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Why would M-B include a downshifting function if it were possible to inflict excessive wear or damage on the car by using it? In fact, if you ever use the speed control on this car, IT downshifts! The M-B "electric foot" is more than just a throttle control (as found on most cars). If you've set the speed and the car finds you accelerating down a steep hill - it downshifts! Try it!
My 2000 E430 operator's manual includes six pages of transmission operation instructions. The only thing it warns against is coasting for a long time in Neutral. THAT will void your warranty. This section also describes the elaborate protections for the engine and transmission even if you do command a shift.
Downshifting for performance and upshifting for economy are well-established automobile operating techniques. The manual warnings have to do with over-riding the protections of ABS and ESP - not for wear reasons.
Check with those knowledgable (??)folks at your M-B dealer, and I'd bet they'd tell you that the system was designed for this. The "strain" on the drivetrain should be no greater than a quick acceleration followed by a quick lift off the gas pedal.
IMOH, cars in this class are meant to be driven, not babied. In an E320, there should be no problem since the same transmission shows up in the E430, E500, and probably other, bigger, heavier MB's, too.
Perhaps I'll eventually regret it, but I use the touch-shift function all the time.
First, for EPN2 - -
I'm astounded that you can buy a BMW clutch for $1000. And, BTW, it's the flywheel, the pressure plate, the clutch disk, throw-out bearing and the actuating mechanism that are at risk from clutch abuse. The clutch was the first part they picked up when they started building the engine/transmission sandwich outside car. I'd bet clutch-replacement labor alone is $1000-plus. No car manufacturer I'm familiar with will do warranty repairs for their manual-transmission-clutch-based cars, and you can bet it's for a reason. My son's BMW (which he bought used) has already eaten a clutch in it's first 50k miles. And, it is more than $1000 to fix it, fer. sure. Automatic transmissions have fully lubricated (and thus cooled) band and clutch actuation and linkage, and also have the "cushion" of the torque converter to mitigate the mechanical abuse arising from disagreement between transmission input and output RPM. Moreover, the M-B tranny is a 5-speed. This means that the gear ratios (and thus the RPM discontinuities) are smaller gear-to-gear, further reducing mechanical stress on the system. When you downshift an M-B transmission, there is really very little exciting happening, e.g. passenger heading for the windshield, air-bag deployment, or other signs that the system would rather you didn't downshift.
I said that M-B's are "SUPPOSED to have mecanical robustness that will last forever if properly maintained". Sadly, this doesn't square with my experience, and the scary part is that most of my car's recurring maladies have little to do with mechanical issues. In terms of thwarting a computer's algorithms - the computer isn't looking out my windshield and I reserve the right to override what the computer is thinking to adjust for conditions I see that the "computer" can't. That doesn't mean that I "downshift(ing) away like it was a sports car like Mazda Miata" as you imply. Rather, that the function is there to be used as the driver sees fit and one should not shy away from using it for fear that the drivetrain won't take it. On "fighting the algortihms in the computer": some of the "software" in this car's computer bears scary kinship with a Microsoft Beta release. At any rate, M-B gave me the device to override the car's "algorithms" - - the "+/- gate" in the D position of the transmission - right at my elbow. This is much easier and more direct than that silly zig-zag shift-gate system that was part of the older M-B designs (and the current Jaguars, for example). In any event, the shifting patterns described in the owner's manual suggest that it's far more difficult to abuse the tranny (even if you are determined to do so), compared to the havoc a ham-fisted manual transmission driver can wreak. BTW, my 2000 M-B E430W4 doesn't weigh 3600 lbs. It's more like 3944 lbs and to that you need to add a full tank of gas (127#), a driver and 4 Pax (using the FAA bogey for passenger weight of 170# figure 850#) - some small packages in the trunk, and you're up to about 5000#. Even then, reasonable downshifting is probably OK - at least with an automatic. Okay, so it's not a miata, but it's still fun to drive.
My question for everyone - - do you think a downshift of one gear is more or less abusive than, say, stomping the gas from a dead stop and taking the car right to 100+mph at full engine power while going up through the gears? Remember that these shift points are chosen to maximally bracket the highest torque the engine makes at the next shift point. The performance of the E430 and E55 certainly encourage this, and the E320 is no slouch in the acceleration department, either. The major reason in this case for leaving the shifter in "D" is that at least one review of the car (Car & Driver, as I recall) found the performance of the car to be better left in Drive than with the testers fiddling with the shifter
ESP's primary design objective (according to the owner's manual) is to "counteract over/understeer by applying brakes to the appropriate wheel to create a countervailing vehicle movement." It's watching driver's steering wheel position to determine "driver intent". But, in an obscure reference in the Owner's manual, ESP also has a "torque-reduction feature", which is, in effect, a throttle control. I have experienced the effect of this "feature" personally - - it makes climbing a slippery hill far more difficult than when ESP is disabled.
What we all should get out of this is that it's important to read the manual and understand exactly what ABS, ESP, and BAS (heretofore unmentioned on this website) are thinking about and the corrections they try to make to mitigate what "they" (these systems) see as a problem. (there are parallels in aviation - - understanding exactly what the autopilot is thinking and how it reacts to it's perception of the environment). In severe slippery conditions of the kind we experience in New England (and now, evidently, going on in North Carolina) it is possible that the better course is to disable (that is, turn off) ESP and drive like you were taught before these "autopilot" systems were put into their cars. I have 4-Matic and Blizzak's and still have found occasions where ESP is not helping.
BTW rbrenton88: Oh, I, too, have a charcoal interior. And a Brilliant Silver exterior, CLK wheels, E1, E2, K2a, COMAND, etc. (heh heh). Do you really care? By the way - re: Nappa Leather - - What's a "Nappa"? Is this similar to a "Nauga"?
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