Prius is a dangerous vehicle in snow

That could work, although I favor tighter control of wheel speed. That way we could do limited slip traction control like that used on diesel-electric locomotives.

Torque limiting clutches would not eliminate the over-speed risk to MG1, since MG1 can reach very high speeds with little torque. I suppose you could use a combination of a torque limiting clutch and active loading of MG1 to keep it under control. Either way, the system should be able to use selective braking, even they way it is now built.

Tom'

 

Nope, you cannot imply just because MG2 is smaller, it has less power. With the gearing in the Gen III, the higher power of MG2 , the force caused by MG2 at the patch of the tire is greater than in the Gen II.

MG2 in the Gen III runs at about 20 % higher voltage. Consequently, it can spin 20 % faster (higher voltage, higher back emf can be overcome). If the current is the same, then you get 20 % higher power.

Check out the specs. You will see it has a higher power rating. It also has a reduction gear set between it and the PSD.

 

Hi Zhe Wiz,

This is a very good comment - So I am going to repost it here for all the nay-sayers to read:

"After a lot of reading and some recent driving in horrible "lake effect" conditions, I can see where the variance of opinions comes from. The car is great in the snow...when you're moving. I followed a Mustang up some very slight hills. He was ALL OVER THE PLACE. So much so, I backed off fearing he was going to spin out. My car (08 Prius with Michelin X-ice Xi2's on all four corners) didn't even light up the traction control light. AND I was pulling a trailer, albeit an empty one, and one passenger and lots of hunting gear. I easily had 600 lbs of stuff not including me, most of the weight over the back wheels. The Prius was great!

The counter of that, is on the same trip, I had to stop at a stop sign, then turn right onto a fairly steep hill. I did it, started up, but traction was lost and I gradually began slowing down. Before I reached the top of the hill I was going to have to make a left turn, a very sharp left turn. Fearing that I would be unable to make it, I instead turned into the nearest driveway and turned around and went home...the deer weren't worth it. Would I have made that hill? Maybe, I'm not sure. It is possible, but it's also possible that I would not have, and backing down the hill with a trailer behind me wasn't something I wanted to try, so I took the "easy" out.

A week later I drove into a muddy field. A pickup, a REAR WHEEL DRIVE pickup, made it all the way up a fairly gradual hill. I couldn't make it as far as he was, the traction control kicked in and stopped me. Of course it was a muddy field, which (I think) is the worst possible scenario. Snow on top, grass under that, mud under that. Nothing really to grab onto, yet the pickup made it and I couldn't.

When moving, this car is awesome. VSC and ABS combine to allow you to do some really stupid things on snow and not even know you did those stupid things. That Mustang and that pickup would have been in a snow bank if I tried some of the things I did in the Prius (on purpose). Yet when it comes to starting from a stop, or recovering from a spin, the Prius' TC KILLS forward momentum and tends to get the car stuck.

With the same tires on an icy/snow covered road (Michigan Hill for those familiar with my area...Berkshire Prius, you there? I was able to make it up one side and down the other safely, but the up side I was able to get some momentum before attempting the climb, and the downside I kept on the snowy part. ABS and VSC kept me going. A four wheel drive SUV was having trouble getting up the hill... it was very slippery.

This is the dichotomy we see on here, at least that's my belief. This car can get thru a lot of poor conditions very safely, but starting from slow speed or a stop up a hill is NOT something it is at all good at. Normal driving on normal (but very slippery) roads is something it is VERY good at. Even if the driver sucks or is unaccustomed to slippery conditions, it will save you. Just don't ever stop on a hill, even a slight one under slippery conditions! And PLEASE make sure you have good winter tires. This car needs all the traction it can get, that's for sure. Once it starts spinning, TC kills you.

I bought chains, that was my solution. Hopefully I'll never need them, but they are there just in case. I've already wished I had my AWD Forester back once this year and it's barely December!

Jack
Dryden (near Ithaca) NY.

"

The Prius of course, does not do well in high centering situation, nor does it do well against pickups with off-road tires, off-road. And, yea, stopping at stop signs in the winter is kinda something people learn to ignore around here, in all cars. The more usual technique is to approach the sign at 3 mph, and time through the stop sign when there is no other traffic in the intersection.

If you do have to stop, then be prepared to accelerate very slowly, and do not get impatient. And this requires one to not rely on pedal feel, but on visual observation of acceleration...

 

Good thing then that Prius doesn't lock the wheel it simply cuts power to the drive wheels for what feels like forever but is actually a tiny fraction of a second.

 

Is Gen III optimal ? Until the root cause is known (or disclosed by Toyota), no one can be sure.

 

Yes.

Why not ? A clutch between the MG2 and the wheels will decouple MG2 rpms from the wheel, thus allowing the MG2/HSD complex to operate within its limits.

What exactly do you mean by "easy" ?
The only certain thing is that torque control and the response characteristics of EM and ICE's are totally different.

There's also need to protect the MG2.

So the torque at the same motor speed is lower in Gen III which is my point.

 

So will the same clutch between the ICE and MG2. Interested to know why you would consider one but not the other design.

 

I didn't say the MG2 in Gen III has lower power.

 

Hi tpfun,

I really did not say you said that either. I said you were trying to impy it by your "smaller / less torque" comment. And then proceed to specify the actual differences.

The point is that the power, and thus torque at low speeds, to the wheels from 3rd Gen Prius MG2 is greater than 2nd Gen Prius MG2, yet 3rd Gen Prius has better behavior on slipery surfaces.

Which gets to the point that the issue is not the hardware, as hardware with worse (3rd Gen has more torque to larger diameter tire and creates more force at wheel patch) charactistic for traction on slipery surfaces, performs better.

Which leave the operation of the hardware, either by the operator, or the computer control, or the interaction between the two as the issue.

 

LOL its fine.. Get the right tires and
Spikes-Spider®
Alpine Pro

Im in the midst of the storm that hit georgia.. ive gone out yesterday and today at work right now and its find.. PEOPLE down here don't know how to drive . its that simple with the help of Spikes spider alphine pro.

 

The sudden change in torque when a spinning wheel gets traction can stress the whole drive train. A torque limiting clutch in the half shaft would prevent any damage and lessen the requirement to totally shut down the motive force. Limiting the spinning wheel speed by using the brakes (as in a true traction control system) would prevent excessive MG1 speed while transferring some torque to the other drive wheel which hopefully has some traction.

JeffD

 

On my way home this evening, I got into some thick snow with too warm temps (34 - 36F), which creates really slick conditions.
I was following a sheriff that was doing 30 in a 50 zone... a good guide to how bad the conditions were.
When I had to stop coming through town (going 20 in the 30 zone), the yellow light would flash, and starting from a stop made the yellow light flash and the car skid slightly sideways until it got some momentum.

This is, in my opinion, NORMAL behavior for the conditions I was driving in. I allowed lots of stopping space, allowed lots of "get moving" time, and avoided sharp turns and braking on corners.

I think, however, that my tires might be getting a bit worn. I have the Hydroedges, and they have at least 50K on them. They are supposed to be a 90K tire, but they are losing their "bite"... before next winter, we'll replace them.

 

It looks like the Gen II to III TC update is just a software tweak. But good news then is that the new software should be doable in the Gen II as well.

Good luck to all.

 

That is how it works in my FJ Cruiser. One side can be on dry pavement and the other side on glare ice

In 2H, my FJ will easily move, the TC applying the brake to the wheel on glare ice. My '04 Prius would have flunked the test

 

I've been very happy with the way my car has handled the snow and ice.

 

Okay, since there are so many issues with Prius traction control...where are the side by side compares to 'normal' cars? I mean, your friends certainly have 'normal, safe' cars that could do much better in a traction test? where are these results? All we hear is "i bet my old POS would do better". Bring it on.

 

Someone cited an article in a Finnish (?) auto mag which allegedly speaks of the Prius' winter prowess.

Can you translate that ?

 

Article at Vuoden Talviauto 2010 valittu. Google translation at Google Translate.

 

I bought my '08 Prius in December of '07 and have made multiple winter trips to Minneapolis, a 1350 mile one-way trip through almost all of Montana, North Dakota, and Minnesota. I did several of those with the stock Integrities. I don't recommend that, but it got me through including one trip during a really horrendous blizzard. I put Blizzaks on the car for a winter trip over Christmas this past holiday season and hit a lot of snow, ice, wind, just generally ugly driving coming and going, and the car handled just great. I have found that the traction control can be tricky, but one learns to work around it, and the VSC is amazing, allowing relatively safe travel on very slick roads, including black ice conditions.

I believe the OP to be a troll, two posts total.......he's only interested in bashing Prii, not in discussing them.

 

Interesting thread and article.

I was a harsh critic of the TC in my wifes 04 Prius for a few years now until Ireland experienced a white out in Jan 10 and again in Dec 10.
Back in 2007, I nearly killed the two of us in it while pulling out from a petrol station in front of an articulated truck with one wheel on slippery grit
It was a manoeuvre I would have been quite comfortable doing in the FWD Opel Vectra I drove myself at the time but the TC in the Prius left me sitting half in the lane with the truck bearing down on us in a plume of tire smoke. It was the first time I'd experienced the TC in action and I didn't realise that it cut the power!! The car just found enough traction at the last moment to get moving again but it was a scary moment. I never trusted it after that and drove accordingly.

And theres the rub. The car didn't nearly kill me, I nearly killed myself through bad driving. I said above that I would have been happy to do it in my own FWD car but there's the problem, it still would have required hard acceleration to get out in front of the truck. In a normal car anything can happen from missed/wrong gears or broken cv joints to snapped timing belt that will leave you exposed in the same situation that the Prius TC will. You're supposed to judge the situation defensively. We all take chances every now and then (all the torque of the prius making it even more tempting than most) but don't go blaming the car when it goes wrong. The TC will only cut in when the torque you've selected with your right foot exceeds the friction available from the ground you have not read correctly. How is that the cars fault?

Admittedly, I do like to hear that the Gen III will allow a little wheelspin before cutting the power but the availabilty of better TC doesn't absolve the driver of his/her responsibility.

What changed my mind? The two big freezes we've had here in 2010. The Prius has been simply sensational in handling the ice. We're really not prepared for snow over here and the authorities ran out of salt and grit so all local roads were sheets of ice and a tire shop would not even know what a snow tire is let alone find a studded one. I was amazed at how well the Prius handled it even on normal tires. In the end I took it into a frozen over car park to get a handle on its limits. I found the Prius virtually unspinnable, the VSC is brilliant. I couldn't induce a slide by normal driving so used a jab on the parking brake to get the car into a broadside slide. It self recovered every time from silly angles. Its the most sure- footed 2WD car I've driven to date. I was as confident driving it as the Range Rover I drive for work. Yes the TC cut in quite a bit but that only serves to warn you to drive defensively.

So on the thread title? Is it a dangerous vehicle in snow? Not when driven with respect of the conditions.