Traction Control

Jay,

I agree with your observation about how the traction control works on the Prius. I have never seen any evidence that it selectively applies a brake to the spinning tire. It appears to do all of its work by modulating the power. It's good to hear that there is a noticeable difference between the new trac and yours. I was starting to think that perhaps I'm just a Prius apologist, since it seems to work pretty well for me.

Thanks again for the good review,
Tom

 

Patrick

Good question. One would think, "yes." Most likely there are programmatic and hardware changes involved that take this beyond a simple Plug and Play approach.

Not sure if the Trac behavior has convinced me to get rid of my '04, but I am now thinking of it. Given the fact I already have 148,000 km on it, I'll probably have to sell it privately to a taxi operator.

 

Tom

Yeah, I brought it up as some on the forum have claimed the brake is applied to the tire that is slipping. That's how the optional VSC works - it will apply one of the front brakes. But right, no evidence the brakes are used for Trac

I'm familiar with how brakes are used for Trac assist, as that is how my FJ behaves. I tried out that feature last summer near the hobby farm, at an abandoned gravel pit. Found a washout to cross, at an angle.

Engaged 4L, pushed A-TRAC, and let it creep at an angle across the washout. Once a wheel was in the air, the brake was applied to that wheel. Didn't need to use the mechanical locker at all

Something tells me a 2008 Prius shod with the aggressive studded winter tires I now use on my '04 would be almost unstoppable. The only thing I didn't try was to drive it into one of the remaining snowbanks to see if I could "rock" it out.

With my '04, once it bogs down, it's impossible to rock. Just sits there and strains

 

I have rocked our 2006 on a number of occasions. It works pretty well.

Tom

 

Tom

Interesting. I would have to guess the 2008 I test drove would also "rock" without too much hassle. My 2004, once it bogs down, feels as if it is trying to strain, but nothing happens.

Doesn't matter if I gently press the gas pedal or floor it, cannot rock. The FJ will alternately apply the brake to the left and right rear wheel in an attempt to provide traction, and it will easily rock

 

With my 2006, I can rock it by pressing and releasing the accelerator. If I want to get a more serious rock going, I flip the shifter back and forth from D to R while holding the pedal down.

Tom

 

Tom

Well, it's quite apparent that some Prius cars out there - like mine - have the hypersensitive Trac algorithm. Driving that 2008 really convinced me of it too

Maybe should consider getting a new Prius, we finally have tax incentives up here to do so. I could also keep my studded winter tires, the OD is close enough between the new 16 inch and the 185 65 15 on my 2004

jay

 

just to add one more stat to the pile. We live on a steep paved road in Vermont and had many incidents of our 2005 prius coming to a dead stop and refusing to go up this winter - this with nokian studded hakks (usually during snows of more then 3-4 inches, quite common up here). We did have some luck with cable chains...the traction control would turn the front wheels about once a second or so, and, with chains, that was enough to move the car most days. On two occasions we had to go get our fj80 LC and pull it by the front tow hook (not fun on a cold winters night). As others have pointed out, on every occasion other cars were spinning their way up the hill without much issue. That said, we do love everything else about the car.

 

I too had the same problem with the TC despite changing over to snow tires. I recently moved to New England and live on a lake with my driveway having an incline. When it gets snowy, the prius would sometimes just sit there and do nothing when it detects excessive slippage.

When I am on-call and have to be at the hospital quickly, I have no time to shovel snow, let alone throw some sand on the driveway. After a couple of times of being STUCK up my own driveway, I ended up buying a Land Rover That truck can get out of a ditch!

I now drive my prius in the Spring and Summer and during light snowy days. Can't beat the over 40mpg compared to the 14mpg of the LR3.

 

Re: OK What Tires?

I wish I could be more specific but I just saw an ad, and I cant remember where, about a new tire with compressed air controlled RETRACTABLE studs. They can be controlled and only extend when you want them to. I am going to try to Google and find it again but would probably be a great thing for states that prohibit studded tires.

 

When I test drove the 2008 Prius, I thought it had improved the Trac response. However, comparing the Trac behavior to my FJ there is still a huge difference

With the Toyo Open Country G-02 Plus studless winter tires mounted, I leave my FJ in 2wd almost all the time. It has no trouble whatsoever

Different vehicles, different purposes

Now that the 4.5 km long gravel sideroad to my hobby farm is baddly rutted due to a small logging operation, it would be impossible to get my Prius in anyway. The FJ does a great job in that situation, and if I drive gently I get 26-28 miles per Imperial gallon

 

Living in North Alabama and driving an NHW11, I don't have much opportunity to understand the problems of traction control versus ice and snow. But I do try to keep a FAQ updated and recently wrote this:

Those who live in snowy, winter climates should mount quality ice and snow tires (marked with a snowflake in a mountain) in the winter season. On very slippery road and winter conditions, the 2004-2006 model year Prius with OEM or non-winter tires, the traction control can leave the car unresponsive even with the accelerator pressed to the floor. It does this to prevent useless tire spinning and transaxle issues. More recent Prius ECUs have an improved traction control system that will 'pulse-spin' the wheels in super slippery, icy conditions.
​

Now one question that came up is whether the change happened during the 2007 year models. I have two points of view on this but no way to tell.

I noticed some discussion of 'rocking' the car but I'm not sure that is what I want to put in a FAQ that should be specific to Prius versus something that sounds like a general technique.

I'm always interested in suggestions on how to improve the accuracy and clarity of the FAQ and thought I'd ask you' all.

Thanks,
Bob Wilson

 

Comparing a Prius with a 4 wheel drive like a FJ is kind of like comparing a formula 1 car to a Case tractor.

 

I have a 2007 and only had one problem this winter in Western NY in snowy conditions with the OEM tires. It was on a steep up hill where I wasn't able to get much acceleration turning into it. Basically I was starting from a near stop on a steep uphill during a snowstorm with a few inches on snow/slush on the road before it had it been plowed or salted. The power basically cut all together at first but it did eventually eek its way up the hill at about 1-3 MPH (didn't seem much like of a 'pulse-spin', more like mini pulse-no spin; it would cut out at the first sign of a spin I think, then try again and maybe make a bit of progress). Took forever and the row of cars behind me was pissed but I did eventually crest the hill. I have since gone up this same hill other times this winter with snow on the road and had little trouble (maybe a couple of minor power cuts but it generally picked right up). I think it was the slushy stuff (right around freezing temps) that was the culprit on this particular occasion. I was also more conscious to try to get a little speed turning onto the hill on future attempts.

 

Comparing the 2004 I have with the 2008 Prius I test drove 2 weeks ago was also silly. Toyota has clearly changed the Trac algorithm

It's also clear that Toyota has learned a great deal from the Prius. My FJ has many features borrowed from the Prius, such as electric assist power brakes

The 2008 Prius I test drove has quite a bit in common with my FJ Cruiser, at least as far as the Trac response. My FJ - in 2wd - never kills all the power. It very rapidly pulses the brake at the spinning rear wheel

The 2008 Prius I drove didn't appear to apply the brake to the spinning wheel, but it very rapidly pulsed the power to the front wheels. The power application was easily 3-4 times faster response than my 2004 Prius

So now that I have gone for a spin in a 2008 Prius, I can understand why some folks don't understand why a Prius would simply stop on you with a bit of snow underneath. It appears Toyota has resolved that issue

 

As a new poster I hope you’ll forgive me if I’m beating a dead horse. I just bought a new 08 Prius and took it on a weekend trip. I was staying in a cabin high on a hill accessed by a gravel drive. The steepest part is preceded by a sharp turn (switchback). I have negotiated this in a 2-wheel drive pickup truck with street tires with no problem. It took me 4 attempts to make it in the Prius. Each time I lost considerable momentum as the traction control switched power from one wheel to the other. On the failed attempts, the wheels ultimately just stopped turning – no power – and I had no choice but to back down the hill. I tried it slow and I tried it fast. Ultimately fast got me up but barely.

For those wondering if the “problem†has been solved in late models, I would say no. Since I have never driven the older models I can’t say if it has improved but clearly the issue still exists. I would wager there isn’t another car on the road that would perform as poorly on this hill. I’m very disappointed.

If anyone has heard of an acceptable solution to this I would be grateful.

 

I question the validity of the previous post. Prius traction control has no facility for switching power from one wheel to the other, it simply regulates torque to both front wheels. Perhaps the poster misinterpreted the power reduction as power transfer.

I have experienced problems with the traction control on steep gravel roads, particularly with the crappy OEM Goodyear Integrity tires. Our new Micheline tires work much better. Still, gravel is one of the special cases where spinning can help. Often you can toss enough loose stuff out of the way to get down to something more solid. The Prius will not let you do that. With the Prius it's important to maintain speed and floor the accelerator pedal when the wheels start to slip. With the new traction control the Prius will keep trying, unlike the old version where it would simply stop. Even with that, there are cases where you just can't get up a hill.

Tom

 

Since this is a known issue, I think it's insane that Toyota still hasn't installed a switch to disable it.

 

Well, I'm puzzled to hear the 2008 Prius still has some issues with gravel hills. With my 2004, it refused to climb a small hill similar to the one the previous poster described, when some of us from the office went to a fishing camp in NW Ontario. The co-worker with the VW Golf tdi and stick shift had no trouble whatsoever

The only sample set I have for comparison is my personal 2004, the 2008 I test drove, and my FJ, which also has standard, no-defeat Traction control

The 2008 I test drove *clearly* had far superior Trac response, compared to my 2004. If my 2004 wasn't so bad, I'd probably also dismiss outright any complaint of the Prius Trac system. As such, I at least try to consider the situation the Prius driver is facing

Steep gravel hills any vehicle can run into trouble. The weight transfer will shift backward, so a fwd car will spin and lose traction, everything else being equal

A rwd car with an "open" differential will just spin one tire and dig in, stuck. An empty pickup truck with an "open" diff will also just spin one tire

For a rwd car or pickup, a "locking rear end is a day and night difference. I put this unit in my Ford work truck at my hobby farm, and I only put the hubs in Lock when snow plowing

POWERTRAX® LOCK-RIGHT LOCKER BY RICHMOND

I wouldn't want a rwd car or pickup equipped with a locking rear end as a daily driver. The operation of the unit while turning a street corner is noisy and jerky. On icy surfaces, the rear end can also step to the side

I agree the Prius comes with pretty crap tires, at least mine did. However, others also have - perhaps sarcastically - suggested their Prius can charge through gravel and snow on bald tires, thus implying the driver was to blame

No easy answer here

 

The torque from MG2 would be completely unmanageable without traction control.

Tom