Brake By Wire
06-18-02, 09:34 AM
#1
Lexus Test Driver
Thread Starter
Brake By Wire
I understand that the new Benz SL has the brake-by-wire technology. I popped open the hood of the GS to see what's in our GS.
Well, it looks close except that the GS appears to still have a direct mechanical connection between the brake pedal and the master cylinder. It has no vacuum assist like in the old days.
Would someone please explain how the brake gets its boost? Electro-mechanical?
Well, it looks close except that the GS appears to still have a direct mechanical connection between the brake pedal and the master cylinder. It has no vacuum assist like in the old days.
Would someone please explain how the brake gets its boost? Electro-mechanical?
06-18-02, 02:12 PM
#2
Lead Lap
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Hi, whitels!
I can't give you a "when the earth was just a molten ball of fire" explanation, but "surface-level" explanation is:
There is no mechanical connection between the brake pedal and the master cylinder (I think). Instead, the computer analyzes the brake pedal input (pressure, rate, etc.) and translates it into appropriate level of braking at each wheel. I believe that the boost is provided by ~2000 psi hydraulic system (probably operated by electric motor(s) ).
The cool thing about this system is that it can adjust the braking pressure independently at each wheel (depending on available traction, cornering behavior, etc.). It can also go into "DefCon 5" by increasing system pressure and applying the brakes slightly, reducing the time it takes to activate the brakes in emergency situations.
I believe that GS's VSC can also brake each wheel independently, because I once drove at the limit of adhesion on an onramp and could definitely feel something going on down at the wheels: this way, I did not have to lift and adjust the car with the steering wheel (VSC did it for me). Perhaps, the merc's system can do it faster, as is the trend with everything new.
Hope that helps.
I can't give you a "when the earth was just a molten ball of fire" explanation, but "surface-level" explanation is:
There is no mechanical connection between the brake pedal and the master cylinder (I think). Instead, the computer analyzes the brake pedal input (pressure, rate, etc.) and translates it into appropriate level of braking at each wheel. I believe that the boost is provided by ~2000 psi hydraulic system (probably operated by electric motor(s) ).
The cool thing about this system is that it can adjust the braking pressure independently at each wheel (depending on available traction, cornering behavior, etc.). It can also go into "DefCon 5" by increasing system pressure and applying the brakes slightly, reducing the time it takes to activate the brakes in emergency situations.
I believe that GS's VSC can also brake each wheel independently, because I once drove at the limit of adhesion on an onramp and could definitely feel something going on down at the wheels: this way, I did not have to lift and adjust the car with the steering wheel (VSC did it for me). Perhaps, the merc's system can do it faster, as is the trend with everything new.
Hope that helps.
06-18-02, 02:56 PM
#3
Lexus Test Driver
Thread Starter
Vlad-
Sounds like the GS is also a "brake by wire" system based on your description. If so, then Merc better drop what they're saying as the SL being the "first production brake by wire car".
Sounds like the GS is also a "brake by wire" system based on your description. If so, then Merc better drop what they're saying as the SL being the "first production brake by wire car".
06-18-02, 10:50 PM
#4
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I see your point...
But if you think about it, lots of newer cars have stability systems that can brake individual wheel(s). That does not mean that the car has a brake by wire technology, because stability system functions independently of driver input (in terms of braking) to keep the car pointing in the right direction or from spinning its wheels.
You could argue that ABS is also a brake-by-wire technology as well (it controls the wheels independently). I would argue, though, that ABS simply monitors the wheels for lock up and pumps the brakes if it detects it: it does not care about how hard the driver is pushing on the brakes as long as the wheels are spinning (this is all over-simplified, I am sure, but you get the idea).
The mercedes is the only one that processes driver input (from the brake pedal) and translates it into braking without a mechanical connection.
It gets kind of blurry downstream of the brake pedal, though.... I am not sure what the difference is between the SL and GS mechanically, but I am sure that both (and a lot of other cars) have the ability to apply brakes without driver pressing the brake pedal.
To get more info, we need an MB engineer
But if you think about it, lots of newer cars have stability systems that can brake individual wheel(s). That does not mean that the car has a brake by wire technology, because stability system functions independently of driver input (in terms of braking) to keep the car pointing in the right direction or from spinning its wheels.
You could argue that ABS is also a brake-by-wire technology as well (it controls the wheels independently). I would argue, though, that ABS simply monitors the wheels for lock up and pumps the brakes if it detects it: it does not care about how hard the driver is pushing on the brakes as long as the wheels are spinning (this is all over-simplified, I am sure, but you get the idea).
The mercedes is the only one that processes driver input (from the brake pedal) and translates it into braking without a mechanical connection.
It gets kind of blurry downstream of the brake pedal, though.... I am not sure what the difference is between the SL and GS mechanically, but I am sure that both (and a lot of other cars) have the ability to apply brakes without driver pressing the brake pedal.
To get more info, we need an MB engineer
06-19-02, 02:01 AM
#5
Lexus Fanatic
Brake by wire? Big deal, with a crappy driver, the Merc is still going to crash...and with a good driver, they can do w/o brake by wire...
What concerns me is that with Mercedes KNOWN electrical problems, do you really want the brakes to depend on Mercedes' electronics?
What concerns me is that with Mercedes KNOWN electrical problems, do you really want the brakes to depend on Mercedes' electronics?
06-19-02, 09:55 AM
#6
Lexus Test Driver
Thread Starter
Originally posted by manaray
....
What concerns me is that with Mercedes KNOWN electrical problems, do you really want the brakes to depend on Mercedes' electronics?
....
What concerns me is that with Mercedes KNOWN electrical problems, do you really want the brakes to depend on Mercedes' electronics?
06-19-02, 03:04 PM
#7
Lexus Champion
Manaray..I was thinking about that too. What if it break down or something? I hope they have a back up or failsafe mode to stop the car. The new SL don't have the sway bar also.
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