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#1
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diference between brake assist and VSA?
It looks confused to me between EBD and VSA found on 06 Accord V6.
What is it and the difference? I understand the car's computer can detect slippage on one of the wheel and reduce the brake force on that tire but how can a vehicle detect the car is over/under turn at a curve like Honda website described? Anyone ever studied/experienced on this device? Like to hear if it is a real help and selling point for an 06. I have a 05 EX-V6 and wanted to get another 06 mainly for these "safety" feature. Thanks |
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#2
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diference between brake assist and VSA?
VSA stands for Vehicle Stability Assist. This system uses the existing ABS
components to slow or stop wheels on one side of the vehicle (side to side operation) to prevent over/understeer situations and to aid in prevention on vehicle control loss in emergency situations/maneuvers. "harry" > wrote in message news:jk2Rf.2720$3k1.2406@dukeread03... > It looks confused to me between EBD and VSA found on 06 Accord V6. > > What is it and the difference? I understand the car's computer can detect > slippage on one of the wheel and reduce the brake force on that tire but > how can a vehicle detect the car is over/under turn at a curve like Honda > website described? > > Anyone ever studied/experienced on this device? Like to hear if it is a > real help and selling point for an 06. > I have a 05 EX-V6 and wanted to get another 06 mainly for these "safety" > feature. > > Thanks > |
#3
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diference between brake assist and VSA?
Thank you for the response.
My next question is --is it duplicate function if brake force distribution can control the brake, why need VSA again? What does traction control's role? Sorry for all these questions, I am puzzled. I saw ABS first and then TC and the EBD and now the VSA. IS there any data/test reveals the effeciveness of all these so called safety features? |
#4
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diference between brake assist and VSA?
harry wrote: > Thank you for the response. > My next question is --is it duplicate function if brake force distribution > can control the brake, why need VSA again? > What does traction control's role? > > Sorry for all these questions, I am puzzled. > I saw ABS first and then TC and the EBD and now the VSA. > IS there any data/test reveals the effeciveness of all these so called > safety features? This is a confusing topic because there is a lot of overlap. The good news is that you don't have to understand any of it, to benefit from it. It comes down to what do you know and what can you do about it. You can know the speed of each wheel with ABS sensors. You can know how much throttle is requested and how much throttle is delivered to the driven wheels. You may even be able to lock the wheels together to some extent when delivering power. You can know how much braking is being requested. You can control the braking force exerted on each wheel independently. You could even have accelerometers that measure centrifugal force, but I don't know that they actually do this. (I'll bet the airbag systems have accelerometers.) ABS (Antilock Braking Systems) is well tested technology at this point. You want to stop fast, you stamp on the brake pedal hard. This might cause the brakes to lock up. The ABS sensors can detect this lock up and release the brakes. For threshold braking you want the brakes just short of locking up. Cycling the brakes quickly between locking and just short of locking is a very good approximation to threshold braking. Remember you can steer a car just with the brakes. If you brake the right front wheel, the car will pull to the right. If you brake the left front wheel, the car will pull to the left. If you steer the car while braking hard, different levels of braking can be applied to each wheel. It requires a great deal of skill to threshold brake and steer a car without ABS. With ABS it takes little skill to threshold brake and steer the car. You just brake really hard and steer. The ABS does all the hard work. Without ABS you have no way of independently controlling brakes force right to left, so ABS is has some actual advantages over non-ABS systems. The most common mistake in ABS cars is not to steer around the dangerous object while threshold braking. The second most common mistake is getting off the brakes when you feel the funny pulsing in the pedal. TC (Traction Control) has to do with controlling acceleration forces on the driven wheels. Because of differentials, the right and left wheel can spin independently. This is necessary in normal cornering as the inside wheel travels a shorter path than the outer wheel. In some situations the traction is better on one wheel than the other. Without traction control, much of the engine power goes to spinning the tire that has no traction and little power to the wheel that does have traction. You want the opposite of this. In off-roading this is a well know problem. Locking hubs are the traditional solution. You lock the wheels together (bypass the differential that allow the wheels to spin at different speeds). Some times this is done with electronically controlled clutches. Braking just the tire with poor traction looks a lot like traction control. Since the wheels spin together when they are locked together, power will be delivered to the wheel with traction. The wheel with poor traction can't spin any faster than the wheel with good traction. This is a complicated subject. There are many ways to skin the cat. Off-roaders love to talk about locking hubs and traction control. Find one. EBD (Electronic Brake Distribution) controls the ratio of braking force front to back. This is problem wheel know to sport bike motorcycle riders. Motorcycles has independent front and rear brake controls for a good reason. When you decelerate from braking more down force goes onto the front wheel and less on the rear wheel. This means that the front wheel is harder to lock up and the rear brake is easier to lock up. You want more braking force on the front wheel and less on the rear. In the extreme you can "stoppie" a sport bike where a great deal of braking force is applied the front wheel and the rear wheel lifts completely off the ground. Just before this happens the amount of rear braking force that can be applied without skidding goes to zero. Note that it is deceleration that causes this weight transfer. Normal sedans can't stoppie, but they are affected by front/rear weight transfer. At the very beginning of the braking, the rear wheels have good down force and braking capability. The harder you decelerate the more weight transfers to the front and the more braking force you want on the front wheels. This can all be done short of locking up the brakes with ABS. Sports car drivers might call this continuous (front/rear) brake bias control. VSA (Vehicle Stability Control) works in conjunction with the ABS to control over steer and under steer. The total side force on a tire is a sum of acceleration force, braking force and centrifugal force (force due to centripetal acceleration for the pointy heads). Front wheel drive cars like the Accord tend to under steer. Centrifugal forces acts more or less equally front to back. Only the front tires are driven. So at the extreme the front tires will tend to slide before the rears, because the have more side force on them. This causes the car to steer to the outside of the turn. Backing out of the throttle tends to solve this problem, so this isn't so bad. Rear wheel drive vehicles tend to over steer when power is applied vigorously in a turn. This causes the rear wheels to loose traction and steer the car to the inside of the turn. This is great fun, but a dangerous situation can occur. Backing out of the throttle may cause the over steer to stop. It can also cause the over steer to suddenly increase and spin the car out. Why is this? When you accelerate, weight transfers back and increases traction on the rear tires. When drop the throttle you lose this weight transfer, traction on the rear lessons (traction of the front increases) and the rear spins out to the outside of turn. Ask anyone who drove a Porche 911 hard in the bad old days before all this helpful VSA stuff. Judiciously applying brakes to each tire can steer the car (remember our ABS example) and overcome, to some extent, errors in judgment. |
#5
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diference between brake assist and VSA?
This is such a great in depth explanation!!
I copied and saved as word documents. Thank you so much. |
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