Runaway Car

[Illum]

Oh, I normally just drop in all the cooling rods, that usually stops any runaways in the 74's Lincoln's nuclear reactor.

there are simpler approaches, replace the reactor mount with explosive bolts so it can be jettisoned in a hurry and ignite those reverse thrusters:laughing:

 

[turbodog]

...Back on topic, can't you guys wait until Drive by wire steering and brakes come out...

What do mean when? 2 of our 3 vehicles have that right now. Wife's accord has EBD braking. It will brake one of more wheels to help in a normal turn, even when brakes are not applied by the driver at all. This appears to be the culprit that's making all the 07(?)+ accords go through a set of rear brake pads at 15-20k miles.

My s2000 has electric power steering. While not drive by wire (yet) I can tell you it's a lot different than normal power steering.

 

[SFG2Lman]

every electrical component added is just another place point of failure for the vehicle...mechanical everything can be replaced/repaired easily by a common man, and it usually doesn't fail as catastrophically as electrical components, not to mention, you usually get a little warning. (grinding, whining, poor performance, etc) but each electronic brain has thousands of components stamped on layers of silicon at + or - 5-10% accuracy....i love my flashlights, but keep that crud outta my vehicles...i know electronic circuits well enough to know that 5-10 years is max before something on them gives out...and when i buy a vehicle i want it to last longer than that!

(my truck is a stick shift, 2 wheel drive, manual windows and manual locks, and its an 07...you CAN find them i promise)

 

[Mjolnir]

Circuits may "give out" in 5-10 years, but any computer control system can easily have issues well before then (take any version of windows as an example of this). I agree that you do not want an essential function on a car (like the brakes) controlled by something that was not fully tested. However, you can make something computer controlled work well. Just look at any fighter plane in existence today... They are all fly by wire, and they don't often crash because of computer issues or have "runaway acceleration..."

 

[SFG2Lman]

Circuits may "give out" in 5-10 years, but any computer control system can easily have issues well before then (take any version of windows as an example of this). I agree that you do not want an essential function on a car (like the brakes) controlled by something that was not fully tested. However, you can make something computer controlled work well. Just look at any fighter plane in existence today... They are all fly by wire, and they don't often crash because of computer issues or have "runaway acceleration..."

true but they also have hundreds of thousands of man-hours worth of maintenance, those things don't go up without extensive checks, whereas most people don't even look to see if their tires are flat before driving.

 

[Mjolnir]

true but they also have hundreds of thousands of man-hours worth of maintenance, those things don't go up without extensive checks, whereas most people don't even look to see if their tires are flat before driving.

That is also true. I am not saying that it is necessarily the best idea for cars, but that it is possible. I think the best thing would be as much redundancy as possible, and fail-safes to prevent glitches from causing any damage.

 

[buickid]

Some newer cars have electronic parking brakes. A motor actuates the brake shoes when you pull the lever. I've heard about this mainly in European cars, though it could have made its way into other cars by now...

 

[2xTrinity]

As has been stated by at least two others, this is a supremely logical idea. The only potential fly in the ointment is whether the Prius' (or this Lexus') electric motor goes through the transmission or is more directly coupled to the drive axle. Some purely electric cars have the drive motors mounted on each wheel. This seems awkward (at best) for a hybrid. Does anyone know how these hybrid drivetrains work?

This may be taking the thread a bit off topic, but the way the Toyota hybrid transmission the two motors are integral to the transmission -- I've linked to a Java applet that shows a demo of how the transmission works if you're interested:

http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html

Basically, instead of "shifting gears", the engine and two motors are all connected to the wheels at the same time using a planetary gearset. The transmission works by using one of the two electric motors as a generator, then using that electrical power to simultaneously drive the other motor. Power can be stored or withdrawn from the batteries, but it is not necessary for the vehicle to operate. Since the motors all are connected at different gear ratios, this has the effect of 'changing gears'.

An active role by at least one of the motors is required, from what I understand, for any power from the engine to be transferred to the wheels. In "neutral" both electrical motors would simply freewheel from what I understand.

The fact that the vehicle acts as a hybrid does require a lot of redundant systems. Power steering and braking on most cars is dependent on the engine being ON at all times. In the Prius and other hybrid cars the engine can actually be OFF for extended periods of time, it is necessary to have both electric power steerinng, and an auxiliary electric vacuum pump to maintain intake manifold vacuum for power braking. Some (but not all) hybrids also have a second starter motor, in addition to the traction motor.

Back on topic, can't you guys wait until Drive by wire steering and brakes come out:duck:?

What do mean when? 2 of our 3 vehicles have that right now. Wife's accord has EBD braking. It will brake one of more wheels to help in a normal turn, even when brakes are not applied by the driver at all. This appears to be the culprit that's making all the 07(?)+ accords go through a set of rear brake pads at 15-20k miles.

My s2000 has electric power steering. While not drive by wire (yet) I can tell you it's a lot different than normal power steering.

From what I understand nearly all the current braking and steerinng systems are power assisted, and that those assist systems are often governed by wire -- such as cars with features that determine that a driver is too "stupid" to stop in time to avoid a collision, thus applying stronger brake pressure to prevent a crash.

However, all still have a direct mechanical link, at least on some level. Braking without brake assist is for example much much more diifficult, but still possible (in theory) in the event of say an engine stall causing brake assist vacuum to dry up. Also, most cars still can be steered but with much greater effort if power steering cuts out because a mechanical link exists between the steering column and the actual steering on the vehicle. Just as there is a physical cable still connecting the brake pedal to the brake cylinder. It's just that most cars have auxiliary systems to "help" in those cases.

In the case of throttle, the throttle pedal is strictly an electronic input. I am okay with that in the case of acceleration, I would not feel comfortable driving a car in which the sterring wheel and brake pedal were mere electrnic inputs that were mechanically decouppled from the actual steering and braking systems. IMO there should always be some mechanical link between brakes, and steering as a failsafe -- as in the case of a catastrophic failure, it is critical that the driver be able to stop and steer the car, even if those systems are assisted by complex "smart" systems under normal circumstances.

 

[3000k]

while it may be covered on tests, I'm increasingly seeing people not touching the stick except for reverse and park. I drive an automatic, but I always shift it into Neutral at red lights and if I'm carrying something, I tend to use D3 or 2 to accelerate before going into D...I'm not sure where the habit comes from, but I've never driven a manual. :nana:

Illum, shifting into neutral at every light will wear out your linkages, but nothing to worry about, it is cheap to fix. However starting off in D2 or D3 is a TERRIBLE IDEA especially if you are carrying a heavy load. ONLY start of in D2 if you need extra traction on ice, snow, or wet road. In an automatic transmission there is a wet clutch pack for every gear, typically as you go higher in gear, the clutch packs get smaller and can't handle as much torque. In D3 the torque converter will multiply the torque fom the motor, so starting from a stop will most likely cause the clutch pack to slip and burn up. This is why it is bad to tow in OD. If you want your poor transmission to last BREAK YOUR HABBIT!


On another note I drive Ford Ranger which has a mechanical linkage and have had my throttle stuck twice. The first time was because the hood release cable caught the top of the pedal (major design flaw) after I floored it. My engine over powers my brakes, I could not go less than 40mph so I turned the engine off and came to a stop.

The second time was because the cruise control crapped out. I was cruising on the highway and my truck was struck by lightning at the top of a hill, the lightning stuck the antennea and shorted out my radio and cruise control which was currently on. The cruise control motor pegged the throttle wide open. I had some fun took a while to think of the best thing to do and when I reached 110 mph I finally hit the brakes slowing to 65mph and shut the truck off, then cut the CC cable. (the speed limiter in my truck is removed and it can likely reach speeds of 140 or whenever my firestone tires blow)

On a side note, shifting the truck into neutral will do nothing at wide open throttle, the transmission will not manually shift out of drive if there is alot of torque operating on it. Also turning the engine off will cause you to immediatlely loose power stearing. Power brakes are not immediatly affected, vacuum pressure will still remain in the brake booster as long as you don't repeatedly pump the brakes, just push the brake pedal all the way down once and hold it there when you shut off the motor.

 

[Norm]

I would not feel comfortable driving a car in which the sterring wheel and brake pedal were mere electrnic inputs that were mechanically decouppled from the actual steering and braking systems. IMO there should always be some mechanical link between brakes, and steering as a failsafe -- as in the case of a catastrophic failure, it is critical that the driver be able to stop and steer the car, even if those systems are assisted by complex "smart" systems under normal circumstances.

Flown on a modern aircraft lately?

 

[buickid]

Illum, shifting into neutral at every light will wear out your linkages, but nothing to worry about, it is cheap to fix. However starting off in D2 or D3 is a TERRIBLE IDEA especially if you are carrying a heavy load. ONLY start of in D2 if you need extra traction on ice, snow, or wet road. In an automatic transmission there is a wet clutch pack for every gear, typically as you go higher in gear, the clutch packs get smaller and can't handle as much torque. In D3 the torque converter will multiply the torque fom the motor, so starting from a stop will most likely cause the clutch pack to slip and burn up. This is why it is bad to tow in OD. If you want your poor transmission to last BREAK YOUR HABBIT!

IMHO, shifting into the Neutral at every light is worse for the trans. When going back into gear from Neutral, the clutch packs re-engage the planetary gears, during which they are slipping for a short period of time. Same thing happens with each shift, but in this case the planetaries are at a stand still with no chance for RPM-matching, as would happen when the car is in motion. Probably not a whole lot of extra wear, but its better just to leave it in gear at a light, as thats how it was designed to be operated.

Depending on the car, starting off in 2nd or 3rd does nothing. In the majority of passenger cars and light trucks I've driven, the gear indicator is more of a "limiter" of sorts. In 1st, the trans will stay in 1st, not shifting to 2nd or higher, in 2nd, the trans will pick between 1st and 2nd, but no higher etc etc. The two Ford light pickups I've driven started in 2nd gear under normal operating conditions. On flat ground, the truck would start in 2nd gear unless you put the pedal down far enough to engage the trans. kick down, or you put the gear selector to 1st. I did get to drive a BMW Z4 and some full-size Hyundai that did put the transmission in the exact gear you selected, within limits. Obviously it would not allow you to start from a stand still in 4th gear. But it would start in 2nd, generally allowing 1 gear +/- from what a normal auto trans would select. Transmissions with modified valve bodies will allow you to pick exactly the gear its in, which will allow you to burn out the trans relatively quickly if you start in too high of a gear. Many older domestic transmissions can be modified with kits from B&M and the like. Unless Illum is driving a sports car or something with a modified transmission, it isn't likely he'll damage anything by selecting D3 or D2 when starting. The car will likely just start in 1st or 2nd, depending on how it was programmed. Some Volvos have a Winter mode in which they'll start in 3rd for additional traction, but again, thats quite specialized. Towing in OD isn't recommended because the transmission will have a tendency to repeatedly lock and unlock the torque converter and hunt between gears (up and downshifting), which will rapidly wear or glaze the clutch packs. This is why many owners manuals will recommend downshifting or disabling OD (OD is just another gear) if you notice your car hunting between gears. Its possible that the engine may have enough torque to overcome the holding force of the clutch packs, causing them to glaze over, but a properly designed and programmed transmission should downshift if it notices a large amount of throttle being applied.

 

[Illum]

Unless Illum is driving a sports car or something with a modified transmission, it isn't likely he'll damage anything by selecting D3 or D2 when starting. The car will likely just start in 1st or 2nd, depending on how it was programmed....Towing in OD isn't recommended because the transmission will have a tendency to repeatedly lock and unlock the torque converter and hunt between gears (up and downshifting), which will rapidly wear or glaze the clutch packs.

Either dad'd 2000[?] Honda Accord or the household's [2008] Hondai Santa Fe
The last time I disabled OD was because of a mountain road somewhere between here and Raleigh SC, where the engine was going up and down with the rpm everytime when we decsend from an incline.

When I do need towing, its usually under 1000lbs, well under a fraction or more of the vehicles ratings, I have not noticed the up/down shifts you spoke above, then again the terrain here is FLAT...and I do mean FLAT. Perhaps an incline plane may result in the symptoms you've described, but I'll be sure to read over that side of the manual again. :tinfoil:

 

[lightplay22]

Speaking of redundant systems on a hybrid (prius) made me remember that this is why insurance cost more for them than for a car that is much more expensive.

Getting all the stuff to work properly after a wreck or flood must be a nightmare!

Or, lol, do the insurance companies already know it is liable to "run away"?

 

[buickid]

Either dad'd 2000[?] Honda Accord or the household's [2008] Hondai Santa Fe
The last time I disabled OD was because of a mountain road somewhere between here and Raleigh SC, where the engine was going up and down with the rpm everytime when we decsend from an incline.

When I do need towing, its usually under 1000lbs, well under a fraction or more of the vehicles ratings, I have not noticed the up/down shifts you spoke above, then again the terrain here is FLAT...and I do mean FLAT. Perhaps an incline plane may result in the symptoms you've described, but I'll be sure to read over that side of the manual again. :tinfoil:

Disabling OD would tell the transmission to go down a gear, resulting in increased engine braking, which is wise when descending a long incline.
The up/downshifts I speak of will only occur if the ECU and TCM (Engine Ctrl Unit and Transmission Control Module) determine that there isn't enough power in the current gear to sustain your desired speed. Whether that be because of an incline, or because your foot is going further toward the floor :devil:, the transmission will drop down a gear so its comfortable. When your reach your desired speed, the various computer think "oh, no need for the extra power anymore. time to upshift to save gas!" Of course if the incline is still there, your speed might decrease, at which point you'll put your foot again, starting the process all over. Some TCMs are smart and will notice this upshift-downshift-upshift pattern and hold the lower gear, but it you notice it hunting around, taking off OD or bringing it to the next lowest gear will do the trick. In the Honda, its probably something like D D3 D2 L. I just read a forum post that says the Honda manual states the car will start in 2nd if put into D2. That could be useful for additional traction in the snow, but a little worse if you put it there manually when accelerating from a stop. The torque converter will slip more since 2nd gear is a shorter gear than 1st, thus putting out more heat. Generally, automatics were designed to be left in D unless you A) need the engine braking going down hill, or B) notice it hunting around for gears.

 

[turbodog]

...the speed limiter in my truck is removed and it can likely reach speeds of 140 or whenever my firestone tires blow....

hahahahahahhahahahahahahahahhahahahahaha

fall down laughing....

 

[gadget_lover]

These are correct highway figures, the Prius gets 51 MPG city.

If you do the majority of your driving in city-cycle, you'll get the best MPG from a hybrid. If the majority is freeway, go diesel.

It's easy to confuse the EPA figures with reality.

I have two hybrids, a 2002 Prius and a 2010 Camry. The design really shines when driving on the freeway. Their performance in stop and go traffic is far better than any other type of car. A 500 mile trip down California's I-5 in the new Camry (including stop an go in LA for an hour) averaged 10% better than the EPA figures. A followup trip to Oregon (another 500 miles) also gave better highway mileage than the EPA figures.

The city driving, on the other hand, seldom reaches the EPA figures since I almost always take short trips when driving in town.

Daniel

 

[Patriot]

Illum, shifting into neutral at every light will wear out your linkages, but nothing to worry about, it is cheap to fix. However starting off in D2 or D3 is a TERRIBLE IDEA especially if you are carrying a heavy load. ONLY start of in D2 if you need extra traction on ice, snow, or wet road. In an automatic transmission there is a wet clutch pack for every gear, typically as you go higher in gear, the clutch packs get smaller and can't handle as much torque. In D3 the torque converter will multiply the torque fom the motor, so starting from a stop will most likely cause the clutch pack to slip and burn up. This is why it is bad to tow in OD. If you want your poor transmission to last BREAK YOUR HABBIT!

buickid
IMHO, shifting into the Neutral at every light is worse for the trans. When going back into gear from Neutral, the clutch packs re-engage the planetary gears, during which they are slipping for a short period of time. Same thing happens with each shift, but in this case the planetaries are at a stand still with no chance for RPM-matching, as would happen when the car is in motion. Probably not a whole lot of extra wear, but its better just to leave it in gear at a light, as thats how it was designed to be operated.

Big time....to what these guys stated. Continuously running a trans in and out of engagement is pounding the liv'in dog cookies out of it. Btw, linkages will be the least of your concerns with this habit. The internals are what really suffers. It's also hard on the drive shafts and diff and pinion seals. A constant load is good but alternating loads or reversed loads are bad. You're essentially doing a mini neutral drop every time you disengage and reengage.



Regarding the transmission starting point that buickid brought up. He's right that starting in a gear too high, under abnormal load, will cause undo wear. The K2 clutches wear prematurely. At very light load modern trannys often start in second for economy sake but with a little more load they quickly shift to first. Doing this manually leaves it up to the drivers to decide what "excessive load" is and so you could be wearing out the clutches without knowing it. In speaking of "loads" I'm not talking about weights or payloads, rather I'm referring to dynamic loads during acceleration. It's really much better to let the mechanicals operate the way the engineers designed them to operate.

 

[HarryN]

Frankly - I am kind of surprised that with a problem this large, they are allowed to keep selling these cars.

I know that if I had a product problem that big
- People dying
- The Feds kicking me around for safety risk and lying
- Massive potential liability if more people die, and I knowingly had kept selling a product with a known critical defect

There is no way that I would keep selling a product like that.

At a minimum - I would call in all of the potential cars with the problem and re-chip it to cut 50 hp off the top to reduce the potential for run away events.

 

[Mjolnir]

Lowering the car by 50 HP wouldn't do anything significant if this problem truly is happening. First of all, that would leave the prius with only 49 HP, which would be a little low...
I have a feeling that, if the runaway acceleration is true, then the issues are caused by people not knowing how to react to the situation. I'm not really sure why the brakes would actually stop working in this kind of situation. Likewise, you could just put the car into neutral.
If something really is happening to make the brakes ineffective, then subtracting some horsepower wouldn't do a whole lot (unless the car has 49.5 HP to start with...)

 

[HarryN]

Lowering the car by 50 HP wouldn't do anything significant if this problem truly is happening. First of all, that would leave the prius with only 49 HP, which would be a little low...
I have a feeling that, if the runaway acceleration is true, then the issues are caused by people not knowing how to react to the situation. I'm not really sure why the brakes would actually stop working in this kind of situation. Likewise, you could just put the car into neutral.
If something really is happening to make the brakes ineffective, then subtracting some horsepower wouldn't do a whole lot (unless the car has 49.5 HP to start with...)

You are probably right - my brush was too broad on the HP drop. The thing that concerns me is that very experienced drivers are having the problem, and you would think that putting the car into neutral or shutting down the engine but allowing steering would be something they would know.