007_e350

I've been experimenting with Tranny's C/S modes for a while and on our 6 hr drive yesterday I am leaning towards a few conclusions, I'm posting these so we all can brainstorm this bizarre option

- Torque: C is definitely more torquey than S ... I've come to this conclusion by observing in numerous uphills ... C climbs better, growls more but is sluggish in acceleration [trucks are sluggish too but have enormous torques.. not comparing to trucks just to explain myself ] .. - - What could it be: Though I'm looking for documentation here but its almost like engaging a bigger bulkier flywheel in C & disconnecting the bigger flywheel in S maybe magnetically I dont know - have I gone nuts ? Or maybe richer air-fuel mixture settings in C ?
This should explain why C can roll from 2nd gear - MB engineers aren't stupid: they know the torque can support the roll - but not the sprint where the S mode comes in
- Mpg wise: S gets slightly better gas mileage than C
- Engine Growl: Definitely higher in C
- whatelse..

sosh

S has much more torque. The shift points are set for the highest performance. there are no other changes other than the shift points and starting off in first gear.As for fuel mileage there is really no significant difference between C and S. My take on this is from 3 E Classes I have owned, an 01, 05 and now a 2010.

lkchris

Don't imagine so many mythological differences.

C or "winter" mode simply starts car in 2nd gear from stop instead of 1st and limits engine rpm before upshift. It really is a good idea in slippery conditions and it may provide a little more economy, too, as it will force higher gears.

S permits all transmission function, i.e. 1st gear start and revs to redline before upshifts (if demanded).

This doesn't change engine running at all

sosh

You are absolutely correct. This guy has a vivid imagination and is making a mountain out of something quite simple. By the way the switch used to be labled W and S for winter summer.

007_e350

There has to be more than just starting from 2nd gear -- this could hurt the drivetrain unless something else changes -- which is exactly what I'm tryinto find out

Anyone who's driven a stick would know how a car shakes when you try to roll out in 2nd off a stop - the whole car shakes ... I'm tellin ya there has to be 'some change' associated with this switch (mechanically or chemically i.e..)

I know I'm a psycho

novae500

When i bought mine, the SA said to keep in C for smoother take off, since starts in 2nd gear. But put in S if you want to take off faster at a stop... Leave it in S, but when wife drives, she puts it in C (that is if she remembers too:-) )

Barry45RPM

1st gear in these cars ia a very very low gear, and you're in it only for a nano second. Our 2nd is most peoples 1st.

Basically C eliminates 1st gear & changes the shift points... sad, but true... thats all there is to it.

Clinton Horn

For one thing, you get better hill holding from the lockout position (w or whatever is the new designation). I guess the tranny resists rolling backwards in the higher gear.

I typically set ours up for 2-3-4 in city driving. I don't need the granny gear and the 5th is a waste as it rarely stays for more than a couple of blocks.

Probably wishful thinking but surely 2 shifts saved in every 1/2 mile or so of city driving is a good thing.

I started out with GM power glide
60mph first and whatever she would do in high

Moved on to GM Hydramatic- 3 gears- much better for burning rubber off the old man's tires.

Next came 4 with 1:1 lockup. Very fuel efficient but prone to early failure.

Then 5 speed - I thought it was nice but sort of gilding the lily.

Now 7 speed (8 in Nippon )? Mercy, where will it all end?

adisco93

I have been having this dilemma for a bit as well. My last car was a 6spd - I listened to my engine before shifting the gears except when racing or needing to quickly merge onto a highway. I have been driving in S for quite some time and hated the fact that it seemed like the 1st and 2nd gears just seemed to stretch forever even when i was not trying to race...it was/is really annoying. I just felt like the car never shifted quickly enough.

I have been using C for about 3 or so weeks and it tends not to hold the gears for as long as the S but still stretches it out a bit more than I care for it to- tried the paddle shifters- useless! I think i was getting better mileage with the car in S though. I just need the car to shift a bit quicker......

This is the first automatic car i have ever owned.

220S

Torque is the turning force. That useful torque in a motor is only available over a range of rotational speed, which is measured as rpms.

All the transmission is doing is allowing the motor to use (and reach) certain rpms. If your engine's max torque is say at 7k, then that's when you'll feel the max torque.

All auto transmissions are designed for keeping the rotational speed in a usable area (to move the car) and to be economical; there's no sense in running the motor at 7k all the time, when the usable torque is available over a range of rpms (say, 2k to 7k.) Modern engines have a broad torque range and depending on design can be pretty linear within a given range, and with the peak say at 6k or 7k.

The transmission will only give you max torque if you let it put you into the motor's torque range and the power peak of torque. That's what S mode does. C mode doesn't take advantage of the peak and is for fuel efficiency.

For those complaining about the design of your tranny, it's set up to give you the highest efficiency of torque (power) and economy. That's why they made a 7 speed (overdrive tranny.) It will always put it into the usable torque range depending on speed and resistance. If you're going up a hill, it gives you the best of the torque, etc.. Once the car has less resistance, then the power band isn't needed so much and the car shifts quicker (5 thru 7.) Just let it do its thing (except if you want to always keep the motor in the max usable torque range and manually shift to keep rpms in a specific spot, as in racing.)

007_e350

+1 --- 100% agreed!


220S: can you help us explain why S give better mileage even when shift points are at higher rpms...


My SA told me to keep the car is S as C starts from 2nd gear and can cause 'load' on the engine.. higher load more gas ?? --

Regarding shift points - I think its driver foot sensitive regardless of S or C, whenever i want to downshift I just release the gas a bit and there's the shift regardless of being in S or C & to make it worse, it will adapt to your driving style over a month or two (see posts on resetting trans ECU-they say it makes a difference) ... S is just more responsive @ the same RPM as you'd observe in C ---- anybody knows why ?

220S

Sorry, but your SA is clueless. There is no load from the tranny. This was discussed by the MBUSA staff on the AMG Private Lounge forums. I'll try and find it, but they don't allow cut and pasting (but I'll re-word it and post.)

The tranny is adaptive. You can train it to do anything. Foot sensitive? The throttle is a DBW system.

You will get less gas mileage. Gas mileage is dependent on several factors and keeping the motor spinning is just one. How are you actually measuring this? You cannot do it methodically unless all variables are identical.

Your brain is telling you myths. S is just more responsive at the same rpm as in C? What does that mean? rpm is rpm. And again, it's a DBW ETM.

You can change the mapping on the ETM with a Sprint Booster, but the shift points are changed in the ECU when you select S or C. And you can change those points by making the tranny adapt (adaptive transmission.)

There's a lot of tech info on how a tranny works, etc.. Take a look. But what you are implying with your first post is erroneous.

edit: here's the response from the techs at MBUSA as promised (I'll re-word it since they don't want cut and pasting): There is no load or any clutch wear in the auto tranny because it's the torque converter that does the slipping and so it's simply a fluid shear. In S mode, the tranny gets a lot more clutch activity (shifts a lot more often to keep it in the upper rpm power band both up shifting and down shifting.) Also for longevity, C mode is suggested (less shift activity and shift speeds are slower; basically less wear and tear in C mode) and better gas economy.

007_e350

Now we're talking! I dont know much abt torque converters, will read up on em

question remains on fuel consumption ....

220S

You are not getting better fuel economy in S mode over C mode if all parameters are identical. And that's something you can't empirically know unless you are in a controlled setting. There will always be driving differences, rolling resistance differences, altitude/humidity, etc., in your "out on the street" mileage testing from day to day, week to week.

Take the tech's word for it when they say you'll get better fuel economy in C mode in an ideal setting.

gaazmon

C can't be bad for the car. Before the cars had S / W switch, wouldn't the D gear always start you off on 2nd (like my 94 S420)? only if you dropped it manually to the lowest gear (which was labeled B on my car, idk why) would start you off in 1st. gears would go B, 2, 3, D).

I think even BMWs start off in 2nd. My friend had an 07 530i and the tranny would start off default with sport mode off. you would have to engage it manually.

emilner

To prove C is not bad for the car (as if it is needed, I mean, MB did put it in the car) just look at the 212. Every time you start the car it reverts back to C...

Barry45RPM

...and the owners manual states thet you should keep the trans in "C" only for the first 1,000 miles of ownership for "Break In".

chokaay

This thread has got me intrigued again about C/S modes.

The last time I "experimented" with them (which wasn't very thoroughly), it seemed to get about the same gas mileage for me (around 300-330 mi before the fuel light comes on). However, the ability to accelerate faster in S was very noticeable, and I found the car doesn't seem to shift as often when I'm driving (the car always tends to downshift fairly often when I'm in C, both city and highway driving... maybe because I tend to have a heavy foot).

I'll run more extended tests and see which mode is better for my driving style. I'm tending to think that the less frequent shifting of S might be better for the tranny... but the lower RPM's and minimal mpg savings (every drop helps) might be better for the engine (and my pocket book... however few cents it is).

gaazmon

i started experimenting to yesterday and today and noticed the same thing. the car feels much heavier on C. when in reverse, if i let off the brake the car will not even move on it's own. also, it shifts sooner in C and that creates a problem in my community since it is all hills and turns. so i'm just leaving it in S again. the only problem with S is when i hit traffic, the computer goes haywire and at low speeds (5 mph) starts to jerk and make this loud noise. i don't know wtf that is

chokaay

Whatever it is... that doesn't sound good...

I'm going to leave my car on S for a few tanks of gas and calculate the mileage compared to C. I noticed that the car accelerates effortlessly now (doesn't need to downshift, and no struggling or hesitation when I floor it), and easily passes cars when I just lightly touch the accelerator. I also do notice the engine braking has increased though, whereas when I used to be able to let off the gas and coast for a quarter mile before my speed even started to slow down, now it seems like the needle will begin to fall almost immediately (although the fall starts off slow and very gradually picks up). Give-and-take I guess...