I know that a lot of drivers (especially men ), never read an owners manual. But the MB owners manual for our C63s does contain a number of non-highlighted but important text items that MIGHT explain why sometimes the car does not do what we think we have asked it to do.

A good example is on page 135 in the "Kickdown" section. "Kickdown" of course is the MB terminology for an automatic downshift of the transmission by the ECU. A kickdown normally occurs when you floor the gas pedal on U.S. cars or when you press the gas pedal "beyond the (programmed) pressure point". The purpose of course is to get the tranny into a low enough gear that the engine rpm becomes high enough to make decent power.

The important text in this "kickdown" section says: "During kickdown, you cannot change gear using the steering wheel paddle shifters or the selector lever". In other words, once the kickdown process has been started automatically by the computer, any human attempt to control the gear manually is prevented. This can create unexpected outcomes.

For example, you are driving a winding road and have slowed for a corner. Now you hit the gas, without actually flooring it, and then trigger an upshift manual with the right paddle.

On the U.S. version of the car, where only a full throttle pedal position will trigger a downshift, no problem. Kickdown has not been activated because you did not floor the gas pedal.

On the Canadian spec car, the results are different and the outcomes are ambiguous. On the Canadian spec car, a partial pedal push will trigger a downshift. So, if you press the pedal to a sufficient degree, the computer will call for a downshift, and will presumably disregard your paddle instruction to upshift. So the first thing that happens is your tranny shifts down. But any follow-on outcomes are ambiguous, since the text says that your paddle or shift lever instructions will not be honored. This raises a few questions:

- For how LONG will your paddle or shift lever instruction be ineffective? (Assuming you do not react swiftly to the automated downshift and stop pulling the paddle or the lever) Until you let go the paddle? For a few seconds? Or?

- Will the simultaneous receipt of 2 contradictory instructions by the computer (the automated kickdown instruction and the human manual paddle or lever movement) be "gracefully resolved" by good code in the computer, or will the computer temporarily "pause" or reset itself? If it pauses or resets, what happens in the physical reality while it "is confused"? Does the tranny stay in "kickdown" or not? Does it matter what you do with the paddle? (i.e. keep holding it or let it go)

- What happens if you now decrease pressure on the gas pedal, signaling an automated end to the kickdown, but keep keep your fingers on the paddle, will the car now trigger an upshift?

These are the kinds of questions the owners manual does not address, because if it did, it'd be a zillion pages long. They are also the kinds of questions that could explain why an enthusiastic C63 driver might also experience some weird tranny or dash display behavior when enjoying a winding road, or even more likely, a winding and hilly road, even while he/she thinks all he/she is doing is enjoying a spirited drive, and iswondering why the tranny and car are acting strangely.

They are also the kind of questions that the car's computer programming professional must think of, and handle, in his/her ECM coding, and the more complicated the car is, the more such subtle questions he/she must anticipate. On a low production volume vehicle like the C63, he/she might not have anticipated all the possible questions.

But if you read the manual, you can spot such sections of text, and try to imagine what might happen if an unanticipated combination occurs, and not be shocked when it happens . . . .

Jim G

 

Took me a while to understand what happens in manual mode if you want to downshift more than one gear.
I found information that you should keep the downshift paddle pulled, but when I tried it, it seemed to do a multi gear downshift in one shot, so I wondered if there is a way to know if the downshift doesn't go down Too Many gears.

Now I believe that it calculates and takes you to the furthest gear down that keeps you under redline. But I have not seen this in writing, so I am not inclined to try it again.
Also, I have seen no in between. It's either one or all the way down.

I think that this type of question can be successfully asked in the Lounge, during he monthly tech talk with AMG.

 

Also, in any drive mode but M, if you just tap the accelerator quickly with your foot, it will drop down a gear (maybe 2).

 

It is my experience, in a Canadian car, when you floor the throttle the transmission will shift to the lowest gear possible that is acceptable to the shift program. It assumes you are serious and gives you all its got and gets you into the serious part of the rev range. The same thing if you hold the downshift paddle down and are serious with the throttle position. The car will shift down to the lowest acceptable gear possible.

 

It's the strangest thing - when I floor it, my car responds by going really fast.

 

I read that too when I got my car and then promptly forgot it.
I don't drive in M all that often but as I recall shifting up and down is all up to me and the rev limiter.
The rest of the time I just shift away and if do a bad thing I rely on the technology to sort it out and don't worry all that much about it.

 

I use this literally ALL THE TIME...Just blip the throttle and BOOM, auto-downshift. Especially useful if you are just in regular driving situations(C or S) and are preparing to pass someone, instead of pulling out to pass and then letting it find its own gearing I simply blip the throttle when I'm ready to pull out, it auto-downshifts and I'm good to go.

Also, as far as "passing mode"(even though it should be called impromptu rolling street race mode) the way it works is instead of YOU manually downshifting to find the right gear for peak performance, by pulling back on the downshift paddle(or by pulling​ the gear shift left) for about 1.5sec the ECU decides if you need to be 1,2 even 3 gears down for you. I have found the best way to work this is to pull back on the paddle a fraction of a second BEFORE you mat the throttle...When you get your timing down you will find it to be an almost VIOLENT rolling launch.....And this auto-downshift process works in ALL modes, C-S-M all work and also all levels of traction control...Word of WARNING though, if you are at a lower speed(say 35mph or less) and have the ESC in the OFF setting----when the auto-downshift occurs under full throttle it WILL BREAK THE BACK END **COMPLETELY** loose and make you sweat like Hell!!!!

 

Interestingly, from my reading of numerous C63 road tests by car magazines, none of the test drivers appears to have discovered this. Instead, they all tried to pull the downshift paddle multiple times manually to go down "x" gears, and complained about the fact that the tranny would not shift down more than one gear at a time! I guess those testers are not as smart as their clever, attention getting writing styles like to imply.

Jim G

 

i remember when Top Gear did the comparo with the C63, M3 and S4 that Clarkson could ALWAYS get the Merc to break loose in a corner by downshifting and blipping....I would be willing to bet 10:1 odds that what he was actually doing was the "hold paddle" auto-downshift to get the drifts started....Because you are right, MULTIPLE other reviewers complained about the downshift speed in the tranny and also that it only recognized/took action on input for 1 down gear at a time(as in pull back x2 and even though the time to change is still just as slow at the end of that time you are 2 gears down, but in ours if you pull x2 at the end of the downshift time you are only 1 gear down and have to downshift again)....When you get used to and get the timing down on the auto-downshift you will be amazed at how effective it is and also how much faster your car is during full throttle from part throttle rolling situations.