Control (DDC). DDC takes advantage of BMW's Integrated Chassis Management (ICM) system, which uses a Flexray data transmission system that lets up to 16 chassis control units talk to one another. Sounds complicated, but its job is to make life simpler for you, the driver.
The F01's five pre-programmed modes, in order of increasing "sportiness,"are Comfort, Normal, Sport, Sport Plus, or DSC off. The 7-series will start out in whatever mode it was previously left in, as long as that's either Comfort or Normal. Because the higher modes increase fuel consumption (by putting the transmission in sport mode), the 7-series will revert to Normal on re-start.
As you move up through the modes, the DDC will gradually change the function of, among other things, the following systems:
* Electronic Damping Control. This system gives a computer control over the suspension's shock absorbers and can vary the stiffness of each shock absorber continuously and independently of the others. Additionally, it can also vary the shock's tuning in compression and rebound independently. Going to a sportier mode in DDC will stiffen the suspension accordingly.
* Six-speed automatic transmission. The transmission's shift patterns become gradually more aggressive in the higher modes, leading to increased response but decreased fuel economy. Shoving the transmission selector to the "sport" mode (as on other BMW automatics) accomplishes the same thing independently of the DDC mode.* Electronic throttle control: The higher modes quicken up the accelerator pedal mapping for quicker responses. We're not usually a fan of these systems because they don't actually increase power output, just make it more difficult to drive smoothly.
* Dynamic Drive Control (which is optional, as part of the Sport Package). This system, known from other BMWs, uses computer-controlled actuators to stiffen or loosen the anti-roll bars. Stiff anti-roll bars help reduce body roll in corners but contribute to a rough ride; so when the car isn't cornering, the computer can reduce the preload on the bars, smoothing out the ride. Higher levels in the DDC stiffen up body roll earlier.
* Integral Active Steering (also optional as part of the Sport Package). This system takes BMW's Dynamic Steering to a new level. Dynamic Steering gives the computer control of the steering ratio-the amount you need to turn the steering wheel in order to get a certain response from the front wheels. We've used the system in the past and liked that it allows you to park easily (by reducing the steering ratio at low speeds), but have felt the varying ratios hard to get used to. BMW has taken the system to a new level by adding active rear steering - a system that can electrically turn the rear wheels up to 3' in either direction, also altering the steering ratio. Like other such systems, it turns the rear wheels in the opposite direction of the front at parking speeds (impressively reducing the turning radius by almost three feet), and in the same direction at high speeds (increasing vehicle stability, and also increasing rear-seat comfort by changing yaw-angle forces into lateral forces for the passengers back there). It can also supply small corrective forces during slides, reducing the need for stability control to intervene. Not only can the system change the steering angle, but it can also change the steering effort. And as you select higher modes, the system quickens the steering and reduces assist, giving a more sporty feeling. It's probably the most dramatic change through the DDC modes.
* Dynamic Stability Control (DSC). The 7-series' DSC includes a huge amount of sub-functions, including ABS (anti-lock brakes), ASC (stability control, including a separate mode for stabilizing a trailer), CBC (cornering brake control), DBC (Dynamic Brake Control, which recognizes panic situations and helps the driver to effect a full-braking panic stop with less pedal pressure), Brake Fade Compensation, Brake Drying (which applies the brakes slightly in wet conditions to keep the pads dry and thus ready for use), Brake Standby (which applies slight brake pressure in the event of a sudden lift from the gas, moving the brake pads up against the rotor for quicker response in a panic stop), Startoff Assistant (which prevents the 750i from rolling backwards down a hill as you start out), ACC Active Cruise Control (see below), and automatic brake hold (which holds the car at a stop even with the transmission in gear). And last but not least, the DSC system provides electronic rear limited-slip functionality by braking a spinning rear wheel. DSC is engaged in all modes, except the two most aggressive. In Sport Plus, a special DTC mode is engaged, where the threshold of stability control intervention is raised to allow more spirited driving without intervention. Stability control (but not ABS or the electronic diff functionality) is switched off completely in DSC-off mode (which is selected by holding down the DSC button for several seconds).
Unlike in the M cars, none of the DDC modes are adjustable except one: Sport. In iDrive, you have the option of changing each of the chassis systems individually for your own favorite chassis setting. ...next page >>