[Whiplash7]

Originally Posted by bravo6

This would certainly help when panic braking and your foot presses both accelerator and brake pedals.

On the track, you could simply disconnect the brake switch and enjoy left foot braking.

Regarding throttle stuck open, one can pop the transmission into neutral, coast to the road side and turn off the engine, right? Would work for an automatic too.

The brake switches are normally closed, which means when the brake pedal is not pressed the switches are closed and 12v is passed through to the ecu. Hence if the brake switch is disconnected, most ECUs would recognize this as a failure in the switches and switch to some kind of limp our limitation mode.

[bravo6]

Oh is it? In that case, removing the leads going into the brake switch and connecting them directly would accomplish a bypass. (for track use where brake lights are not required)

[Whiplash7]

Originally Posted by bravo6

Oh is it? In that case, removing the leads going into the brake switch and connecting them directly would accomplish a bypass. (for track use where brake lights are not required)

Yes, in principle shorting the pins with a small load in the connector would do the trick. A load is required because ECUs are designed to recognise short circuit to battery and ground too.

[shazikon]

So no Heal-and-toe shifting in latest gen cars and wonder how do they manage to rev match when downshifting in a corner or an Lotus Elise or for that matter in a daily drive car on the road?

[Diesel_convert]

Originally Posted by shazikon

So no Heal-and-toe shifting in latest gen cars and wonder how do they manage to rev match when downshifting in a corner or an Lotus Elise or for that matter in a daily drive car on the road?

Heel and toe is possible because it detects clutch being pressed and allows the engine to rev!

[dj78]

Originally Posted by Rehaan

A 911 call made from the car:

"We're in a Lexus ... and we're going north on highway 125 and our accelerator is stuck ... there's no brakes ... hold on and pray ..." The call ends with the sound of it crashing, prosecutors said. (link)

.

This incident happened in San Diego California. I remember the coverage vividly as I used to live there at that time. This was the final trigger that prompted Toyota to issue the recall for probably the largest number of vehicles.

There have been multiple investigations by multiple agencies but I believe, till date, nothing has been concluded. There were majorly two theories:
1. Mechanical - Something interfering with the brake pedal such as a loose object or a dislodged floor mat. Recalled vehicles were fitted with a metal attachment on the brake pedal assembly.
2. Software glitches - This is where the investigation was inconclusive. The NTSB had even asked Toyota for the entire source code that goes in the ECU. Not sure if Toyota agreed.

[motorsan]

Originally Posted by Jeroen

As others pointed out, it seems odd that the brakes were not working. I would think that even with a stuck throttle stomping on the brakes would slow you down. I can't really think of any reason why the stuck throttle pedal would affect braking.

Jeroen

Found the following in the comments section of the link you quoted. This could be the reason.

Imagine that you are in a car that is speeding-up on its own. You may not notice at first, then you will press on the brake lightly, then some more. You still don’t realize that the car won’t stop accelerating, so you don’t panic stop right away, you just ride the brakes trying to maintain your speed. Now your brakes are heat-soaked, and the pedal is useless.

[Jeroen]

Originally Posted by motorsan

Found the following in the comments section of the link you quoted. This could be the reason.

Maybe, but on modern brakes it takes quite a lot of heat building up before they start fading, so Im doubtfull. Without data it is really difficult to form an opinion. What might be a factor is when people get into a situation with a stuck throttle they panick and might not be braking at all or simply not pushing hard enough. They might think they do, but that doesnt mean they do.

Most people dont deal well with life threatening situations at all. Few take appropiate actions. Slamming the brakes as an initial reaction is what most would do, but if that doesn't get the expected results, for many panick will set in. They do the wring things or fail to do anything.

Jeroen

[Rehaan]

I probably should have said this in my original post:

A nice feature that would keep everyone happy would be to have BTO automatically disable itself on sports cars, when they are put into "Sport" or "Race" mode. You could left-foot brake all you want then, and i think it would keep everyone happy.

Originally Posted by arjab

Source: The Car Connection

Nice links, thanks!

Originally Posted by josephnishanth

How then do we start and move a vehicle in a downward slope?

I'm not sure what the standard says, but each manufacturer might implement this in different ways. See what Toyota says :

Michels added that there are certain situations where drivers would want to intentionally use both pedals simultaneously, such as starting from a stop on a steep hill, or rocking the vehicle to get it unstuck from snow. For that reason, if the brake is depressed first (e.g., in order to hold the car on a hill), the engine will respond and the vehicle can be driven from a standstill, assuming the brake is then released. - source

Originally Posted by DerAlte

'Brakes also not working' is usually a (panic-driven) expression that actually conveys 'Braking is not effective'.

+ 100000!! Excellently put.

Originally Posted by jaideepshinh

Any car with a servo controlled throttle should have this as a fail safe (and in my opinion, would have this already present). I have a feeling this "technology" is already quite widespread.

Not all manufacturers who have DBW have actually applied this, but going forward it will be a requirement.

Yes, it is fairly widespread already. Quite a few luxury cars have had it implemented since as far back as 2002. See the 'source' link above for more details.

Originally Posted by RSR

However, I do not think this is something new that came about after the sad "unintended acceleration" episodes in the US.

I wasn't saying it was something new, or something due to the Toyota incidents. In fact, ever since the theoretical discussions of drive-by-wire, people have been freaking out about "what if...".

What i did say was that it will be in all cars in the next few years, and [implied that] perhaps the Toyota incidents have something to do with that.

Nice catch on the i20 review!

Originally Posted by bravo6

OT: Yup! Both servo and stepper motor can get the job done in a DBW system, but servos are costlier.

Which cars use steppers? How does a stepper know its position / prevent any kind of drift? Being an open-loop system I'd imagine this could be more dangerous?

Originally Posted by shazikon

So no Heal-and-toe shifting in latest gen cars and wonder how do they manage to rev match when downshifting in a corner or an Lotus Elise or for that matter in a daily drive car on the road?

Again, depends on implementation. Firstly, a lot of manufacturers have avoided implementing BTO on Manual Transmission cars.

Brake/Throttle Override is not applied to vehicles with manual transmissions because Honda believes that clutch is sufficient to allow the driver to decouple the engine power from the driven wheels. - source

Secondly, some manufacturers even build in a delay, and only apply BTO if the throttle pedal input is 'static' (unchanging):

[Honda] If that signal becomes static (meaning stuck) AND then the brake pedal is applied, after 0.1 seconds the throttle will be gradually reduced to near idle level over the course of about one-half second.

Lastly, I'm (pleasantly) surprised at how many BHPians try left-foot braking. However, i just want to point out to others reading this thread that its very DANGEROUS to try left-foot braking for the first time, as it can end up being a lot more forceful / confusing that you think. Please do NOT try this when there are other people or vehicles around.

cya
R

[amit_mechengg]

This feature is available in Fiat Punto and Fiat Linea too. Whenever accelerator and brake are simultaneously pressed at certain speed we get a Coherency error.
For the first time i was shocked to see the error, but upon investigation i found that its a security feature. Very sensible.

[Octane_Power]

Originally Posted by Rehaan

Lastly, I'm (pleasantly) surprised at how many BHPians try left-foot braking. However, i just want to point out to others reading this thread that its very DANGEROUS to try left-foot braking for the first time, as it can end up being a lot more forceful / confusing that you think.

^

OT - Since I was in school when I used to observe my dad drive and when I started driving, I was given this clear instruction from him: brake and accelerator both with the right foot, never use your left foot for it.

And I wonder how much time does left foot braking save afterall.. Not even a split second's difference in real-world driving conditions.

I trust my right foot's reflexes that it can switch between the A pedal and the B pedal quite swiftly without the need for the left foot to be kebab-mein-haddi!

-Bhargav

[amitoj]

Originally Posted by Rehaan

However, i think this would cover the quoted case, as there is a high chance that the throttle was stuck open for whatever reason.

R

I was actually hinting at the case where there is a bug in the ECU itself. Incidentally, Honda has issued a recall for Fit and Vezel that it sold in Japan to

rewrite the computer program to fix the engine-control defect

in order to fix unintended acceleration.

Honda Recalls 175,000 Fit, Vezel Hybrids for Control Flaw

[bravo6]

Originally Posted by Rehaan

Which cars use steppers? How does a stepper know its position / prevent any kind of drift? Being an open-loop system I'd imagine this could be more dangerous?

Even if servos are used, the ECU would still depend on the Throttle Position Sensor to make sure the throttle angle corresponds with the accelerator pedal position.

Also, depending on the car, more than one set of the above sensors would be provided for redundancy. If there is a conflict between the readings of two TPS sensors or the two A pedal sensors, a malfunction light would glow, and the engine put into limp mode.

[DerAlte]

Originally Posted by jaideepshinh

... The similar "Phenomenon"- what exactly do you mean by Break- Throttle Override? ...

Stall Control. There is a big difference between Stall Control and "Runaway situation" Control. And the vehicle speeds at which either applies. The Stall Control works at low speeds (City speeds). BTO is expected to work at equivalent of highways speeds in higher gears.

Stall Control prevents the driver from presenting a higher synthetic load than the engine can handle at that moment, which - if not controlled - can result in a stall with a nasty thud - which will put unwelcome stress on engine components. This is much more than trying to regulate RPM around the Idling figure.

A "Runaway condition" can occur due to many reasons, least of which is the Driver Demand. BTO relates to *this*. Other than switching the car off (which can have it's own unknown repercussions, for example - shutting off EPS, reducing controllability) there is no measure provided in a car which is the equivalent of what old buses and trucks diesel engines (governor-controlled mechanical injection) used to provide: a steel flex cable which would bring the control shaft to 0 position cutting off diesel injection - a direct mechanical override. THAT was "Runaway condition" Control - to come out of sticky situations when the controller rod would get stuck at a high RPM position. It was also a convenient way to switch the engine off.

In petrol injection, the same can happen if the throttle valve is stuck in a position greater than the current driver demand - produce a "Runaway condition" which the ECU doesn't have a control on normally, nor a means of directly knowing it is happening. ECU normally regulates the throttle valve actuator based on lambda measurement and driver demand, but the runaway condition is in defiance of that. The easiest is to set Driver Demand to 0 (throttle override), which will force the regulation loop to a. ignore Acc pedal position, b. forcibly shut the throttle valve and c. cut off fuel injection. Effectively, it is inducing engine braking. Now, please once again try to relate to the first post: BTO would seamlessly bring back control in such situations, without unnecessary hullaballoo and annunciation.

Originally Posted by jaideepshinh

... Servomotors are the industrial standard for all CNC machines. ...

Really? Anyhow, the actuator technology has no bearing on BTO.

Originally Posted by jaideepshinh

... it is that its already in use by many manufacturers, for over 10 years at least. I find it weird that people are trying to reinvent it here. ...

As I said earlier - your assumption!

Originally Posted by jaideepshinh

... I find it quite stupid how you gun these down without ever having tried this. I'm sure your assumption is based on googling it, ...

LOL Less stupid than you commenting without knowing what goes into it, and why. Googling? Pot calling a kettle black, eh? Maybe that is the only knowledge source / method you know of? As the vernacular saying goes - a person who went blind in the rainy season, sees everything green! Or the other one that talks of everything looking like a nail if one has a hammer.

Originally Posted by jaideepshinh

... I understand that you're probably not too happy ... before replying to my post in haste.

My happiness has nothing to do with other people agreeing with me or expressing something on the contrary. If I am right, good. If the person is right, excellent - I learn! Having knowledge doesn't make me a greater person, as much as not having it doesn't make me a lesser person. A Forum is not the place to take or give personal affront, hope you understand that. OTOH, your reaction reminded me of the reaction of some recalcitrant children I have met, when told their toy is not good enough! Thank you for the momentary amusement by triggering those memories.

[hamsa]

Originally Posted by josephnishanth

How then do we start and move a vehicle in a downward slope?I prefer to double pedal brake and clutch and then Slowly accelerate to prevent backward
Slide.

'Break Throttle Override' as the name suggests doesn't apply to the 'clutch'. As long as you are right-footing between the brake and the throttle, you should be fine. As Rehaan has pointed out, they may not even introduce this feature on manuals.

Or you can use the handbrake. http://www.wikihow.com/Get-Started-o...ansmission-Car

On the other side, there is the 'hill-hold' assist feature in many cars in India. I'm sure the manufacturers would remember to add this on automatics that also come with BTO in the future.

cheers