Can a car with an automatic transmission decelerate quickly enough to stall the engine?

[Rubycon]

I can understand in a panic the driver would jam the brakes and not depress the clutch pedal.

What about automatic cars? Why do they stall when stopped suddenly especially in a crash? Does the shock prevent the transmission from downshifting and slipping correctly?

 

[jaha2000]

Typically
Airbag deployment cuts the ignition system..

 

[CurseTheSky]

Originally posted by: jaha2000
Typically
Airbag deployment cuts the ignition system..

Yep, fuel cut-off systems for crashes would be my guess.

 

[Greenman]

Originally posted by: CurseTheSky

Originally posted by: jaha2000
Typically
Airbag deployment cuts the ignition system..

Yep, fuel cut-off systems for crashes would be my guess.

That's the answer. The fuel pump gets shut down so it doesn't spray gas at 32psi onto an engine that might be on fire. Seems like a good idea.

 

[imported_Imp]

Originally posted by: jaha2000
Typically
Airbag deployment cuts the ignition system..

I honestly did not know that. Very interesting.

 

[DarkThinker]

But I believe in cars with no safety system (very old), an instantaneous drop from speed X to Zero ought to be too fast for the system to shift fast enough, no?

 

[Rubycon]

Originally posted by: DarkThinker
But I believe in cars with no safety system (very old), an instantaneous drop from speed X to Zero ought to be too fast for the system to shift fast enough, no?

This is what I'm talking about. Yes there are safety systems like a low oil pressure switch that opens the fuel pump relay so if the engine stalls the fuel pump is cut off, etc.

But the question at hand is if the sudden deceleration is affecting the auto tranny's ability to prevent the engine from stalling?

Excuse my ignorance of the matter as I don't drive.

 

[Soccerman06]

How the hell do you not drive?

 

[PM650]

Automatics in most cars have a lock-up converter, which essentially changes it from a fluid coupling to a mechanical coupling - there is no slippage when cruising (although I have no idea how fast this could disengage). Even without a lock-up converter, the rpm difference between converter in/out will not be high (10% per wiki) so I suspect the transmission stopping very quickly would also cause the engine to as well. As far as down-shifting, I would agree that it would take much too long for it to do so quickly enough.

 

[DVad3r]

Originally posted by: Soccerman06
How the hell do you not drive?

There's tons of chicks that don't drive. My mom for example.

 

[sdifox]

Originally posted by: Soccerman06
How the hell do you not drive?

She's chaffered around in a big ass boat, excuse me, ship.

 

[woodie1]

Originally posted by: DVad3r

Originally posted by: Soccerman06
How the hell do you not drive?

There's tons of chicks that don't drive. My mom for example.

There are some cities where one can get around using public transportation so no one really needs a car.

 

[Gillbot]

i say no, i've locked my brakes up at 60+ on multiple cars. This stops the wheels completely and haven't had a car stall yet.

 

[brblx]

even if you have the best brakes and tires out there, the only way the engine is going to die in an auto is if there is a problem with the lockup converter. when working properly, it will disengage as soon as you hit the brakes.

 

[boomerang]

The fuel cutoff used to be accomplished with a accelerometer. It would sense the sharp deceleration and cut off the fuel. Ford used this method and had the reset in the trunk.

I'm not sure how it's done these days. I'm not sure airbag deployment would necessarily be the right way to do it. I'm thinking of a crash where you are rear ended.

 

[StageLeft]

Originally posted by: woodie1

Originally posted by: DVad3r

Originally posted by: Soccerman06
How the hell do you not drive?

There's tons of chicks that don't drive. My mom for example.

There are some cities where one can get around using public transportation so no one really needs a car.

That's like saying most people don't ride a bike so for them there's no point in ever learning or most people don't fall into water so no need to learn how to swim. Although technically correct...

 

[Rubycon]

Yes all public transportation in the past. Never had a need for a personal car. Today is the same. Although I've driven power equipment like electric lift trucks, cranes, and transports and that is nifty.

 

[JulesMaximus]

The impact shuts off the fuel pump and kills the ignition.

 

[exdeath]

http://www.therangerstation.co...ary/InertiaSwitch.html

 

[DVad3r]

Originally posted by: woodie1

Originally posted by: DVad3r

Originally posted by: Soccerman06
How the hell do you not drive?

There's tons of chicks that don't drive. My mom for example.

There are some cities where one can get around using public transportation so no one really needs a car.

Yup, when you're in TO you don't need a car technically. Now we're in the suburbs and while you still technically don't need a car, a 2 hour bus one way isn't a great option. If not for hitching a ride with me in the morning she would be suffering pretty bad.

 

[SparkyJJO]

My old 93 taurus had a fuel pump shutoff switch on it, that in the event of an impact hard enough was supposed to get triggered. Never tested it though