Power lost on slightest spin of tires

According to the Edmunds article, ASR Traction Control does, in fact, holdback motive power. Who am I to argue with Edmunds.

Perhaps the Toyota design follows the standard. As I said in an earlier post, I am not an automotive engineer.

Having never driven another car with traction control, I don't know how other manufacturers design their (ASR)TC.

What I do know, is that momentary loss of traction in one driven wheel of my Prius stalls the vehicle for a frighteningly long time when traffic is fast approaching. In my other cars, this momentary loss of traction is no concern since the other three tires have sufficient purchase with the road and vehicle stability is not a problem. None of the my other cars have traction control.

If Edmunds is correct, most other cars will react in a similar way to the Prius in a traction loss situation. This is a concern a prospective buyer should discuss with any manufacturer's representative (salesman) during the car buying process. It does not necessarily preclude the purchase of any Toyota vehicle.

jrohland

 

Are you saying that any vehicle will completely shut down in a traction loss situation? I don't believe that for a minute..

Further, I sincerely doubt that most manufacturer's representatives (salesmen) will have a clue as to what you are taking about.

 

I wonder how many of the people having traction problems have Vehicle Stability Control.

The European crashtest (http://64.233.167.104/search?q=cach...it/Home/article_id_627.html+prius+E-TRC&hl=en ) states:

"The Prius is the world's first car to be fitted with Electric Traction Control (E-TRC). The system controls wheel slippage via ECB2 and the high-torque electric motor element of the Hybrid Synergy Drive. E-TRC is so quick in counteracting the incipient skid that the driver often won't even be aware of an intervention, nor will he or she hear the tyre squealing that is often associated with wheel spin.

Interconnected with ECB2 and E-TRC is Vehicle Stability Control Plus (VSC+) which is the world's most innovative stability control system. It works with the electric power steering system (EPS) to add steering torque assistance to the conventional stability control system, helping the driver get the most out of the car's performance potential by avoiding stability-threatening situations."

This may explain why some experience the problem and some don't. I do not have VSC and have not had the problem.

 

I got stuck twice on Christmas trying to get up the slushy, hilly drives to my sister's place in the Irish Hills. It felt like I had bottomed out - my tires gripping nothing. I'm glad I remembered the large screw eye which enabled us to easily attach a tow rope to the front end and get pulled out.

 

I asked this very same question a while back- is it really TC or is some aspect of VSC also involved despite the fact that the VSC light doesn't come on?? I drive a Classic, and it has TC, but I've never felt like the vehicle would ever stop dead, no matter what the circumstances- the Classic TC also cuts power when it detects slippage as well, but its threshold is evidently quite high as I have been able to spin the wheels under certain circumstances.. When the TC does cut power, it turns it back on in short bursts so you keep going, and you get full power to the wheels again when traction is re-established..

I've been told that the HSD TC works completely different, and perhaps that's true, but to completely lose all motive power doesn't sound like TC at all; it almost sounds like the VSC is engaging the brakes, which is what led to my question.. It would be an interesting exercise to get yourself stuck, then reach under and unplug the skid control ECU and see what pure traction control without VSC does on its own.. The only other explanation for the difference in TC operation that I can perhaps think of is that with the HSD, due to its higher voltage motors, spinning could create multi-kilovolt spikes that the electronics cannot handle (the THS-I in the Classic can apparently generate spikes as high as 800V despite being a 273V system; the HSD/THS-II being a 500V system would conceivably do double that or more)..

 

I had the opportunity to drive a rwd ford mustang with traction control on icy mountain roads. In that situation the traction control was confidence inspiring. Just driving around the parking lot, there were enough patches of glaze ice that I could have easily gotten stuck without traction control. When it did kick in, there was limited wheel spin, and you could feel the brakes modulating about 10 times a second to limit wheel spin. Not only did it effectively transfer power to the wheel that had better grip, but the rapid modulation of power was more effective than what I could do feathering the accelerator petal. The engine never stopped in these situations as happens in the prius.

I rented a prius for two days to see if I wanted to purchase one. The roads were dry, so not much of a chance to test the traction control system, but as I accelerated hard out of a corner, there was some minor wheel spin, and the engine/motor powered down for a second before recovering. I found that mildly alarming.

 

Thanks for your interesting post.

In my 2005, it doesn't feel like the brakes are being engaged. It's just a total loss of power. You can press the accelerator to the floor and there is no sound, just a complete loss of response from the accelerator.

If the VSC was kicking in, wouldn't the light on the instrument panel light up?

 

Tideland,
To be more clear. I was accelerating up a wet on ramp at about 30-50% throttle, I hit the slush, car started to coast, I let off the gas then eased back down on the throttle until my foot was on the floor. When I coasted out of the slush the engine started again. p.s. I have VSC.

 

Well if you pulled out into an area with "no" traction so as all 4 tires could not find grip, then I could see the car refusing to turn any of the wheels because they "all" slip.

But it should be able to effectively transfer the power to the tires with the best traction.

 

As I don't have the package that includes VSC, the only thing I am dealing with is the Traction Control System. I have been experimenting. To date I have tried two methods of over coming the problem: the first and seemingly the most functional, just stomp the gas and hold it down until the car begins to accelerate, then modify the pressure on the gas pedal as needed. The second is to feather the gas pedal pressing and releasing it very quickly. Both these methods seem to get the car to gain traction and moving more quickly than it would lef to its own devices.

 

Are you saying that the Prius is a 4 wheel or AWD system? Obiously, it's not. I know you have been on PC a long time and know what you are talking about so there's a good liklihood I'm missing your point.

As I see it, the car is not "refusing to turn any of the wheels." I see this as implying there is power but it can't be used because the wheels are slipping. The situation I'm describing is where the power just shuts down, there is no wheel slippage, and you are just dead in the water. It's very frustrating and potentially very dangerous.

 

To take a step back, one thing I really have enjoyed about the Prius is the way it has turned me into a much smoother driver. The acceleration lag means I can't count on the Prius to jump forward from a stop like many other cars. So I end up planning my acceleration a bit more... I start to press the accelerator a little bit before I know I'll need it and and I get a smoother start. Passengers in my car comment on how smooth and luxurious it feels, like it's getting up to speed effortlessly. Obviously that is also a result of the variable transmission.

Coming from a sporty car, the Prius has mellowed me out and I no longer feel like I have to be able to dart out in front of traffic and instantly accelerate up to speed. I think this makes me safer.

The traction control continues this smoothness theme of the Prius. Yes, it does cut in and slow you down more than wheelspin would slow you down in a car without traction control. And sometimes that is annoying. But I think it also contributes to being a safe driver. Instead of being able to count on wild wheel spin to get me up to speed with the possibility of dangerous loss of directional control, I know that the traction control will always get me up to speed with full directional control, just perhaps a bit more slowly than otherwise.



It really comes down to the question of whether more power is really safer... is the 800 hp sportscar safer than the 125 hp Prius because it has the ability to merge into approaching traffic instantaneously? I would say if you are relying on all that power to do your merges then you are driving less safely than you would if you drove the Prius within it's limits- only merging when you have a larger cushion of safety.


As far as my actual experience with traction control, I have only had one time Prius TC might have been a problem for me, when I was driving an unplowed snowy road where tire tracks in the snow were a little deeper than the ground clearance of the Prius. The drag of the show on the car underbody caused traction control to activate and I slowed down sometimes. I was about a mile from civilization and it was getting dark and cold so I was a bit nervous. I realized that the road was unpassable but there was nowhere to turn around. So I backed up about a mile in the ruts. By maintaining momentum I was able to get back to the plowed road without incident. The whole time I was nervous about getting stuck and not being able to rock out of a potential stuck place. But it never happenned.

On my usual commute route home there is a place where I often have to stop at a red light on a steep uphill. When it rains I have had problems with tire slippage starting up there in all the non-TC vehicles I've had. But the Prius TC slows the car and then it cruises on up to speed like a safety champ.

 

Just sell the damn car. The rest of us actually like the safety features of the Prius. Sheesh, get over it, all of you who have this notion that the Prius is a perfect car. If it doesn't live up to the hype, get rid of it. Many find this a great car. I just get sick of all the whining when the Prius is NOT the car for everyone. Is it that hard? I just had to chime in here...flame on...

 

Has it snowed in South Dakota yet? Once you get some ice or hardpacked stuff you will rapidly join the ranks of the whiners.

 

yes, it has snowed. Got some snow tires. No troubles at all.

 

OK, just wait until the conditions are right. I'm assuming your conditons are the same as ours which probably is not be a good assumption. We get a lot of black ice, packed snow and freezing rain.

 

okay, I'll wait. I do not like to drive in that stuff, but the Prius is doing fine in my book...and I've owned a CJ Jeep (pretty short wheelbase, pretty scary ice performance, even scarier fuel economy), a 2-door Pathfinder (4wd, great vehicle, but with awful tires it, too, would get squirrely on the packed snow/ice... too light in the back-end). So far the Prius has been the better vehicle in those conditions. Now the deep snow...the higher ground clearance of my past vehicles trumps the Prius. I now wait for the plows after the 12" snowfalls!

 

I'm with you finman on how its easy to get caught up in the hype and expect perfect on all levels......
I don't think thats what is going on however, its understood that feathering, braking etc are all a little different with the prius....

the unnerving part is if you have your family in the car and get stuck in an intersection without the ability to move no matter how hard you press the accelerator?
If there is absolutely no traction, then no one else should be able to make it through the intersection either, but if there is traction, and the power is not being transfered properly to the non spinning tires, then i see the arguement has merit....
I have never been in that situation yet... as I don't own my prius yet... but if the case is true..I too am concerned, but if its extremely isolated, then I don't know if its user error, or a dangerous defect that needs to be addressed.

 

I want to share Popoff's concerns about the Prius on snow. I have been stuck with a dead-in-the-water car going up my driveway with rough ice, only because I stopped for a moment as I was going up. The car would not move or do anything at all. Being in my driveway, I just backed up, and came up again at full speed. It worked. But....it would not work if this were to happen on a snowy uphill high traffic road, going to work in the morning. With cars in front and back, and a traffic light ahead, one cannot control what situation they will be in when the car goes totally dead (this has also happenned to me, with considerable embarrassment!). I believe that all of us should send a message to whoever is listening from Toyota to do something about it. The situation is dangerous and not acceptable.

 

The subject of the Prius traction control has been gone through more than once on this and other forums. Some people say it's faulty and dangerous and others say it's fine. I've been through a winter with my Prius (plus part of this one) and am among the "fine" group. A friend of mine has been through 2+ winters with his (and has driven about 70k miles in it BTW) and I believe he feels the same. And in case anyone's wondering, we do have snow, ice, and hills in northern New England.

This is the first car I've owned that has traction control. It can be disconcerting when the car cuts the power when you try to accelerate on a slippery surface. But I think it is doing a pretty good job giving traction to the front wheels and keeping the car under control. I'm sure it's not perfect but I don't think it's seriously flawed either.

I've read the horror stories of people stuck on hills or "dead in the water" pulling into traffic. I wonder if anyone has done any scientific studies comparing the Prius with other FWD cars in the same situations. Both with and without traction control would be best. If the Prius performs worse than other FWD cars with TC then that's something to complain to Toyota about. Just saying that your Prius got stuck doesn't mean much all my itself. Every car I've driven has trouble in the winter at some time or another.

Another thought I'd like to share is that TC only kicks in when your drive wheel (or wheels) slip when you accelerate. If you can prevent such slippage, say with better tires or different driving technique, you'll always be better off.