I HATE my prius

<div class='quotetop'>QUOTE(Delta Flyer @ Jan 23 2007, 10:50 AM) [snapback]379492[/snapback]</div>

Ok, granted, if something actually grabbed the wheels and prevented them from turning, sure, shut it all down before it burns up. But that's not the issue -- the issue is that the wheels turn too freely, not that they are prevented from turning.

When the wheels spin, Toyota has to limit wheel speed to protect the HSD. I have no problem with that. But my conjecture is that a) they don't have to limit the spin to zero in order to protect the HSD, but instead b) they chose to limit it to zero as the optimal thing to do on smooth wet pavement. It just turns out that's not a very good choice if the wheels are spinning because there's loose crap under the wheels that you'd like to dig out of so you can move the car.

So, I think Toyota could fix this, that's all I'm saying. Don't know that for a fact, just believe they could. ANd based on this and other threads, there are a bunch of people who are either really angry about this, or who view it as a safety hazard and a flaw. If this could be corrected via software, Toyota is generating a lot of ill will for nothing.

It's entirely possible that Toyota weighed the options and decided that the "zero slip" version of TRAC would be safer on average (for the driver, not the HSD). So they never offered a "limited slip" TRAC, as I describe above (allow constant spin up to 10 MPH say). But I think they could and should offer it. I'd gladly trade stock TRAC for a reflash that would allow my "limited-slip" TRAC. Because it'll beat having to find the wheel speed sensors while kneeling in snow or mud.

 

<div class='quotetop'>QUOTE(chogan @ Jan 23 2007, 11:06 AM) [snapback]379508[/snapback]</div>

I think that the very fact this continues to come up indicates some dissatisfaction with this aspect of the car. I mean, parts of it have clearly received a tremendous amount of thought...but for whatever reason, this one didn't. I'd think that any test engineer driving the car in wet conditions might notice...then again, there's not a lot of traffic on those test tracks...

I'd rather the MG's give their last in a funeral pyre of sacrifice, than for me to end up broadsided by a truck.

Yes, I know, I should wait 'till there's a bigger space in oncoming traffic...then again, this is the only car I've driven where I take note of the potential coefficient of friction of the surface upon which the driving wheels are resting (and I live in the CA Bay Area!) before deciding how far I should press the accelerator pedal.

The LSD of some sort would be best, but even torque limiting from 0-5mph would be okay; the car has waaaay too much torque from a standstill, relative to the amount of horsepower one comes to expect from it. Once it's rolling, it's a normal car, but from a standstill, all that electric-motor torque makes far too easy to spin the tires --- worse, the whole process is really difficult to modulate.

This will probably be the single reason why I'd consider selling the car before I normally would (i.e., until it dies from old age).

Recently, I lent the car to a trusted friend and it 'surprised' her, too...and she's about as far from a performance driver as one could be. Honestly, after this incident, I'm not sure she'd want to drive it again! That's just one person's opinion, but I think it's telling, too, that she even felt compelled to mention it.
[sigh]

 

<div class='quotetop'>QUOTE(Delta Flyer @ Jan 23 2007, 10:12 AM) [snapback]379452[/snapback]</div>

I wouldn't think a light pickup truck bed / wheel spinout would have anything to do w/ why no pickups yet ... after all, the front wheel drive gets all the weight ... ok, now back to topic.

 

<div class='quotetop'>QUOTE(chogan @ Jan 23 2007, 11:06 AM) [snapback]379508[/snapback]</div>

Chogan, you're right on track with this one. I have exactly the same take, and this comes from someone with 30 years as an electrical engineer. The traction control could be programmed to provide limited slip without hurting the MGs. Toyota made a deliberate decision about this, but in this case they missed the mark. The good news is that is should be fixable with a firmware upgrade, rather than a redesign of the HSD.

Tom

 

Bryan,

I am interested in your solution as I live west of Boston. Thank God for a mild winter so far.

Thanks...

please send to : [email protected]

Thanks again

<div class='quotetop'>QUOTE(BT Tech @ Jan 21 2007, 03:14 PM) [snapback]378752[/snapback]</div>

 

Please see my post several posts back where I described what I did. I was getting WAY too many PM's.





<div class='quotetop'>QUOTE(BVISAILMAN @ Jan 23 2007, 03:15 PM) [snapback]379599[/snapback]</div>

 

I very confused, the wheels on my 2005 spin on ice even when the traction control kicks in.

We had a minor snow last Friday, only about a 1/2 inch, but my town chose not to salt the roads and after the morning rush hour started, everything turned to glare ice. Cars when in the ditches all over the place.

Well, about 2 miles from home, I had to stop for some traffic that was trying to get around a car that had spun into a ditch. When it was my turn to stop moving, I discovered I was stuck on the ice on a slightly uphill grade.

But here's the thing... my tires were spinning! I could hear it quite plainly and could feel the vibrations. Sometimes the left front tire would spin. Sometimes the right front tire would spin. From the throbbing sound my tires made as the spun on the ice, I'd say they were spinning at about 3 revolutions per second.

By the way, I have Goodyear Comfortreds with less than 2K miles on them.

 

<div class='quotetop'>QUOTE(Marlin @ Jan 23 2007, 01:50 PM) [snapback]379622[/snapback]</div>

Right, this is what I described in an earlier post as the drive train "pulsating". So, to say no slip is an exaggeration. You get a fraction of a second of slip. But I didn't interpet it, when it happened to me, as the tires turning at 3 RPM. I interpreted that as the drive train cutting in and out three (i'd have said two) times a second. But I didn't poke my head out the window and look at it.

But what TRAC won't let you do is spin the wheels continuously, so that you could dig your way out of soft snow, or get the gravel out from under your wheels, or build momentum slowly with the wheels spinning continuously.

Anyway, based on the prior posts, here is what I believe to be the completely accurate statement.

Some earlier models (2004 to mid-2005?) had what I interpret as an error, in that a single triggering of TRAC meant that you had to shift gears or reset the car to get the wheels to turn again, at all. Posters reported having that problem resolve after a reflashing that targeted the known highway stall issue. This may or may not be the problem the OP of this thread (lazyleo) has, as he has a 2004.

For the rest of us, the problem with TRAC is that it will not allow the wheels to keep spinning, even at moderate spin speed. You can spin the wheel until TRAC cuts power and/or brakes the wheel. Then the wheel stops, the car stops, power is reapplied, the wheel slips again, TRAC cuts in again, and so on.

On gravel, this means you get just enough traction to take the nose of the car out into traffic before TRAC stalls you. Which I believe everybody thinks is less than optimal.

On ice, this means that the drive train pulses on and off, until you get to the point where the wheels find some grip. So, if you need, say, 10 seconds of low-speed wheel spin to plow through some slush and get the car away from the curb, you're out of luck.

So, what I wish Toyota would offer would be the option to set TRAC so that it allows continuous but speed-limited wheel spin. For the gravel start, that means you could at least get past the gravel onto the pavement, albeit more slowly than you might like. For snow, it would let you rock the car like a normal car, and spin through loose snow/slush to get down to the pavement beneath.

As an aside, an earlier posted suggested that when the wheels spin, just floor it. Totally contrary to a regular car, but swore that it worked for him. Now I think I understand why. If TRAC allows some fixed fraction of a second before cutting power, then it takes time for the wheel to spin/brake to a stop, you actually will end up with the wheels spinning a larger fraction of the time if you floor it than if you baby it. So, if TRAC works on a fixed timing, then yes, I believe flooring it would certainly get you more tire revolutions, and arguably would keep your wheels spinning a higher fraction of the time. Sounds good in theory. Still don't know if I'd have the moxy to do that, though.

Hey, you Prius owners in snowy states: what happens to the "pulse" rate when you push the gas pedal down while TRAC is cutting the power on and off? Does it pulse at the same rate, or does it pick up the tempo if you give it more gas?

 

lazyleo:

When researching the Prius here on PriusChat and prior to purchasing, I discovered that the OEM tires were just terrible in ice and snow. I made a deal with my Goodyear dealer and he traded the OEM's for new Goodyear Assurance Comfortreds. I can honestly say they have exceeded my expectations in all sorts of driving conditions.

So, I guess I am adding my 2 cents worth to the majority here who suggest you invest in better tires. I would also look into the software upgrade. You make a valid observation that your current situation is unsafe. I believe the majority of the feedback folks have provided here is useful.

Cheers

 

If you'd rather not have to get out and lay on the wet ground
behind a soggy car to get at the wheel speed sensor connectors,
there's always inspection mode. Search for it in the forums.
Same risk, of course. Keep in mind that with the ICE off, MG1
can spin TWELVE times faster than the wheels, and without any
resistance the wheels are not much of a flywheel as far as MG2
is concerned.
.
But in general I would first suspect the loose nut behind the wheel.
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Jan 23 2007, 07:16 PM) [snapback]379771[/snapback]</div>

Thank you, Hobbit. Post 39 in this thread has the instructions for turning off TRAC from the dashboard. I'm going to print the instructions and leave them in the glove compartment. The riskiness of driving without TRAC is duly noted (that I can fry my HSD by driving in this mode).

http://priuschat.com/index.php?showtopic=6...0mode&st=20

It doesn't solve the gravel-in-the-road problem, but it might come in handy when stuck in the snow or mud.

 

<div class='quotetop'>QUOTE(Delta Flyer @ Jan 23 2007, 12:50 PM) [snapback]379492[/snapback]</div>

Hi All,

Delta Flyer is quite correct regarding DC motors with wound rotors. These windings have to be swinging around in the air to be cooled, and there is also no back EMF to limit current when the rotor is stationary. So only the winding resistance which is small, limits current.

When a motor turns it acts like a generator, whether you are feeding it electricty or not. The generate current flows backward from the direction that would make the motor turn forward. The back current creats a voltage when it tries to flow through any loading resistance. Try it sometime. take a toy motor, hook it up to a volt meter and spin.

The motors in the Prius and most professionally designed electric vehicles have fixed windings in the stator. This serves to cool the windings continously whether the motor rotor is turning or not. But if the motor rotor is not turning, there wont be any back emf, and the current in the windings will be greater for a given input voltage.

One would think that the electronics controls on the Prius would sense the back emf and/or winding current and temp, and act to protect the motors. Also, in cold weather the transmission housing is one big hunk of heat sink.

The bigger problem is probably the shock load on the large diameter spinning rotors if the tires should catch something that wont let them slip. The magnets in the rotors are glued into angled slots. Normally the force is radial due to the simple spining motion of the rotor. But if the rotor were to go from 6000 RPM to 0 in a tenth of a second, then there will be considerable tangetial force on the magnets. Which could result in the glue joint cracking, or even a magnet being thrown.

Another problem is that you are spining that large flywheel mg2 and mg1 fast, and then you stop it suddenly. That generates allot of forces in the planetary gears and the chain to the final drive. The tire rubber will act to cushion the shock, but as tires are made lower and lower profile, the radial shock cushioning is less and less. Something might give.

So, while it may be OK to disable TC in the sand. On a snowy road, where there are patches of bare pavement, there is a considerable risk to the motors (let alone the differential - as any Yahoo pickup truck driver will tell you).

 

<div class='quotetop'>QUOTE(chogan @ Jan 23 2007, 07:56 PM) [snapback]379787[/snapback]</div>

Well, pooh. I just tried those instructions, after driving out the store to warm up the engine, and I got nothing. Would some knowledgeable reader care to tell me what the secret handshake is? The instruction say:
Start the car. Let the engine shut down. Within 60 seconds of start:
Floor it twice in Park, twice in Neutral, twice in park.

It should go into inspection mode, but as far as I can tell, nothing happens. Is this too subtle for me to notice?
Can anybody clue me in on what I'm doing wrong?

EDIT:

Got it.

Keep your foot off the brake. Hit start. Wait a bit.
Still keep you foot off the brake. Hit start again.

Now do the dance:
Floor it twice in Park
Shift to neutral (requires a foot on the brake?), floor it twice in Neutral
Put it in park, floor it twice again.

A flashing red icon representing a Prius being run through a bandsaw will appear on the MFD.
Step on the brake and press start again to start the car.
The ICE will not shut off in this mode and TRAC will not function,

Thanks again, Hobbit. Your and others' cautions are duly noted. I believe the bandsaw icon was well chosen for this mode.

 

<div class='quotetop'>QUOTE(chogan @ Jan 23 2007, 06:03 PM) [snapback]379816[/snapback]</div>

That is a great warning icon.
I may have to try it just to see the icon.

Dave M.

 

<div class='quotetop'>QUOTE(Pinto Girl @ Jan 23 2007, 12:10 PM) [snapback]379550[/snapback]</div>

Okay, let me just probe a tad bit into this statement. Do you still own the Pinto? Are you expecting to be less loyal to the Prius than to the Pinto? If so, that is a statement all in itself!

Also, have you or others noted that both of these cars start with the letter P and have 5 letters in their name? Actually, there are other similarities as well. Oh my god! Do I own the Pinto of the 21st century? I can't believe this has happened to me.
Please reassure me that you don't really mean to claim that the Prius is a lesser car than the Pinto.

 

It would be polite if lazyleo would come back, acknowledge the help, and close out the thread.

Barring that I'll concisely summarize the TRAC issue and solutions as I understand them. All credit to the original posters.

1a) Some 2004 and early 2005 Prii have an outright flaw in TRAC operation that results in no movement after TRAC is triggered once. Reflash for the known highway stall issue appears to solve this problem.

1b) Otherwise, if the traction is poor enough, attempted acceleration on ice or snow may result in successive cycles of wheel spin and TRAC intervention to stop the wheels, several times a second. I'd say TRAC "pulses" the drive train.

1c) One poster suggests that the best strategy, to keep moving, is to floor the gas pedal when TRAC intervenes in that type of situation. Other suggestions were typical winter car suggestions (snow tires, traction aids, keep momentum up, don't get stuck in the first place, and so on.)

2) There are at least two ways to disable TRAC. Both of them risk destroying the HSD.
2a) Pull the wires off the rear wheel speed sensors (or permanently put them on a switch). This disables TRAC but otherwise lets the car operate normally. Error lights will show on dash. Plug the wires back in, and within 20 miles the car will return to normal operation.
2b) Engage "inspection mode" as described earlier in this post. This disables TRAC and forces the ICE to run constantly. Flashing red icon will show on MFD. Turn the car off and restart to return to normal operation.

3) Earlier threads on this and other boards have flogged Toyota over the TRAC issue in the Prius. They also raised the issue of having limited wheel spin instead of zero wheel spin as a TRAC setup. Years ago.
3a) I infer from that that Toyota either can't or won't change the TRAC setup to allow limited continuous wheel spin. They certainly know by now that it bugs people.
3b) That means the "starting from a gravel patch" TRAC issue, at this time, appears an inherent problem with the Prius. Unless you a) want to modify the car to cut out the rear wheel sensors as described earlier in this thread, and b) have the presence of mind to turn it off ahead of time. There is no automatic fix.
3c) But the "I'm stuck in 2 inches of snow" issue may be at least partially addressed by turning off TRAC once you are stuck. With completely understanding that doing so may destroy the HSD. I printed the complete directions for turning off TRAC and stuck them in the glovebox with the manual.

4) I had some trouble getting this to work. You have 60 seconds to perform the sequence, from the time you press the start (power) button. For the record, as clearly as I can put it, to turn off TRAC:
a) Begin with the car off.
b) Keep your foot off the brake, press start (power), wait for MFD to come up.
c) Keep your foot off the brake, press start (power) again, wait for dash warning lights to come up.
d) Press the gas pedal to the floor twice while in Park.
e) With foot on brake, shift to Neutral. Verify by looking at shifter symbol on dash. (I have to jog the shifter toward D to get it to go into N.) Press gas pedal twice to the floor whjle in Neutral.
f) Put in park, press gas pedal twice to the floor while in Park.
g) Flashing red icon should appear on MFD.
h) Put foot on brake, press start (power) to start the car.
i) ICE will run constantly in this mode.
j) Drive gently. YOU CAN DESTROY THE HSD BY RUNNING WITH TRAC DISABLED.
k) When done, turn off and restart the car to put TRAC back into normal mode.

Some threads also seem to indicate that you have to let the car go through the normal warmup sequence first, or that the engine can't be running when you do this. I don't know whether that's oriented toward the real use of this mode (for emissions inspections), or whether those conditions would actually prevent you from entering "inspection mode" as above.

Use at your own risk. Every knowledgeable poster has said this is dangerous and could destroy the HSD. I accept no liability in repeating these instructions. They have been posted on this and other boards.

 

<div class='quotetop'>QUOTE(Three60guy @ Jan 23 2007, 01:31 PM) [snapback]379710[/snapback]</div>

I can second that. I'm not disagreeing with the TRAC issue, but the Prius with Comfortreds is quite a snow machine. It went up and down our - unplowed 600+ ft, uphill driveway just fine. It was a little harder as the snow turned to ice because of the TRAC issue, but if I got a running start I could make it up to where it levels out. Still not as good as our old Subaru Legacy, but for a 2WD car, not bad at all. Get your car some new shoes and I think you will be much happier.

 

Tires make a big difference. I was ready to replace my Protege5 with an AWD vehicle because I kept getting stuck in the snow, and couldn't get up my moderately inclined driveway with just a touch of snow on it. But I decided to give winter tires a shot, and they made a huge difference.

But there's definitely a traction control issue here. In a worst case scenario, is it possible to disable it by pulling a fuse? Or would this risk damaging the powertrain somehow?

 

Just as we expected, the ambulance chasers who troll for class action law suits on the ConsumerAffairs.Com website, have jumped on the "Prius is unsafe for road use under any snow or ice conditions" bandwagon:

Prius Shuts Down in the Snow, Reader Complains

 

That's why I am about to trade in mine for a regular AWD sedan. I could not get to work for almost a week.