How to disable VSC?

Remember that your right foot is only a voting member of the whole control system. You have no direct control over MG2. You can, however, say to the control system: "Say, I'd like to go a little faster" and hopefully it will do what you had in mind. The power cutout for traction control is really just a safety valve in the control. If the computer wasn't in the loop, you would need the touch of a safe cracker to keep from spinning the tires.

Tom

 

From a performance perspective, it's best to learn how this car handles in various situations. If you're having a problem with power delivery while pulling out of a driveway, it's best to learn why the Prius does that (TRAC), and how to adjust your driving for it (controlled acceleration). I encounter no problems with any of the safety systems. In fact, I'm a VSC abuser that exploits it regularly.

 

In my view, the electronic safety systems show be as unintrusive as possible. If you have to adapt your way of driving to them, something is not ideal.

The VSC in the prius really got me once, when I was entering a road from a crossection and there was an (invisible) patch of oil on the road. For a few very long seconds, I was standing there halfway the road, without any traction. A good traction control system (such as the one in my volvo), would have braked the slipping wheel first, causing the differential to send power to the other one.

These are the kind of unforeseen situations where electronic safety systems can make a difference, even for resposible drivers. The prius is an excellent car, but imho the traction control system is one of its weakest points.

 

Agreed. Like a sound track in a movie, if properly done, you don't even notice.

A minor quibble, and I know you know the difference, but I'm on a campaign to help people understand the difference: what you describe was traction control, not VSC. VSC comes into play to stabilize the vehicle when maneuvering at speed. The loss of power you experienced was traction control only.

Part of the issue is that Toyota did such a good job with the rest of the design. The the engineering in the Prius is very good, where the traction control system is below average. I would say that the two most common complaints on PC are for traction control and the fuel bladder.

Tom

 

Oops, my fault indeed :doh:.
I ment traction control. The difference is quite important. In fact, I'm on the same campain, so it is a little embarrassing that I used the wrong term myself...

 

Firstly, if you have a newer Prius, disabling traction control will not help you get unstuck in snow. The newer traction control algorithm allows for wheel spin. If you are stuck with traction control, you will most likely be stuck without it.

I have a 2007 and my Prius' wheels NEVER spin (other than at road speed). But, I live in Hawaii and they have never seen snow. However, in grassy mud and gravel, I can put my foot to the floor or feather gently... with the touch of a safe cracker... and they will NOT spin out.

Secondly, without traction control, you will not be able to "gently" attempt to free the car. The low end torque on the Prius is unlike anything any of us has ever driven in terms of ordinary passenger cars. Without electronic speed limiting, MG2 can instantly over-spin the drive wheels.

First, you are giving the Prius' electric motor WAY more credit than it deserves for torque. Though it has an impressive-looking number of over 200 lb-ft, the battery's super low capacity just won't deliver. Plus, if you hit the Prius' accelerator pedal even more than just a hair off the line, the ICE kicks in, and that limits the electric motor. If the Prius TRULY delivered that kind of torque, flooring it from a standstill would not be as uneventful as it is in real life. Try driving your Prius ONLY in electric mode by pedal control. You have to keep the pedal BARELY pressed or the ICE kicks in. Face even a SLIGHT incline and the ICE kicks in. If I don't time entering my driveway properly, I'll get hung up on it's lip and the electric motor can't even get it over the lip. I have to LITERALLY floor it to kick in the ICE to get over my road-to-driveway curb lip. And my driveway is hardly steep. The Prius' electric motor is NO monster, that's for sure.

If the speed limiting thing IS true, brake-assisted (as opposed to engine shut-off) TRAC/VSC would remedy the problem without leaving you literally a powerless sitting duck. So would an electric motor rev/acceleration limiter. Sorry, but shutting off all power is TREMENDOUSLY dangerous and simply unforgivable.

There are really three issues behind needing speed limiting traction control with HSD: 1) Control. Without it, most of us would burn off our tires even on dry pavement (well maybe not, but there would be a lot of squealing and burning out);

I REALLY doubt it! The combined total of the HSD system is only about 117 hp or so. Torque doesn't burn rubber, hp does. And the Prius won't rev up enough to generate the rated hp. And even the rated combined hp isn't enough to do anything more than spin 'em for a second at the most.

The combined power of 2) Over-speed. It is very easy to over-speed parts of the HSD without speed control. In a low traction situation, you could easily over-speed MG1 even with the engine running. MG2 can change speed much too fast for the speed of the ICE to catch up. The damage would be done before the control system could do anything about it. Still, you could spin your tires in snow at a rate equal to about 60 mph without damaging MG1, so that's not the key issue unless you drive like an idiot; 3) Shock loading. If you spin up the drive train, then hit a dry patch, the shock loads are increadible. Limiting wheel speed limits the potential for shock loading.

The real issue comes down to traction. If you have good traction, then traction control is not a problem. If you don't, then you end up posting in a thread like this.

I started this thread and I live in Hawaii. We NEVER have snow here. All my complaints are on dry paved surfaces with LOTS of traction. My gripe is that this thing shuts off power while just driving over patched up pavement. Anything that can bounce the wheels even minutely, and I mean MINUTELY, will kill your propulsion. A TINY gravel patch in a turn? Power shuts off for a second, and AFTER you're past the gravel... The BIG gripe I have is that transitioning from differently angled surfaces (turning right from a parking lot exit sloping downward to a street sloping downward to the right) that can possibly cause a wheel to lift off the ground will kill the power. This happened to me twice at a particular driveway and I came damn close to getting T-boned.

Tires are a key element. The Goodyear (lack of) Integrty tires are not a good winter tire (I don't think they are a good summer tire either, but that's another discussion). Without good tires, disabling traction control will just produce more wheel spin.

I have had 215/45/17 BFG G-Force Sport tires since mile 97. They are quite sticky tires. WAY WAY more sticky than stock! And they ONLY see snow-free, mud-free paved road.

In rare cases wheel spin can be used to move on ice and snow when you are able to burn down through the surface to something substantial. Generally this doesn't work in real winter conditions.

Real traction control, unlike the speed limiter on the Prius, provides a means to improve traction. Generally real traction control engages the brake on a spinning wheel to force driving power to the other wheel. It acts as form of limited slip, which actually improves your chances of getting up a hill. The Prius system doesn't improve traction, it just keeps you from spinning uncontrollably, which is useful, but not overly effective except in the sense that it prevents damage to the HSD. While the Prius traction control system doesn't help much, it doesn't hurt much either.

It's not useful. It's total rubbish. It doesn't do anything that taking your foot off the pedal won't accomplish. If you're not a retard and can figure out that if you're stuck, the answer is not flooring it, you will outperform the Prius' TRAC everytime. And I disagree. TRAC/VSC DOES hurt! It has put me into oncoming traffic and could have CAUSED a head-on crash. Luckily there was no car in that lane at the time! And, as previously mentioned, it almost got me T-boned. These aren't little quirks, this is life-threatening.

Generally people blame traction control for a low traction situation in which they wouldn't move with or without traction control. It's a lot like the comments we see about VSC causing a driver to lose control and nearly kill themselves. Generally what happens is the driver loses control and VSC kicks in and tries to save him, but the driver sees it the other way around. Perception is a tricky thing, and when people get a notion in their heads it's hard to shake it out with logic and reason.

Again, I totally disagree. Having race experience on motorcycles, front and rear-drive cars and a lot of off-roading fooling around in my Jeep, I find ALL forms of "assistance" a hinderance. Except MAYBE ABS... and I'm not really much of a fan of ABS. And that even includes Porsche's PASM. I have a Porsche without assists and FAR prefer it to Porsches with assists. Assists interrupt the car's dynamics. They kick in long before trouble happens and by doing so cause their own trouble! You see, I've already calculated what it's going to take to get through a turn. I KNOW how the car's going to move. If the car takes any power away from me, it is effectively throwing me INTO the turn. And maybe into a tree or guard rail or something. If the car makes ANY "corrections," then I will have to rethink and recalculate everything. And I will have to do so predicting that other automobile calculations will not mess me up further. That is NOT "attempting to save me when I'm out of control, but it's too late." Keep in mind, the Prius' TRAC/VSC is certainly not a Lancer Evo 10's or a Ferrari F430's version. The Prius certainly has no fine nuances and stepless compensation. It has ONE mode: kill power for a second.

It's really too bad that such an otherwise cool car has to have this death machine flaw...

 

Not spin out, just spin. They can and will, but at a very slow and controlled speed. I couldn't tell they were spinning from inside of the car, but only by noticing that I could track back and forth across a slippery hill, just as I used to do with my Jeep.

Keep in mind that I am not defending or praising the traction control on the Prius. It can be very frustrating, especially with gravel.

MG2 has plenty of low speed torque, and the traction battery has plenty of power to make it go for a short burst. Torque is limited by the control system to protect the electronics, drive system, and battery. ICE turn-on is controlled in such a manner as to optimize its use, and also to contribute to the total available power. At low speeds (not low RPMs), most of the torque and power is transfered through MG1 and MG2. What you see as limited torque and power is what Toyota has decided that they can safely give us with the existing system and limits of driver safety.

Where do I even start with this one? I don't really want to do an introductory class on physics, but maybe we can just hit a few points:

1) 117 hp is a little over 87,000 watts of power. That's as much as 87 microwave ovens all at the same time - certainly more than enough to burn some rubber.

2) It takes power to spin tires against friction, but the power must come with enough torque to overcome the friction. In this example, friction, torque, and power are all interrelated. The phrase "Torque doesn't burn rubber, hp does" is meaningless.

Bouncing will do that, and I can't say that I disagree with your complaint. The torque limiting is there to protect the HSD from shock load, which you get with bouncing, but there should be a better way - either a more robust HSD or better traction control.

I assume that a driver with your skill and experience has adjusted to avoid these situations. Those of us that frequently drive in low traction situations learn to look for problems before pulling into traffic, whether driving a Prius or any other car. When you know a car has limitations, you learn to drive within them. I assume you do that.

You must be one of the rare exceptions, where your experience, training, and reflexes allow you to out perform the computer. Some people are able to do this, depending, of course, on how good the automated systems are. We used to see a lot of this with airplanes, where pilots were very suspicious of fly-by-wire systems. It may have been true with early fly-by-wire, but now many aircraft are unflyable without computer support. Most automobiles are still a long way from this extream, but you can expect future control systems to out perform even experienced drivers.

Part of the problem comes from expectations and design goals. For a normal passenger car, engineers design to maximize safety. For a race car, you might trade off safety for more performance. In the case of the Prius traction control, it appears that the designers favored protecting the drive system at the expense of drivability. Hopefully this will be better on the new model.

As a final note, it's a lot easier to reply to these long posts when people use the standard quoting blocks.

Tom

 

Qb, I'm guessing you don't have a lot of experience TRYING to burn out in cars.

The Prius has about the same total hp as a 1.8 liter 4 cylinder Honda Civic. But a claimed torque output higher than a 4 cylinder Toyota Tacoma. And I don't care if that's 1.21 JIGAwatts, Doc Brown... 117 hp is not enough to burn a respectable amount of rubber if that rubber is a tire attached to a car's drivetrain. It takes 500+ hp to lay down a real tire track without cheating with braking or holding the car in place one way or another. Face it, stock Civics ain't exactly burnout kings... So, you can put yer physics in yer pipe and smoke 'em and let a Dodge Viper smoke the tires...

"Torque doesn't burn rubber, hp does" is NOT a meaningless statement. If you understood cars, you'd know that torque bands are in the low RPM range. It's essentially pulling power. While IN the torque band, tires just don't spin fast. So you won't be "burning" them (unless the vehicle is HELD stationary). You MIGHT break traction, but that's about it. It takes the high engine RPMs in the hp range to really spin tires.

Now, if you want to get into a semantic debate about the actual force required to break traction with enough force so as to melt a tire, I'm not interested. Corvettes smoking tires until they explode and Hummer H1s barely being able to break traction is a great illustration of monster hp smokin' 'em and monster torque just moving mass around.

Now, to get that 100+ hp out of the Civic or the Prius, you'll have to be pretty near redline. So, you have to either "neutral drop" it or pop the clutch from near or at redline. Well, that's just not possible with the Prius so smoking the tires is simply impossible. And even popping the clutch in a Civic doesn't yield much of a burnout at all. Name one time you saw a stock Civic "burn out" and you didn't laugh. I sure can't.

Look, my gripe with the Prius' TRAC/VSC is that it responds when it shouldn't. In often REALLY dangerous ways. I'm just driving like I would any normal car under regular circumstances when all of a sudden, BAM, the Prius throws me a frigging curve ball! And it DOES take my driving experience to CORRECT it's horriffic errors. Not to toot my own horn, but average drivers could find themselves dead because of these stupid activations. Even I could. And almost did once. Good thing that other driver was paying attention as I gently coasted almost motionless sticking halfway into the road from the driveway! And it's a REALLY good thing the other time that there was nobody in the oncoming lane that I got thrown into!

Yeah, Toyota is protecting the sensitive drivetrain (maybe) with it's "assists." And the only expense... might be your life. Or constant inconveniencing. And I don't even encounter snow or mud or dirt or gravel roads... I really pity you guys in those conditions!

 

Oh yeah, and about MG2 having plenty of torque... Then why can't I even get up my driveway curb without flooring it to kick in the ICE? My Honda Ridgeline has barely more torque than than the Prius claims, but my gas pedal, under the same circumstances, doesn't get much action at all A little tap and it's all good...

The fact of the matter is that even to access the torque in the electric motor, you DO need SOME electric motor RPM. From a standstill, the Prius has NO power. Place any demand on it and the ICE comes on.

So sad. On such a cool car.

 

Oh bull plop, I call total bull plop.
I had a Mazda RX2 which had about 200 ponies at the back wheels and it would smoke the 225R - 13 Yokohama A008 tyres until they were a sticky mess. The key was torque multiplication, it had a 4.4:1 final drive ratio and would rev to 8,000 RPM with the wheels spinning.

The reason the Prius doesn't leap off the line blazing the tyres in the dry is MG2 is always in top gear. Think about it, MG2 has no torque multiplying low gear ratios to get the tyres howling. In fact MG2 is like the output shaft of a regular transmission prior to the power going through the final drive. That's how HSD works, it uses the high speed input to MG1 to generate electricity which is fed into MG2 along with power from the traction battery and some torque reaction force from the ICE to give similar torque to the final drive that a 2 litres car would through a conventional automatic transmission.

 

I'm just about done with this debate. There is an old saying that says "Never try to teach a pig to sing. It only wastes your time and annoys the pig." I don't mean to imply that you are a pig, but only that I am wasting my time, and it appears that I am annoying you. Perhaps another poster wants to take a crack at explaining the physics.

In relation to "burning out", the maximum hp developed by an engine is meaningless if it can't be coupled to the tire as low end torque. I could take a spring wound clock motor and pull your 500 hp monster backward if the clock motor is properly geared. My old 150 hp Jeep C-J5 was able to spin its tires in 4wd on dry pavement. It's easy to do with the right gearing. With an electric motor you don't need the gearing. Granted, the Prius lacks the power to do a sustained burn out where you go squealing down the street, but that's not the issue here (at least not my issue).

Once again, I'm not talking about "burning out", I'm talking about breaking traction at low speed and causing the drive wheels to spin. I'm sorry if my use of an exaggerated figure of speech has caused you confusion and concern.

Tom

 

Oink oink, I'm not annoyed at all.

Pat, I used to run Yoko A008R also. About 20 years ago in my 1978 Scirocco with a blueprinted 1984 GTI motor. Those were some damn good tires, though they didn't last long at all. MAYBE 3000-5000 miles. I believe I was running the 215s. I had about 165 hp and she was a front drive, of course. I could barely break those tires loose at all. The only way they would let go was if I hit a turn way hard and/or fast. In fact, I took down a Ferrari 308 Quattrovalvole with that car when I was 18 around my favorite mountain road despite being WAY underpowered for that impromptu race.

So you could smoke that rubber to a mess, eh? Were you braking? Doing controlled donuts? because that's different. That's "cheating." I'd be shocked if you could just smoke them off the line and lay tracks in a 200 hp car. Particularly with such sticky rubber. I daresay... it defies physics...

 

This whole thread really starts to have a touch of surrealism... I mean, talking about doing burnouts with a prius! :roll:

Torque is a dangerous thing to talk about, much more subtle than power. Power a value that is (more or less) conserved over a gear box, torque not at all. That makes the statement "the prius has 400Nm torque" meaningless and misleading if you compare that value to a conventional car. There is no reduction box between the torque of the main electric motor and the wheels.

Nothing illustrates that better again than the comparison between the D5 diesel engine of my XC70 and my prius. Incidentally, both are specified to have exactly 400Nm. But the is a tremendous difference in torque on the wheels (which is the only thing that matters when it comes to pulling something). In EV mode (my prius can do that), the prius can barely start itself on a light uphill, regardless the 400Nm. In contrast, my XC70 can easily depart with a heavy trailer on a steep hill. Because of the reduction in low gear, there is much more torque on the wheels (maybe something like 4x more).

 

Yup.

 

When I compare the TC system of my 2004 Prius to my 2007 FJ Cruiser, that is the most obvious difference. Although some claim the Prius will also apply a brake to the wheel without traction, that is simply not true

I doubt this has anything to do with the Prius being front wheel drive, as many front wheel drive cars with TC will apply the brake to the wheel without traction. My FJ is a part-time four wheel drive, not an all wheel drive. It normally is a rear wheel drive vehicle.

A common scenario here in winter is at an intersection. The road next to the curb will typically have ice, and at -25 C and colder, road salt no longer works. Intersections can have icy edges for a long time

With "all season" or studless winter tires, my Prius would struggle at such an intersection. Light turns green, and the Prius will simply refuse to move. With aggressive studded winter tires, my Prius will move just fine

In the same scenario, my FJ will apply the brake to the wheel that is trying to spin. The wheel on dry pavement will easily move the vehicle. If I put my foot into it, the wheel on dry pavement will squeal. If I *really* put my foot into it, eg 1/3 pedal to 1/2 pedal, the FJ will reduce engine torque

Toyota appears to have learned from the Prius, as some features - electric brake boost - are found on my FJ

As far as torque, I have driven EU market turbodiesel Volvo Estate cars, standard shift, and they are *very* torquey

 

Tom

A modern fly-by-wire aircraft will typically have three modes

1. Normal Law: covers Ground Mode, Flight Mode, and Flare Mode, has three axis protection. This is with no degradation caused by failures, the Flight Augmentation Computers are in. In Normal Mode, on the hsi you will still see "bugs" or carots that define the safe and expected normal bank angle. I've attached a photo to illustrate how this looks. You will notice the "barber pole" forbidden zones for airspeed

You can hand fly the aircraft, eg A320, near this limit. Once you approach that bank angle limit, you must hold constant pressure on the sidestick to keep it at the bank angle limit

There is angle of attack protection too, this is called Alpha Floor protection. If you purposely put the aircraft into an angle of attack that will cause a stall, the aircraft will refuse to operate in this mode, and will set TOGA thrust to keep the aircraft out of danger

That Air France Airbus demonstrator crash was heralded by many "experts" as "proof" the computer took control of the aircraft, causing the crash. Actually, the aircraft refused to let the pilot do that low, slow flyby for the crowd. So he dumped the FAC's, did his low, slow flyby, and stalled the aircraft

It's bulls*** to state the computer "always" controls the aircraft. The pilot can dump the systems anytime he/she choses, put the aircraft into Direct Law, and hand fly the aircraft. Proper training is ESSENTIAL to understand what the system does, how to enter modes, and how to exit modes

Eg: autoflight engaged. Click twice the A/P button on the sidestick. First click turns on the Master Caution wailer, the auto throttle has been disconnected. The second click turns on the Master Warning wailer, the autopilot is now disconnected

The Air Inter crash in France was caused by failure to understand what mode the autoflight was in. The same control knob has two functions: FPA (Flight Path Angle) and F/S (Feet per Second). Say you select a usual -3.3 degree FPA in preparation for landing. The small separate display will indicate "-3.3" and "fpa" in very small script

If you're in the wrong mode, the separate display will indicate "33." Notice the decimal point is missing. In very small script, you will see "f/s." You have actually commanded the airplane to descend at 3,300 feet per second

2. Alternate Law: limited speed protection and yaw protection. In this mode, there have been some failures. It is possible to stall the aircraft, as Alpha Floor is dumped

If still available, the aircraft will warn the pilot about dangerous AOA, speed, etc, with a Master Warning wailer, but there is no protection from most events

3. Direct Law: pilot has "full" control. There is no autotrim, no Alpha Floor, no speed protection. Warning are still aural and displayed, if those systems are still available.

The Canadian Airbus that turned into a glider proved the aircraft was still managable. Air Transat Airbus A330 was flying from Toronto to Lisbon but ran out of fuel over the Atlantic, automatically reverting to Direct Law once the engines spooled down.

The Airbus 330 managed to glide 20 minutes before making an emergency landing in the Azores. Due to Direct Law, no antiskid was available, so all the tires were ruined on landing.

I'd like to know if an "old fashioned" airplane would have done better. How about nice "old fashioned" airliners that stalled on takeoff, due to the crew receiving a stick shaker and stick pusher about a stall?

They didn't think the warning was "real" so dumped the stick pusher, the nose came up, the aircraft stalled, and crashed. How about forgetting to turn on engine probe heat in heavy snow before takeoff? So the EPR displayed an abnormally high value, when in fact they didn't have more than 50% of needed takeoff thrust

Overall, I much prefer a well engineered modern flight envelope protection

jay

 

Actually, an electric motor has 100% torque available at 0 RPM

The reason for what is perceived to be lack of "power" on M/G alone has to do with the software programming for running in that mode, and the fact there is no steep gear reduction like with a conventional stick shift or automatic transmission car

I agree. My first winter with my '04, before my backordered winter tires arrived, I actually came to a stop in the middle of Bishop Grandin and Waverly. The car simply refused to move, no matter what I did. I know how to drive in winter, the car just didn't want to

At that point, I was ready to set fire to the car and the dealership. Almost got creamed by a semi too. With studded tires, no problem, but that doesn't help all year round

I also managed to come to a stop on a steep gravel hill on my way to a company-sponsored fishing vacation. The co-worker with the Lexus RX had no trouble. The co-worker with the VW Golf TDI stick shift had no trouble even after stopping behind me, forced to back up a bit, and go around me with minor wheelspin

In the end, the co-worker with the RX had to help. I put the emergency toweye in the front bumper, and he pulled me up.

When I compare a "real" TC system on my FJ Cruiser, to my Prius, the drawbacks of the Prius implementation are very apparent

I did have a chance to testdrive a 2008 Prius this Spring, when there was still a bit of snow around. That Prius had much better TC behavior, but it's still not perfect

 

Oh yes, it would be cheating by that definition. That was low low speed (or zero speed) attached to something heavy spinning tires because the Jeep didn't weigh enough to use all of its torque type of spinning. All it did was make the Jeep hop up and down while slowly grinding away the tires. It was burning away the tires and leaving rubber on the pavement, but it wouldn't have impressed any drag racing enthusiasts.

Another unconventional way I have seen people burn tires is on ice and snow. They lose traction and try to go by spinning the tires at high speed. The car isn't going anywhere because of the lack of traction, so you would expect very little heat build up. What happens is that a narrow band in the center of the tire makes good contact with the road, while the bulk of the tread slips. The narrow band burns. It leaves an odd appearance with one thin burned ring around an otherwise good tire.

As for burning tires to a smoking mess, or leaving a trail of smoldering goo, you are absolutely correct. There is no way I could do that with my 150 hp. I could get a pretty good squeal, but that's about it. As you have pointed out, that sort of smoking requires torque AND power. You need enough torque to break traction and the power to keep the tires spinning. As the speed of the vehicle increases, the amount of required power increases. Power is work over time. Work is force times distance. With speed, you increase the distance or decrease the time, depending on how you look at it, which means more power. With more hp you can burn the tires at a higher speed. Likewise, if the gearing is correct, you can generate more torque with more hp.

MG2 gives the Prius substantial low end torque. Without a good control system, the Prius would be very touchy starting from a dead stop. It would be easy to cause the drive tires to slip and spin, which isn't exactly conducive to good driving. That said, probably a bigger issue is the strength of the drive line and motor components. The Prius isn't exactly build like a dragster or tractor. It lacks the mechanical strength to use all of that low end torque.

Electric motors like MG2 have two interesting characteristics that differ from internal combustion engines: 1) They develop full torque at zero RPM, and 2) They accelerate very quickly. The low mass and lack of drag allows an electric motor to reach obscene speeds in the blink of an eye. Some types of electric motors will do this to such a degree that they will literally explode if removed from a load, flying apart from the inertial forces of rotation.

How does this apply to the Prius? It means that the designers of the Prius had to worry about over-speed, torque, and shock loading of the drive components. Without electronic control of the electric motors, this scenario is not only possible but probable: A Prius driver steps on the gas to pull out of a side road. The low end torque of MG2 causes one of the driven tires to slip, breaking traction. Before the driver can respond, the torque and acceleration characteristics of MG2 cause the tire to spin at high speed. In the best case scenario, the driver comes off the gas before anything bad happens, other than a little premature wear on the tire. There are two worst case scenarios: In the first, the tire spins so fast that MG1 over-speeds. MG1 over-speed is normally prevented by counter spinning the ICE, but it takes way too long to do that in this case. The second worst case scenario involves shock loading: The spinning drive tire finally catches. Now we have a fast and powerful MG2 twisting on one end of the drive system and a nearly stationary tire on the other. Bad things happen to the HSD.

This is why the Prius traction control system backs off on the power at the first sign of slippage. From the driver's standpoint it's sub-optimal. From the engineers standpoint it is an effective way of protecting the drive system.

Can Toyota do better with this? I'm sure they can. They have improved it from the earlier models, and I assume it will be even better on the next model. If they don't do better, then the future of HSD is limited. Most of us are willing to put up with a few quirks since we understand that the Prius is a new and revolutionary car. As enthusiasts we learn to adapt, but you can't expect ordinary drivers to do so.

It's much like the old Jeeps. I used to drive a Jeep C-J5. The thing had terrible handling characteristics. It had a short wheelbase, a narrow track, and a high center of gravity. It was a rollover waiting to happen. I never had any trouble with it because I understood what I was driving. When Jeep started selling C-J5s to soccer moms all that changed. Jeeps are now more car-like in their handling. Ordinary drivers rightfully expect their daily driver to drive like a normal car. The same is true for hybrids.

Tom

 

On the subject of vehicle control systems, this came in my inbox this morning

Unmanned ground vehicle achieves 90+ mph with Kairos Autonomi system - Military & Aerospace Electronics

A lot of folks don't realize how close we are to having vehicles that drive themselves. Despite what a few self-professed "experts" say, the sack of protein behind the wheel is responsible for the vast majority of crashes

IMHO there is no such thing as an "accident." They are so few and far between, statistically shouldn't even be counted. Aggressive driving is killing a lot of folks

Then we have these nuts in a ricer, who have seen "Fast and Furious Tokyo Drift" a few times too many, and think they can drive in real life that way. I'd be willing to take care of that problem, is somebody is willing to put me in one of these vehicles:

http://www.dillonaero.com/docs/DillonTacticalVehicle-1.wmv

I would expect full indemnification from what I do with that vehicle, and I would also expect to be 100% covered for ammo costs

 

You really have to understand your car's strong and weak points, and learn to live with them or compensate for them, I think. The first time we lost traction in the Prius coming up our (steep) hill was in under an inch of snow. I was very aggrevated, and concerned about what the winter had in store for us. I was planning on Nokian snow tires anyway, and they've made quite a difference in bad weather. Now, on the same hill, in 2-3 inches of packed snow, the TRAC works more-or-less as it was designed, I think. I still fear getting to a point where the car will stop, but we're learning to live with it.

That said, I'll take my Jetta when the weather is bad for a few reasons. One, it has 182k on it and I'll be a little less upset if something happens to it. Two, it's a standard, and while I understand what the B-mode is supposed to do, I don't feel like it's really successful. The diesel allows me to idle in 1st on a flat or downhill surface, and I can descend said steep hill very effectively in 1st gear with no go pedal. B-mode doesn't slow the car enough, and it leads to using: Three, and the most disturbing, is the ABS.

I (now) completely understand the need for the TRAC and VSC in the protection efforts of the drivetrain, but what that also does (and what I haven't seen discussed in this post) is make the ABS incredibly clunky. The ABS response is by far my biggest peeve about this car. The pulses are waaaay too far apart, and that could very well be the most dangerous winter aspect of the car. It really is a night and day difference from the Jetta. While I'm sure it will do it's job in a straight line, I'm concerned about the ability to handle if it engages in a turn. As such, this is strictly a secondary car in bad weather.

I know ABS is different on every car, and the Jetta may be particularly good (I know it was better than the Volvo which the Prius replaced) but I would sincerely hope, as mentioned above, that Toyota can drastically improve the TRAC/VSC/ABS system in the 2010 version. The pulse time has to come down...and that would eliminate a lot of the issues discussed in this post, I think.