2007 BMW M6
--> Article summary:
Initially, the M6 is offered exclusively with this unique SMG transmission, which employs Formula 1 racing technology to help drivers extract the M5’s full performance potential. For M6 customers who prefer a conventional manual transmission, a 6-speed will be offered later. This amazing new system does everything a manual transmission can do, plus several things a manual can’t:
This is the first SMG designed and developed right from the start as an SMG; Two BMW M generations and the simpler system offered in regular-production BMWs were created by adding SMG controls to a conventional manual transmission. This has sweeping implications for how the concept operates and what it can do:
- Offers 7 forward gears, which would be awkward for a manual shift lever to manage.
- In high-performance driving, can shift much faster than even an expert driver.
- Can provide automated shifting when desired.
- Offers a wide variety of shift programs in Automated and Sequential modes.
- Engages and disengages the twin-disc clutch, precisely coordinating its action with shifts. There is no clutch pedal.
DRIVELOGIC shift programs, 11 of them. In this respect, the new transmission parallels BMW M’s 6-speed SMG, offered on M3s since 2002. There are two basic shift modes: Sequential (S), in which most shifting is initiated by the driver; and Automated (D, for Drive), in which operation is similar – but by no means identical – to that of a automatic transmission.Within these two modes, there are as before a total of 11 shift programs:
- The gears are positioned in so that the gearsets with the greatest loads (1st, 2nd and 3rd) are closest to the load-carrying bearings. This promotes durability in a transmission that must transmit immense power and is shifted fast and hard.
- To be shifted by a conventional shift lever, this gearset placement would result in an extremely awkward shift pattern. But this was not a problem, because all shifting would be executed the SMG way.
- Even if the shift pattern were manageable, 7 speeds would be difficult for a driver to manage; a 6-speed is the practical limit for a purely manual transmission.
- And yet with a high-revving, high-performance engine, 7 speeds are ideal and desirable, tangibly helping the driver extract such an engine’s full potential.
- The entire internal mechanism – gears, shafts, bearings, shift rods – could be laid out optimally for SMG’s electrohydraulically powered shifting; it is in no way compromised to allow conventional manual shifting.
- The mechanism allows simultaneous actuation of two shift rods at once, which helps the unit achieve lightning-quick shifts. Additionally, the gear synchronizers utilize carbon-fiber cones, which also contribute to the ability to shift so fast.
In S6, the sportiest program of all, minimum shift time is reduced 20% from the existing SMG – already very fast. In everyday driving, shifts are now smoother.As in the existing SMG, gears are shifted electrohydraulically; shifting is controlled by a 16-bit microprocessor that can make up to 12 million calculations per second.Special functions and safeguards. The 7-speed SMG incorporates a number of special functions and safeguards, some familiar and some new:
- Sequential – 6 programs, S1-S6 from “softest and slowest” to “hardest and quickest” shifts; i.e. from most leisurely to sportiest. The driver initiates shifts with either the console shift lever (tip forward for downshifts, rearward for upshifts) or “paddles” on the steering wheel (left paddle for downshifts, right for upshifts).
- Automated – 5 programs, D1-D5 similarly from mildest to sportiest, with the distinction that as the program gets sportier, the speeds at which shifts occur also move upward. Even in this D mode, if the driver manually initiates a shift, the unit switches to S and remains there until D is again selected by the driver.
Launch Control. In S6, the driver can utilize a further SMG capability. Dynamic Stability Control must be de-activated via its console button. Then the driver holds the shift lever forward (as if for a downshift) and presses the accelerator pedal fully down. This raises the engine to 1600 rpm. Ready to go, the driver now releases the shift lever. Engine speed rises immediately to 8000 rpm; the M6 launches with precisely balanced clutch slip and wheelspin for an optimum start. From there, the driver upshifts as desired – most likely at the redline, as maximum performance is the point of the exercise. Thus utilized, Launch Control gives essentially the same standing-start acceleration results as an expert driver. To preclude overheating the clutch, the system requires several minutes between Launch Control starts. Automatic downshift to 1st gear for starting off from rest, whether in D or S mode. If the mode selector is in D, upshifts will then occur automatically; or the driver can initiate the upshifts.Overspeed protection. If the driver calls for a downshift (S mode) that would overspeed the engine, the downshift command is ignored.
Slip Control. If a downshift occurs on a slippery road, SMG disengages the clutch for a split second to prevent sudden wheel slip that could de-stabilize the vehicle. Start-off Assistant. When stopped facing uphill, the driver simply holds the brake pedal until ready to start off. Upon release of the brakes, the M5 is ready (for 1 second) to start off without rolling back.
Hill Detection. Depending on road gradient, down- or uphill, the D shift points are modified for optimum gear selection. In S, shift times are shortened so that the engine is always “on point” for best acceleration uphill, or engine braking downhill.
Double-clutching. In D or S mode, DRIVELOGIC coordinates clutch disengagement, shifting, engine speed and clutch engagement to accomplish smooth downshifts – just as a skilled driver would.
2nd-gear start in D1 program: Starting up from rest, the transmission is in 2nd rather than 1st; the clutch engages delicately. Although the traction-control function is also there to prevent it, this reduces the chance of even transitory wheelspin.
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| Transmission:||7-Speed manual |
| Horsepower @ RPM:||500@7750 |
| MPG(Cty):||18 |
| MPG(Hwy):||12 |
| Torque @ RPM:||6100 |
| Displacement:||4999 L |
| Curb Weight:||3909 lbs. |
| 0-60 time:||4.5 sec. |
| Top Speed:||155 mph