[DuncanNixon2004]

Well I've had the 04 for just over three months and have put nearly 11,000 kilometres on it mostly highway travelling and mostly in the Yukon where there are a lot of gravel roads with little traffic. Imagine a 250 kilometre road where you only see 5 vehicles and those within 50 k of a community.

Anyway due to this kind of driving I have only had one or two occasions in which hard braking was necessary. Since when I am braking hard I try to pay attention to which way the front end is pointing at all times. However I did notice on one occasion an icon appear on the dash briefly. I believe the manual refers to this as the VSC symbol.

Can someone explain the VSC? What it is? How it works? How it differs from ABS?

I have looked for some kind of explanation but obviously am looking in the wrong places. :shock:

On an unrelated note. With three bikes mounted on a roof rack and driving like a human being during the break-in period (ie at or below the posted speed limit 90 or 100kmh) mileage ranged between 6.9L/100k and 7.4L/100k. With 8,000k on the clock under the same circumstances (3 bikes) and driving like other drivers on the same road (between 15 & 20k over the limit of 100kmh) mileage drops to 10.2L/100k. Typically, without the bikes but with the rack, mileage ranged between 5.4L/100k and 6.7L/100k with the lower figure reflecting law-abiding driving and the higher figure indicating driving similar to my fellow travellers. Average for the 11,000k was 7L/100k. Just thought someone might fing this interesting.

Duncan

 

[ehurtley]

The best way to think of VSC is to think of it as the OPPOSITE of ABS.

With Anti-Lock Brakes, when you jam your foot down hard on the brake pedal, the car monitors the wheels. If they start skidding, it eases up on the brake pressure slightly for a moment to they have traction again with the road, then it applies them harder to see if the road can handle the harder braking pressure yet. It repeats until either: you let off the pedal enough to stop skidding, or the road surface becomes different enough that your harder braking pressure doesn't cause skidding.

Vehicle Stability Control works the same basic way for accelerating. When you jam down the gas pedal, the car monitors the wheels again. This time, instead of checking for the wheels going too 'slow', it checks for them going too 'fast' (i.e. 'peeling out'.) If it detects this, it eases up on the accelerator pressure for a moment until they have traction again, then it reapplies 'full' power, to see if full power still peels out. If it does, it just repeats until you either let off the gas pedal enough to stop the peel out, or the road surface accepts the amount of power you're trying to apply without peeling out.

They are complimentary technologies, just applied to different subsystems in the car's drivetrain. In the Prius, it makes sense to have both, since both acceleration and braking are computer controlled and not mechanically linked to the pedals anyway. (I don't know why VSC isn't standard, as it is literally just computer programming.)

 

[slider65]

Well, I might as well jump in with my first post. I think what ehurtley is describing is actually called traction control. which the Prius also has. The VSC can be thought of as skid control, which is why it came on during braking and not accelerating. It senses if your car is getting off-axis (i.e. skidding) in a stop and adjusts the braking and power to compensate and straighten you back out. In theory

Of course, I could be wrong - happens all the time, just ask my wife...

Tom

 

[john1701a]

Yup, that's traction-control.

VSC is different. It helps you recover when taking something like a corner too hard.

It works pretty cool. And if it wasn't for the beeps and the indicator light, you might not even realize the car just compensated for your over-estimation of the driving conditions.

 

[ehurtley]

Ah, you're right. I had it confused. VSC is the 'turning traction control'. Which I have no idea how the tech behind it works.

 

[SkipHuffman]

Prius on Rails

Ah, you're right. I had it confused. VSC is the 'turning traction control'. Which I have no idea how the tech behind it works.

Tell you what, all these things work like the proverbial bomb.

Driving through the remenants of Jeanne yesterday, the Prius (which my wife has named in Welsh so I cannot spell it yet) felt like it was on rails!

Usually when I drive in messy conditions, I push it a bit at first to feel out the road, try to get the wheels to spin a bit, try to skid a tiny bit into a stop. All so that I know what to anticipate for the rest of the drive. I could not get the new prius to do this! It was like driving on a dry road. Kind of eerie actually.

 

[DuncanNixon2004]

vsc

Thanks for all the info.

I guess I kind of understand now. I've never owned a vehicle with ABS. Last new vehicle was a 1970 MGB in 1970. It was a beautifully proportioned vehicle that only swapped ends when the road conditions were snowy/icy. Braking was almost intuitive.

Is there a technical paper out there that explains the VSC? Do many vehicles employ this technology?

As mentioned in the posts, when it does work you don't notice it.

As least now I know why, try as I might, I cannot peel out! 8)

Duncan

 

[KMO]

VSC in its simplest form adjusts the rotation of the vehicle by braking just one of the wheels.

For example, let's say you've pulled a hard left, and the car is understeering. The VSC detects that the nose isn't going in the direction that the front wheels are pointing in (using some sort of gyroscopic sensor), so it applies the brake on the left rear wheel. This has the effect of pulling in the understeer and getting the car going in the desired direction.

Similarly, oversteering can be countered by braking one of the front wheels.

The computer can control the car far more precisely than you can. It can control the brake pressure on every wheel independently to keep you on track.

The full VSC+ system in the Prius is more sophisticated than this simple description, mind you.

 

[Guest]

VSC

Here's a brief article on VSC that explains fairly well how this system works: http://www.canadiandriver.com/articles/jk/at_010320.htm

 

[DuncanNixon2004]

VSC

Thanks Phil.

A good friend who owns the Subaru (and pronounces it sooBARoo) could probably have explained this to me and lorded it over me that his system is superior had I asked him. I, personally, have never understood the attraction that Subaru has for people.

A good article that explains it well in layman's terms.

Thanks again,

Duncan

 

[Guest]

The VSC can be thought of as skid control, which is why it came on during braking and not accelerating.

Just to be clear to all, VSC works during braking, accelerating or coasting. As long as the directional stability is compromised and vehicle speed is greater than about 15kph, VSC will attempt to correct it.

 

[Guest]

Somebody please tell me how to disable the Traction Control. But, please don't try to convince me that it's wonderful and I should therefore reconsider.

 

[zinzindorff9]

My guess is "you can't do it", even with a really big hammer. Since I also believe it is a "standard option" I guess you have to pick some other car! All this is just a guess but I expect it is in the Prius manual.

 

[mrv]

Somebody please tell me how to disable the Traction Control. But, please don't try to convince me that it's wonderful and I should therefore reconsider.

There is no traction control off
switch. The only time where it is
not a useful feature is where you
have to rock yourself out of an
ice/snow patch...

There is a procedure in the repair
manual that'll turn off the
traction control (maintenance mode
I believe it's called), but there
are dire warnings about harm to the
transmission if you try driving
around with the traction control
off...

 

[Guest]

Why is there a turn off switch

I have an Infiniti I35 with stability control. There is a switch to turn it off. Why would anyone turn it off? What benefit would be gained?

 

[ehurtley]

From Car & Driver's article "Sport, Got Hybrid?&quo

You take complete responsibility for using any information quoted in my post. I assume ZERO liability, since I'm just quoting from a publicly available source. If you eff-up your car, don't come crying to me...

"Press the brake once!"
"Floor the gas three times!"
"Press the brake again and try it!"

Source: Car & Driver, November 2004

Since in the article, this didn't do it, this may not even be the right thing to do...

 

[plantz]

Re: Why is there a turn off switch

I have an Infiniti I35 with stability control. There is a switch to turn it off. Why would anyone turn it off? What benefit would be gained?

I have a friend who went to race driving school. He owns an Acura NSX and a Mercedes AMG. He tells me that if you really know what you're doing, you can do better than the various electronic systems. For example, one of the techniques for stopping without using ABS is to push the brake pedal until the wheels are just ready to lock up, then turn the steering wheel all the way to one side. This gives you the added braking power of wheels going sideways in the front.

My recommendation would be to try this at home! Do not try it on a public road!

Seriously, for 99.99% of us, the electronic things are MUCH better at helping keep us out of trouble. Although an expert driver might be able to do better without them, I don't think anyone should be allowed to drive that way on public roads.

 

[Deerpath]

I did a search on braking because I recently had to brake hard on the expressway at 75mph and turn into another lane at the same time. A car right in front of me lost a wheel .

I only have about 2500 miles on my 2005 Prius so this is the first time I have had to brake like that. Unfortunately I live 27 miles from work and the expressway is the way I get there so it's likely I will have to do this again at some point.

Anyhow the car fishtailed for a moment when it should not have. It felt for a few (very long) seconds I was not in control of the car.

My husband and I were trying to figure out if the weight in back or the VSC had anything to do with it. I would like to think it is just me getting used to the car. I've driven many years though and many cars, and have not had this happen before. Has anyone else experienced this?

 

[mrv]

on my 2001, when I was experimenting with differing tire pressures, a panic stop from ~40mph (darn Dunkin' Donuts uncaffienated patrons...) when the tires didn't have at least a +2psi in the front I found that my car would fishtail. With +2 (preferrably +2.5 or +3) my 2001 would just stick when I did the panic stops.

 

[Deerpath]

Thanks, we'll try that!