Prius is a dangerous vehicle in snow

What is "Snow"?

 

Stuff Nobody Obviously Wants

 

Well, this is just not correct. If it was, we would not see all the efforts to add more ratios, and apply dual clutches, to reduce shifting times. Traditional gear boxes do a poor job of matching engine performance to road conditions, and another evidence of this is the initial application of Traction Control systems in the first place - in the 1990's.

I am not sure where you are getting this "one-speed" transmission stuff from either. Because, that is not true, and I think you are confused on this point. The Prius has a wider ratio range, which is continuous, and thus and infinite number of "speeds". I had hoped that you would eventually explain this to us, but you haven't.

The issue is how quickly the Prius can change speeds due to the electric/electronic nature of the speed change mechanism, and how that leads to the loss of static friction on slick surfaces. Its this operational detail that a Prius driver can easily learn to tune to avoid slippage in all but glare ice situations. The abiliy to change gearing rations quickly is a feature, which on good road surfaces, with good tires, is highly desired. Or else VW et all would not be putting all the money into DSG gearboxes.

I have put forward the theory that the low movement pressure of the accelerator pedal is at the heart of this issue. Which has been supported by the experiece of another poster indicating in the Gen III ECO mode having much better capability of the driver to avoid slip/TC limit events.

 

Wow, now that's uncalled for. What's your beef ?[/QUOTE]

Correct me if I'm wrong here, but the original poster described his actions being that of a complete jerk who tried to race out in front of oncoming traffic at a stoplight to make a left hand turn just has the light turns green (rather than waiting for traffic to safely pass).

I take safety VERY seriously.

 

^^^ as in a 'Jersey left'?

 

I checked my sticker (yeah, I kept it): the car came with TC standard, and Package #4 had VSC. I don't know which one triggers when we drive over even slightly compromised traction surfaces -- I'd assumed it was TC. And my apologies, I meant to write that the paint stripes were wet. We don't slip on dry paint/crosswalks, but the car routinely spins wheels and engages TC (or whatever) if the paint is even slightly moist. The original Goodyears would spin on wet, flat pavement.

We (I) chucked the stock tires pretty quickly. The next set, Yokohama Avids -- a model I've used before on other vehicles -- wasn't much better. The current Kumho Solus KR21 (tied for highest user rating at Tire Rack) are better, but the "sorry, no power" thing is still an issue more than any other car I've ever driven.

As for the BT plate, no. The Prius is the primary hauler for my wife and child, and I'm just not willing to add mods to a vehicle serving that role. Paranoid or over-protective, perhaps, but here I am.

 

Yeah, and my Pinto is safe, as long as no one rear ends it too hard and it doesn't burst into flames.

Not buying this argument, sorry.

Yep, it was a painted crosswalk line that caused problems for me, too. I'd have to cross it every morning on the way to work. Once I realized how intrusive the TC was, I'd always think about where the line was and place the car just past it so the tire wouldn't lose traction. Sometimes I'd even drive to another intersection to avoid it. That seems a bit excessive to me. And no, this wasn't on stock tires.

 

The Prius HSD is always in "top gear". Under start/low speed conditions (which is the focus of this thread), the MG2 is the primary source of torque to the wheels and the MG2 is directly connected to the wheels with exactly one gear. The combination of a high torque electric motor and its direct link to the wheels is the root of the problems people have been experiencing with low speed traction.
At other speeds, yes, the Prius has an infinite number of ratios.

That's one half of the issue, which by itself is not necessary a problem but when combined with the direct connection between the MG2 and the wheels, leads to the traction problems. There really needs to be a clutch between the electric motor and the wheels.

Yes, better driver awareness, tires, throttle changes in Gen III and the retuned MG2 (smaller and reduced torque from what I read) can only help.

 

Everyone makes a left turn in front of oncoming traffic under normal driving conditions. Nothing unusual about that maneuver. Why you would label everyone who does that "a complete jerk" is beyond me.

 

Huh? In the event you have no protected left turn (no green arrow), you're supposed to give right of way to the oncoming traffic before turning left. You should only go once any remaining oncoming traffic is a safe distance away.

I can't find a specific clause in the CA driver's handbook on this at the moment but found NYS DMV - Driver's Manual - Chapter 5, for instance.

 

One can turn left if you can do so safely even when there's "oncoming traffic", this is not in violation of the ROW traffic laws. Of course, no safety margin is guaranteed to prevent accidents and when the car does not perform as expected, the safety margin is compromised (which is the point of the OP).

 

I think you were replying while I was editing my post. One should only go once the initial oncoming traffic has passed and only after any remaining oncoming traffic is a safe distance away.

It's unclear to me if the OP cut in front of the initial oncoming traffic to turn left, right as the light turned green (as some are implying) which to me sounds dangerous and illegal OR if he didn't allow enough of a safety margin, which would be driver error. If there were an accident, I'd expect him to be cited as well.

 

Yes, it's true that there is fixed gearing between all of the moving parts, so mechanically there is one gear ratio. However, an effectively infinite number of virtual gear ratios are achieved through the serial electrical path. Virtual gearing is effective at all speeds.

Direct connection of MG2 is not the issue, nor would a clutch on MG2 help. Torque control of electric motors is easy, and in fact is much easier than with a gasoline engine. This is how diesel-electric locomotives maintain excellent traction even with metal to metal driving surfaces.

The real issue with the Prius is avoiding damage to MG1 during traction transients. Sudden changes in traction under load can send MG1 spinning to very high speeds. If we were to eliminate the gas engine this wouldn't be a problem. A Prius driven only by MG2 would not need the protective traction control currently used on the Prius. Putting a clutch between the ICE/MG1 and the rest of the HSD would help, but wouldn't be worth the complexity and loss of power.

MG2 on the Gen III produces more effective torque than on the Gen II, as the new system is geared. It develops less torque at the motor shaft, but turns at higher speed. Overall it produces more power, resulting in higher usable torque to the wheels.

Tom

 

I'm with the OP, although not in quite as dramatic fashion. See my post here: http://priuschat.com/forums/gen-ii-...vably-poor-performance-snow-2.html#post755539

Some Prius owners like to bury their heads in the sand on this subject, but it's a real problem and it is NOT NOT NOT solely due to the driver, the tires or their footwear (Really?). The traction control SUCKS.

I have another story to relate. Last summer in perfect, sunny conditions, the traction control on my Prius left me stuck. I was attempting to climb a moderate hill on a seasonal limited use road. Essentially it was dirt and gravel. I started up the hill and in the middle of the hill there was a rather sharp corner, I could not go very fast or I wouldn't have been able to make the corner. The front tires slipped on the gravel/dirt as I approached the corner, the TC kicked in and STOPPED my forward momentum, what little I had. I tried again, no matter how hard or lightly I pressed the throttle, the car would no longer go ANYWHERE. Sometimes it would give me a half spin, I'd start to move, then the TC would completely stop the wheel. Other times it wouldn't turn AT ALL. I had to back down the hill. Couldn't make it up. And this is a 2008 Prius, SUPPOSEDLY a version with better TC. If it is better, it still sucks.

You can make all the excuses you want, but I'd let you pick ANY 10 NON-HYBRID cars you wanted to and I GUARANTEE I could get all 10 of them up that hill in the same situation. The traction control on the pre 2010 Prius is HORRIBLE and I can see it as dangerous in some situations.

My solution? Right now we own two Priuses here in the northeast. I'm selling one and replacing it with an AWD Subaru Impreza Outback Sport. The payments plus gas will be about the same price as a Prius plus gas at $3.75/gallon. I'll give up a few features (keyless entry, auto climate control, backup camera, leather seats are the biggies), but I'll have a car I can count on in Winter, and in summer, as it turns out. Obviously my driving habits are different from most people. #1, I hunt, so I drive in the winter on back roads that aren't plowed. AND #2, my job makes me look at property up for tax sale. That means I have to go on those same seasonal highways in all conditions and they're not always pretty. Sadly, the Prius isn't up for the task.

And it isn't me, and it isn't my tires and it isn't my footwear choice. I'd put my winter skills against anyone's. I've been driving in snow all my life (I'm 45 and lived in upstate NY for 44 of those 45) and I have NEVER NEVER NEVER had an accident of any kind in snow, never even slid into a ditch. I've driven AWD, FWD, RWD, high horsepower, pickups, low horsepower, ABS, no ABS, VSC, no VSC, TC, no TC, etc. I know how to drive in the white stuff, and quite enjoy it, actually.

We're still keeping the other Prius, I still like the car, but one shouldn't depend on it in slippery conditions when hills are involved (again, read my post above).

I'm happy to see that they have APPARENTLY fixed the issue on the 2010 Prius. I've seen a video posted on here of a 2010 going up a slippery driveway. The TC on that car allows some wheelspin which is sometimes NECESSARY to get up a slippery hill. The 2008 Prius TC allows none.

Zhe Wiz

 

Traction control on the Gen II is less than optimal. I don't know why we keep debating it. It is particularly bad uphill on gravel roads. Toyota agreed and apparently improved it for the Gen III.

My only additional comment is that the traction control often gets blamed for more than it deserves. Bad tires, impossible conditions, and bad technique are dismissed out of hand, and all traction problems are laid at the feet of Toyota's lousy traction control.

Certainly the Gen II traction control is poor, but it's not the only reason cars get stuck. The show is over here; move on.

Tom

 

Tom,

Consider a a design using torque limiting clutch (one that only slips at high torque) in each half shaft like the one between the ICE and the HSD. That would eliminate the risk to to the drive train under wheel slip conditions. Then implement a REAL traction control using the front brakes (incurs a small MPG cost when activated, but so does tire slippage). This would result in eliminating the acceleration traction problem(s) under discussion.

An alternative solution is to copy the Highlander AWD and drive the rear wheels with yet one more electric motor (and a little extra HV battery capacity). I would love to have an AWD Prius.

JeffD

 

A M E N ! ! ! The closest thing we have is the Ford Escape, but it's on the pricey side, and it's a Ford, an older Ford. I have a feeling the NEXT Escape will be a huge improvement, ala the Fusion and Fiesta.

Hopefully someone will give us an AWD vehicle for a reasonable price that gets more than 40 MPG soon. I'm leasing the Impreza for 3 years hoping something improves by then. It has to doesn't it?

Zhe Wiz

 

I live in a hilly area and in the worsed snow we have had in years I have been one of the few who have been able to get through where many other cars have failed. The one time I got stuck between hills I let the tyres down a little and rocked the steering until I got up the hill. I have a 2005 Prius with wider than stock tyres so it should be worse than most.

 

Prius + snow = Wheeeeeeeee!!!!!!!!!!

I commute 45 miles one way, never had an issue. Use General Altimax Arctics with studs.

 

Great comments by posters.

I changed my tires a week ago to HydroEdge 195 60/R15. Thought I still have to up my PSI to 42/40. They are at 38 cold right now. My journey to office is an up and down road with avg max 40mph slow traffic. The car holds good while in motion and I let other cars kiss my snow dirt. It was today that I experienced the problem trying to move forward after halting uphill. It would not move ahead. After backing up a little it found traction and I was able to go ahead. I admit I was trying to floor the pedal to get some traction without understanding the basics of the cars TCS and after reading the posts I feel enlightened. I will try to stop and start again, uphill, in snow, to see what happens and how effective is my newly acquired knowledge.

Thankyou very much.