raywong@hkstar.

Besides cutting fuel during wheel slip, what does it really do?
Does it act like a smart LSD? How does it behave when entering/existing a turn? Do our cars have G sensors?

PC Valkyrie

ESP stands for Electronic Stability Program. It is an umbrella term which combines 2 features:

1) Traction Control (what Mercedes calls ASR)
2) Stability Control

Traction Control (ASR) is exactly what the names implies. It will brake individual wheels or cut engine power if there is excessive wheelspin in either drive wheel in low traction conditions when you accelerate (from a stop or while in motion). In a way, it can act like a pseudo limited slip differential, but it is reactive in nature (a wheel has to start slipping before the brake activates to stop that excessive spinning). When accelerating out of a corner, the inside wheel often will "slip". The benz should detect that slip and brake that wheel slightly. The open differential should then transfer more power to the outside drive wheel which has more traction. So in a way, it does help in a turn like a LSD would. At least this is what is claimed in the promotional materials of the C55.

Stability control comes on when the car senses that you are not traveling in the direction of your intended path. It measures your steering input, speed, and what direction the car is actually heading in. If it senses understeer or oversteer, it will brake the appropriate wheel or cut engine power to bring the car back in line with where you want to go.

When you push that ESP off button, what happens is the ASR (traction control) is disabled. You can start spinning your wheels in the snow when you accelerate. However, the stability control is not completely disabled (I think it just intervenes at a much higher threshold).

raywong@hkstar.

Does ESP apply braking on all 4 wheels?

PC Valkyrie

It will apply brake power to whichever drive wheel to prevent excessive wheel spin (traction control) or to any one of the wheels to correct under- or oversteer (stability control). I don't think there is any scenario where ESP will apply brakes to all 4 wheels at once.

From your way of asking, I don't think you really understand what I'm talking about.

Expat

Gives your heart a workout by cutting your acceleration when you pull out in front of an 18 wheeler!
Personally I'd prefer the reduced acceleration you get when one or both of the drive wheels is spinning v's the "dead in the water" MB aproach.

clkcadet

i hate that!!!!
not to mention i hate the fact that a burnout is near non existent, i dont know about you V8 guys, but my 320's tires wont budge for more than a fraction of a second

<----needs tips lol

Zeppelin

That's called " lack of power". A C32 will vaporize the rear tires with ESP off.

raywong@hkstar.

So ESP has control on all 4 wheels? My car oversteers a little when entering a coner. The tire is still sticking the rear end just step out a little. Maybe the ESP could tell from the rapid deceleration and steering input that I am entering the conner, and it apply more braking in the inside rear wheels to help tuck in the car.
During the middle of a turn, if ESP is smart enough it should continue to apply some braking on the inside rear wheel to tighten the turn.
When exiting a turn, the ESP should let go of the brake so the car can go straight again.

Expat

As far as I can tell ESP is way dumber than that, I pull out at a junction one of the drive wheels starts slipping, rather than transfer the power to the wheel with grip it cuts the fuel so that the car almost stops, I get to watch the traffic head towards me at high speed then the car regains grip and takes off like a rocket.........

raywong@hkstar.

The ESP is getting imformation only from the steering angle and wheel speed sensors? No lateral and longitudinal G sensors? Even my Mitsubishi has them long time ago. MB is so low tech!

PC Valkyrie

From the mercedes international website. The following describes the stability control portion of the ESP:

"The heart of the system is a yaw-rate sensor from the aeronautics sector. This unit continuously monitors the movement of the vehicle about its vertical axis and compares the actual value with the target value calculated on the basis of the driver's steering input and the vehicle speed. The moment the car deviates from this ideal line, ESP® intervenes to counteract any incipient tendency to skid by applying a precisely metered braking force to one or more wheels. ESP® combines the functions of ABS and ASR and complements them with directional stability assistance."

Our cars actually have a yaw-rate sensor, a steering angle sensor, a lateral acceleration sensor, and wheel speed sensor.

For the traction control (ASR) portion of the ESP, the international website describes it like this:

"As soon as ESP® identifies a critical driving situation – e.g. through sudden wheelspin – it intervenes by applying specific brake pressure to one or more wheels, as required. If necessary, the engine torque is also adjusted automatically."

So in other words, it will first apply the necessary brake pressure. If you're a "floor it" type of person and not recognize you are losing traction and overpower the braking force, then the power will be cut.

It amazes me sometimes that some people here don't realize the fine points of driving a relatively powerful car like our C32 or C55's. You can't expect to just stomp on the gas and fly. If you don't have the traction, you are going to spin your tires without ESP. In the past, people have to "feather" the throttle to really know how to handle the power of cars like ours.

Jakpro1

Don't forget, when ESP cannot "stop wheelspin" on both tires, it orders the throttle body to close until traction is acheived, thus the near impossible burnout with it on.

Zeppelin

You must have the only C32 in the world that has oversteer in any way other than applying throttle. These things understeer like pigs no matter how the suspension is set-up. Oversteer can only be had with the gas pedal.

raywong@hkstar.

I get oversteers everytime I enter this local hiway turn. Here's what happens...

1) Brake hard from 230kph to 140kph before the turn.
2) Start to turn the steering slowly to enter the turn, while easing off the brake.
3) Car starts to oversteers, the tire's are not squealing, the rear end just steps out like turning a rudder.

What cause the oversteers? Maybe my funny suspension, the high weight transfer, the sloppy rear linkage, the ESP doing its wonder...?

Zeppelin

I think you should be getting back on the gas before the turn to settle the car down. Lifting off the brake pedal no matter how gently will upset any car in a turn. I can tell you that in my car with ESP on you can slam the steering wheel from side to side as fast as you want at any speed and the car is perfectly stable. That's why this car makes a terrible learning tool for a track car. You can drive it around a road course all day long and not learn a thing about driving.

m3_eater

That's trail-braking oversteer. Consider yourself lucky that our car will even do it. If you downshifted prior to the corner, you could then smoothly apply the throttle and the result would be traction regained and a flattening towards neutral. On the right curve, you might then be able to dial in power-on oversteer on the exit (for fun, not best speed). Problem is, the C32 is bad on the understeer - it really does push an awful lot.

Expat

Is this true for all C32s & C55s or did it get added/updated in a specific year as the ESP my 2002 C32 doesn't seem to be acting that intelligently?

PC Valkyrie

The basic principle of ESP is the same for all Merecedes cars. I had a 2002 C240 and ESP worked great (best way to test it is in the snow). The stability control promptly corrected understeer or oversteer. The traction control braked the spinning wheels and/or cut engine power if you kept your foot on the pedal.

For the C55, the promotional materials imply that ESP was tuned for more aggressive driving (which may mean different thresholds of intervention), but the actual way ESP works should be the same. Don't know if the C32 had more "aggressive" ESP tuning.

Remember one thing: if you're going way too fast around a curve, no electronic stability control can save you if you're sliding too quickly. It takes some finesse to drive these cars at the limit. If you just stomp the gas when you have limited traction, the power will be cut (and then some of you will get upset and blame the car).

PC Valkyrie

Here is some material of about the revised chassis and ESP setup of the C55:

"More fun behind the wheel and improved dynamic handling without any major sacrifice of comfort - these were the goals laid down for the chassis development of the new C 55 AMG. The responsible engineers and technicians at Mercedes-AMG GmbH focused on three areas in their developmental work: chassis tuning, dynamicdrive control system and wheel-tyre combinations. All components and systems had to be adapted to the new V8 engine in order to achieve extra sportiness.

The new AMG sport chassis makes a significant contribution to boosting the dynamic handling. Springs with a 20-percent higher rigidity, harder gas shock absorbers with degressive characteristics and a bigger stabilizer on the rear axle (only in the C 55 AMG estate) not only make the most of out of the road but also reduce the body roll that happens when a car drives rapidly through a curve and the roll angle in alternating curves. The elastokinematics were reworked on both axles: Both the tension strut on the McPherson three-link front axle and the spring suspension link of the multi-link independent rear suspension are harder. As a result, driving through curves becomes much more precise. The noticeable gains in steering precision and spontaneity have been achieved without any noticeable loss in suspension comfort.

Dynamic-handling control systems comprehensively overhauled

All of the dynamic-handling control systems, such as the ABS anti-lock braking system, the braking assistant, the ASR acceleration skid control system, and the ESP® Electronic Stability Program, were reworked and modified in comprehensive calculations and test drives. For example, the acceleration skid control system now has a traction function when the ESP® is shut off. When a car enters a curve at high speed, the system determines when the back tyre on the inside part of the curve starts to slip and can brake it to a precisely calculated degree. The effect that is created corresponds to that of a mechanical locking differential and promotes the traction of the driven wheels. Even when shut off, the ESP® recognizes a potentially unstable driving situation, for example when the driver suddenly applies the brakes. Within milliseconds, the ESP is completely available again. A potential accident can thus be prevented. What's more, the control processes in all operating conditions have been made more harmonious. "

Expat

This is what puzzles me as when I've had the issue is on dry roads when I've been pulling out into traffic and I need to acelerate quickly and ESP cuts the power to both drive wheels making the situation worse not better.

PC Valkyrie

Maybe you're giving too much gas too quickly such that you overcome the grip of your tires. It can be a fine line with our high torque cars between keeping traction and losing it when you step on the gas very quickly. Are your rear tires wearing out?

Trekman

if your tires are worn would that be a problem?

Expat

The rear tires aren't new but there not near to the wear limit, I may need to replace them with better tires (e.g. PS2s) as a side note ESP seems to be doing a better job when I accelerate in a straight line so maybe the problem is really ESP + turning/corner + acceleration but this is where I expected it to make an intelligent difference rather than just cutting engine power.

cntlaw

Thanks for this information and until now I begin to know C55 is such a brilliant car for street race and safety

YeeHaw

so you re not gonna sell it for a gti/mini then?
:p