TRAC works and works well!!

We got a few flakes today...

As soon as we get 10 cm on the road (probably in December), I will test drive a Prius III on our 18% slope hill, and will post the results. With all-season tires, it shall be an interesting test for the TRAC system... (probably the worst possible case)

 

Does TRAC also manages wheel spins in the rear tires?

 

From what I read (from NCF doc?) that 2010 Prius would actually engage frictional brake pads in order to control wheel slipping. The traction control responsibility was moved from ECU to the brakes. I think that is a great move and makes more sense since, engine control would cut the power to gain traction.

 

I thought it did both? used the brakes on the faster turning wheel and controlled the amount of power delivered to the wheels. In fact I believe the Gen2 system did the same things as do most traction control systems. But the Gen3 system may allow a bit more wheel spin, one of the big problems with the Gen2 system was that it allowed virtually no wheel spin and you need a little or sometimes you can't move.

I'm not sure about the way it operates though because we haven't had any snow here yet. But I did notice the new TRAC worked better on dirt roads while starting out on steep hills.

 

There is no need for the traction control to do so the Prius is only driven through the front wheels. There is, however, another system called VSC that uses all 4 brakes and the throttle to help manage skids or loss of control. The TRAC, VSC, and ABS systems interact when necessary but I've never seen a good description of exactly how that works.

 

If it brakes the rear wheels when spin is detected, will the rear of the car spin around? I am asking because this happened to me with another brand's FWD when driven in snow.

 

VSC will apply brake action to an opposite corner if the vehicle starts to skid. The car will not spin around, as that is exactly what VSC prevents.

Tom

 

But if both rears are already loosing traction, wouldn't applying brakes to either of the rears induce an even faster spin? I guess I am wondering how does a Prius handle on snow/icy roads?

Thanks

 

ABS will not allow the wheels to lock - period. By spin I assume you mean skid. No, VSC and ABS will reduce the tendency to skid.

As for your real question, the Prius is the best winter driving car I have ever driven. It tracks straight, has no tendency to pull during braking, and VSC is amazing. What it isn't is a truck. You can't wade through deep snow like you can with a Jeep, but it drives a lot better than a Jeep as long as the snow isn't too deep for the low ground clearance.

Tom

 

I wonder: Does the Gen 3 ABS/VSC/TRAC use the pulsing technique like a normal car? I ask because a normal car uses solenoids in the brake system to pulse the brakes as a rather crude way of preventing lockup -- meanwhile the Prius is brake-by-wire which means the ECU can apply the brakes any amount it wants to any wheel individually without you even touching the brake pedal. Theoretically it could engage ABS without pulsing and just keep the tires on the edge of traction for maximum breaking. Same applies for traction control or stability control.

With less than 200 miles on my car I'm still being easy on the brakes so I haven't tested any of this yet.

 

Thanks for the test results Tideland. http://priuschat.com/forums/gen-iii-2010-prius-main-forum/70557-tested-out-trac-vsc-abs-tonight.html

 

I'm not crazy about that beeping. I guess it only kicks in when VSC is doing its thing? (But not TRAC?)

 

exactly!.. vsc is for skidding and skidding only... traction control is simply to keep traction to all 4 wheels.

in traditional cars without trac or vsc, they have a majority of braking applied to the front wheels.. mainly because more weight is up there. in snowing conditions, this makes the front end lock up faster causing the back end to wip around.

in a genII prius and genIII Prius... it brakes wheels individutally to kinda.. uh.. drag the car into a proper direction. it works well on just about any surface (not as well on loose gravel)

the GenIII has larger rear disk brakes to accommodate newer traction techniques... such as, inner rear wheel braking to help you turn faster

 

I think we 2010 owners owe a great deal of gratitude to the older Priuses and Prius owners. If it weren't for their inputs and real world experiences, I don't think the Gen III would be the car it is. I want to see what they come up with on the Gen IV.