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Anyone have info on the Electronic Brake Distribution system found on the 2003 GTI VR6? I'm curious, does it act as an anti-lift/anti-dive system to keep the car from leaning forward when braking?
Thanks.
 

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Re: Electronic Brake Distribution (UberGTI)

bump i did a search and this thread came up...guy never got an answer, and i was wondering my self how exactly this system works/when it works ect.
 

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Re: Electronic Brake Distribution (Banditt007)

I have to admit Imj alittle curious as well. But like was previously stated "It's doing a crappy job" lol
 

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To truly limit brake dive beyond just modulating the rear brakes to drag the rear a bit, the car would need active suspension. Last time I checked, we don't have active air or hydro springs or dampers :-(
 

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Re: (AlecGTI)

Quote, originally posted by AlecGTI »
To truly limit brake dive beyond just modulating the rear brakes to drag the rear a bit, the car would need active suspension. Last time I checked, we don't have active air or hydro springs or dampers :-(

Right on http://****************.com/smile/emthup.gif
 

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Re: (Jcr1982)

It does have electronically distrubuted brakes, as opposed to a manual proportioning or metering valve. Its all controlled by the ABS controller. Its not a matter of keeping the car from diving, but more distrubuting more braking force to the front brakes as the inertia exerted from braking causes the front to dive and the rear to lift. Older fords like the Taurus had a height sensing proportioning valve that was attatched to the rear control arms, as the rear end lifts due to the braking and diving of the front end, it actuates the valve the further up the rear goes the more force is distrubuted to the front brakes. Thats essentially all the electronic brake distribution in our cars does, aside from all the ABS events and such as well
 

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Re: (BigBlockBug)

if the rear was lifting why would you apply more force to the front brakes? that woudl cause an even more dramatic rear lift. i think you just worded that wrong, or your physics just arent working today

anyways the brake distribution has nothing to do with nose dive, the only VAG vehicles that will remain level when you slam the brakes are the A8/S8 pheaton, RS6 and thats about it.
basically since our vehicles have ESP you need 4 way electronic brake distribution, simply for the reason that it works off throttle modulation AND brake force in whichever corner is needed. in order to put brake force on only 1 wheel to correct a stability problem you need to have independent brake modulation capability. this also helps the ABS work better in full lock situations. in a conventional car you only have front rear modulation if any modulation at all. if 1 of your wheels locks your ABS will kick on but on most cars ALL brakes start to puslate so this means the wheels that have grips are no longer using their advantage to stop the vehicle and stopping distances actually increase. in our cars if 1 wheel starts to lock only that wheels brake will pulsate and the other 3 will continue full braking force until lock is achieved if at all. what that does is stop the vehicle a lot faster then a conventional ABS system.
basically works by using 4 independent wheel speed sensors hooked to the ECU which is hooked to a control unit for the ABS basically is a 4 channel booster pump so you have 4 wheel independent braking. and in that case the people who say its not working well your crazy, the system actually works incredibly well. if any of you have actually been in a situatin where you need to stop NOW it actually works.
 

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Re: (2002gtibluvr6)

Could always get the prodrive suspension, its got everything the guy above listed plus a bag o chips. But then again, I know the one for the STi is about 2800 in parts alone lol
 

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Re: Electronic Brake Distribution (colossus)

no its not search for the active susension from Bose. Yes Bose, do a search for "learning center" and Bose suspension. thats all I remember there are some vids that prove it is possible
 

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Re: Electronic Brake Distribution (BigBlockBug)

Quote, originally posted by BigBlockBug »
no its not search for the active susension from Bose. Yes Bose, do a search for "learning center" and Bose suspension. thats all I remember there are some vids that prove it is possible

Sounds like snake oil to me. A suspension on a car. Brought to you by the same people that sell a $500 'wave radio' with a remote that's so cheaply made it uses a membrane as a keyboard? I'll pass

http://www.fiendation.com/300zx/bosefaq.htm
The chassis dives/squats because the center of gravity is above the line formed by the front and rear hubs, looking at the side of the car. A moment is induced that is proportional to the vertical difference between the center of gravity and the line formed between the hubs. The higher the ride height, the greater the dive/squat, all things being equal.
Preventing vertical motion with a device that can only oppose horizontal rolling- after all, that's what brakes do- is impossible. It's like saying you can scale a smooth wall by pressing really hard against it. Physics aside, if there was ANY way to use braking to prevent squat or dive, Formula One would have done it already.


Modified by colossus at 10:23 PM 3-19-2005
 

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Re: Electronic Brake Distribution (colossus)

download the video then tell me that, im not saying it eliminates it completely, there is almost never such a thing as 100% in physics, but its damn close from what i can see
 

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Re: Electronic Brake Distribution (BigBlockBug)

Quote, originally posted by BigBlockBug »
download the video then tell me that, im not saying it eliminates it completely, there is almost never such a thing as 100% in physics, but its damn close from what i can see

There is NO way it can eliminate any of it. Physics is 100% certain on this. As it is on many many things.
Look at the car from the side. If you resolve all motion into two vectors- vertical and horizontal, then add them up. A vector acting along the horizontal axis cannot cancel out anything on the vertical axis. It can only move the line of action. Braking will only be horizontal.
I'll pass on a video; I'd take some certified telemetry as gospel for this one, including chassis specs. For all we know, they might have loaded weights on the undertray to reduce the dive.
Like I said before, if F1 hasn't used this, it's not viable.


Modified by colossus at 2:09 PM 3-20-2005
 

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If I may weigh in again:
Yes, physics some present true limits to what automotive systems can do. However, with technology we can toe that line ever closer. While a braking system cannot really help brake dive and other undesirables, a suspension can. An active suspension such as the Bose, Praxair, Magnaride systems can sense and almost instantly adjust suspension travel, stiffness, and damping to compensate for manuevers. For instance, if you're braking hard and your suspension instantly stiffens in the front, you'll limit nose dive. After the manuever, it adjusts back to default level. The same with cornering. Just as ABS/traction systems can use individual brakes to control the car, minute and concentrated suspension adjustments can limit roll, dive, and increase traction and control.
And they didn't put weights in the car to make the suspension look better, that accusation is pure ignorance.
 

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Re: (AlecGTI)

Quote, originally posted by AlecGTI »
If I may weigh in again:
While a braking system cannot really help brake dive and other undesirables, a suspension can.
And they didn't put weights in the car to make the suspension look better, that accusation is pure ignorance.

If you're going to toss words around like 'pure ignorance' you might want to get down from your pedestal and read the first post.
It asked about using brakes to prevent dive, which was the only thing I was discussing. Thank you for reinforcing my point.
 

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Re: (colossus)

how could you stop the car from diving? The physics is right, it dosnt lie... GTI's arent that top heavy, but the front end is going to dive when you push on the brakes. The harder you push the more it will dive. If you had some sort of active suspension that could dynamically increase the stiffness of the suspension as you were braking, you could reduce it. Even if you ONLY stopped with the rear brakes the car will dive forward a bit.
Quote, originally posted by Website from above... »

Newtons laws apply here. Really the third one is all we need to worry about right now.
The third law: Every force on a car by another object, such as the ground, is matched by an equal and opposite force on the object by the car. When you apply the brakes, you cause the tires to push forward against the ground, and the ground pushes back. As long as the tires stay on the car, the ground pushing on them slows the car down.
Let us continue analyzing braking. Weight transfer during accelerating and cornering are mere variations on the theme. We won't consider subtleties such as suspension and tire deflection yet. These effects are very important, but secondary. The figure shows a car and the forces on it during a ``one g'' braking maneuver. One g means that the total braking force equals the weight of the car, say, in pounds.


In this figure, the black and white ``pie plate'' in the center is the CG. is the force of gravity that pulls the car toward the center of the Earth. This is the weight of the car; weight is just another word for the force of gravity. It is a fact of Nature, only fully explained by Albert Einstein, that gravitational forces act through the CG of an object, just like inertia. This fact can be explained at deeper levels, but such an explanation would take us too far off the subject of weight transfer.
is the lift force exerted by the ground on the front tire, and is the lift force on the rear tire. These lift forces are as real as the ones that keep an airplane in the air, and they keep the car from falling through the ground to the center of the Earth.
We don't often notice the forces that the ground exerts on objects because they are so ordinary, but they are at the essence of car dynamics. The reason is that the magnitude of these forces determine the ability of a tire to stick, and imbalances between the front and rear lift forces account for understeer and oversteer. The figure only shows forces on the car, not forces on the ground and the CG of the Earth. Newton's third law requires that these equal and opposite forces exist, but we are only concerned about how the ground and the Earth's gravity affect the car.
If the car were standing still or coasting, and its weight distribution were 50-50, then would be the same as . It is always the case that plus equals , the weight of the car. Why? Because of Newton's first law. The car is not changing its motion in the vertical direction, at least as long as it doesn't get airborne, so the total sum of all forces in the vertical direction must be zero. points down and counteracts the sum of and , which point up.
Braking causes to be greater than . Literally, the ``rear end gets light,'' as one often hears racers say. Consider the front and rear braking forces, and , in the diagram. They push backwards on the tires, which push on the wheels, which push on the suspension parts, which push on the rest of the car, slowing it down. But these forces are acting at ground level, not at the level of the CG. The braking forces are indirectly slowing down the car by pushing at ground level, while the inertia of the car is `trying' to keep it moving forward as a unit at the CG level.
The braking forces create a rotating tendency, or torque, about the CG. Imagine pulling a table cloth out from under some glasses and candelabra. These objects would have a tendency to tip or rotate over, and the tendency is greater for taller objects and is greater the harder you pull on the cloth. The rotational tendency of a car under braking is due to identical physics.
The braking torque acts in such a way as to put the car up on its nose. Since the car does not actually go up on its nose (we hope), some other forces must be counteracting that tendency, by Newton's first law. cannot be doing it since it passes right through the cetner of gravity. The only forces that can counteract that tendency are the lift forces, and the only way they can do so is for to become greater than . Literally, the ground pushes up harder on the front tires during braking to try to keep the car from tipping forward.
By how much does exceed ? The braking torque is proportional to the sum of the braking forces and to the height of the CG. Let's say that height is 20 inches. The counterbalancing torque resisting the braking torque is proportional to and half the wheelbase (in a car with 50-50 weight distribution), minus times half the wheelbase since is helping the braking forces upend the car. has a lot of work to do: it must resist the torques of both the braking forces and the lift on the rear tires. Let's say the wheelbase is 100 inches. Since we are braking at one g, the braking forces equal , say, 3200 pounds. All this is summarized in the following equations:

With the help of a little algebra, we can find out that

Thus, by braking at one g in our example car, we add 640 pounds of load to the front tires and take 640 pounds off the rears! This is very pronounced weight transfer.
By doing a similar analysis for a more general car with CG height of , wheelbase , weight , static weight distribution expressed as a fraction of weight in the front, and braking with force , we can show that

These equations can be used to calculate weight transfer during acceleration by treating acceleration force as negative braking force. If you have acceleration figures in gees, say from a G-analyst or other device, just multiply them by the weight of the car to get acceleration forces (Newton's second law!). Weight transfer during cornering can be analyzed in a similar way, where the track of the car replaces the wheelbase and is always 50%(unless you account for the weight of the driver). Those of you with science or engineering backgrounds may enjoy deriving these equations for yourselves. The equations for a car doing a combination of braking and cornering, as in a trail braking maneuver, are much more complicated and require some mathematical tricks to derive.

There you go equasions and all. Its really hard to explain this with text, heh if I could explain to someone in person with some paper to write on it would be much easier. But basically, when you brake the car will dip forward, period. Just as concrete as the fact that when you apply the brakes, you will slow down.
 

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Re: (PhReE)

Oh, and to answer the primary question properly, no the electronic brake distribution is there to stop the ca as quickly as possible, USING the facts from the physics. Why do you think there is a front brake bias, why do you think the front discs are much bigger? Because when you apply the brakes you get more force pushing down ont he front tires than the rear so you might as well apply more braking force there. The stuff is just designed to best utilize the forces that (automatically) apply.
 

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Re: (PhReE)

Bingo, thats all that needs be said, and as for the ignorance above about just beleiving the telemetry to be gospel rather than open your mind and look at the video http://****************.com/smile/emthdown.gif , thats what seperates a discussion from an argument. So you can argue all you want from your myopic view of what yopu think you know about cars. Why not branch out and consider an approach or idea and contribute to the share of ideas. Thats what ruins this forum too many people that just piss every one off.
 

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Re: (BigBlockBug)

Quote, originally posted by BigBlockBug »
Bingo, thats all that needs be said, and as for the ignorance above about just beleiving the telemetry to be gospel rather than open your mind and look at the video http://****************.com/smile/emthdown.gif , thats what seperates a discussion from an argument. So you can argue all you want from your myopic view of what yopu think you know about cars. Why not branch out and consider an approach or idea and contribute to the share of ideas. Thats what ruins this forum too many people that just piss every one off.

Dude, PhReE just nailed Colossus' point home and you're still calling him ignorant? Physician, heal thyself.
 
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