SAguirre

1) You need to remember that even when the ESP is off on Mercedes cars the ESP still turns on (especially if you are hitting the brakes), but it lets you skid a little more when you have it off. The only way to truly disable the ESP is to set the car to Dino. Mode. Even with the ESP, ABS and 4-ETS deactivated, the 4-matic I have has a real hard time breaking loose. Also, this is hard to gage, because even when I simply turn the ESP off button the traction control on the 4-matic immediately turns on and stops the spin out.


2) Where did you get this information about the Mercedes AWD? It is quite wrong. Mercedes Benz 4-Matics do send only 40% of the torque to the front wheels and 60% to the rear, but this is hardly much of a difference. AWD does provide power to the 4 wheels at the same time. This is a FACT in both my Mercedes and my Audi.. The difference is that the 4-ETS that is part of the 4-matic system has open differentials and uses the brakes to stop the wheel that is spinning out. When the wheel that is spinning out is stopped/slowed down, the power then gets transferred to the rest of the wheels through the open differentials. This system on the 4-matic uses some of the sensors that the ESP uses, but it is not the same thing. Like I said, the ESP stops yawl. The Traction control or 4-ETS on a 4-matic stops excessive wheel spin. My old 1986 4000 Quattro was AWD all the time with a true 25% to each wheel distribution. However, it was still possible to spin out if one wheel lost grip, with the differentials locked (all 3) then the car was a 4X4 and did not allow only one wheel to spin, this is what made turning hard. The 4-matic system knows your speed and steering angle and knows how much speed differential should be between each wheel. This gives you the lack of slip of a 4X4 yet lets you turn on a dime because the differentials are still open.

3) Of course this is true and I think that we have been in agreement here all along. The only reason that the ESP still works (better than any other system) on ice is that it still can apply the brake on just one wheel. This can give you just enough drag to kick the car around the way you want it to go. But this is why if you have all wheels on a skid due to a downshift on a 4-matic, the esp is already fighting a worse scenario.

4) Please refer to #2 above. Mercedes 4-Matics along with Subaru, BMW, and Audi send power to all 4 wheels at the same time all the time. The difference is that smart AWD can also direct power to just one wheel. A 4-Matic system can even send power from right to left as well as front to back. Not to mention that one wheel can get up to 70% of the torque for traction. 4x4 simply locks everything up and only lets 25% of the torque to go to each wheel.

5) I think that I used the wrong term with locking up. But you know as well as I do that if you need to stop in a straight line, brakes usually have pretty much the exact same stopping power in the rear axel this means that even if they do lock, they should lock at about the same time and make you skid in a straight line. Like I said before, when you downshift, and you are not touching the brakes, the rear wheels can brake unevenly and guarantee skid and a fishtail where as if you just locked the rear wheels at the same time it would take longer to fishtail after you start to skid. This is why the ABS would work at making sure that the wheels on each side do the same amount of work (skidding or not). This is why I want to say once again that even if you downshifted rather severely (in stupidity) and the wheels started to skid unevenly: a 4_matic could break loose all 4 wheels and really get you going out of control. The ESP starts working only after your car wobbled and since you are NOT accelerating the 4-ETS is not there to help. The only thing left to do is what you mentioned that they teach a driving school which is over and under steer correction.

I think that you might not be too familiar with 4-Matics. They are a truly wonderful system in adverse winter conditions. I don’t know if you ever saw the video I posted over a year ago of me making doughnuts in my E class. I had it under steering and over steering while maintaining control at all times. Snow was flying everywhere and the car had all electronic driving aides turned off. If I had them on, the throttle would have been cut and the ESP brings the car to a halt (in other words, NO FUN).

Another reason why AWD has become miles better than 4x4 for snow/ice driving is that the ABS had to be deactivated when driving with locked differentials. My Audi S6 can send power from the center differential in forms other than it’s standard 50/50% with the ABS on, but the second I lock the rear differential the ABS OFF light turns on on the dash. This is not the best thing to deactivate sometimes (unless you want to play around).

I know that we have gone on a tangent and we are now splitting hairs, but it is nice to type a bit sometimes. The best advice that I can ever give someone when they start driving in snow (aside from good snow tires) is to only do one input at once. When coming to a turn, do all your stopping (if no one is behind you) before you initiate the turn, maintain the speed while turning and then only start accelerating once you are done with turning. You don’t always have to do this, but it sure helps at the start. Also, take you car out and test it when the first snow storm comes.

Take care,

Steve

revstriker

Steve, it's been an interesting discussion, and I do agree with your advice quoted above. As for AWD, my knowledge of this might be older than yours, and I admit, not specific to the vehicles you mentioned. However, in AWD vehicles of the past, there was still only two wheels receiving power at any one time. The power was split between the front and the rear, but only one of each would receive power. That power would then be given to the left or the right wheel, but not split between them. If all 4 wheels received power, you would have some issues when turning corners as one wheel would need to turn at a faster rate than another. Anyway, as I said, my knowledge of this is not specific to any one type of car, and it would not surprise me to find that technology has advanced to the point of controlling this better.

SAguirre

I must say that is is nice to be able to have a discussion without personal insults or stupidity.

The system of AWD that you described was quite prevalent in domestic cars and were very hard to handle sometimes because you never knew when the power was going to be transferred from one axel to the other. This let you start skidding and then you would feel a jolt of power to the front/rear wheels and you sometimes still ended up stuck.

Audi Quattros have been wonderful since the late 1970's and the 4-Matic system of 1998 and newer cars is exceptional. Even on an E500 4-Matic, you will have a hard time breaking wheels loose if you accelerate hard and turn at the same time. The grip and power distribution is wonderful.

Talk to you in other threads!

Steve

CE750

On of the best by-products of debating with Rev.. and I'm not sure if it's cause he's mod either... as other "mods" hold nothing back when they disagree with members.. he's just a nice guy, even if he's wrong about most everything

SAguirre

Well, he is from Texas and his signature has tanks on it. I thought I should be very nice and careful, just in case.

Steve

revstriker

Gee thanks!

And by the way, I'm actually "right" about most everything....

revstriker

Well, I'm not actually "from" Texas, I just happen to be living here at the moment. I'm actually from Boston.

And yes, the Tanks are something else I used to drive a lot, but I'm not alone. CE750 is an old "tanker" as well.

sl561

"I personally only downshift in city driving when I might have passed someone aggressively and then I don't want them to see that I had to immediately put on the brakes ahead of them."

This made me chuckle. I'm so happy to learn that I'm not the only one who has done this. ;-)

DWP

Slowing with the transmission is also a useful technique when you're over the speed limit and you spot the motor cop takin' pictures from behind the shrubbery. It may be too late to avoid being painted by the radar/laser, but if you slow down with the transmission instead of the brakes, you at least avoid the admission of guilt from flashing your brake lights.

sl561

Oh yes. I've done that too.