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+--- Thread: Public Service Announcement: I saw many Toyotas (/showthread.php?tid=93732)
Re: Public Service Announcement: I saw many Toyotas - Racer X - 03-04-2010
N-OS X-tasy! wrote:
[quote=mikebw]
There is a difference between the engine overcoming the brakes, and the brakes overcoming the engine. If the car is already stopped there is no momentum on the rotors, fully apply the brakes and you get a great amount of static friction, then go to WOT and the brakes will probably hold. Now if you start with the car in motion at WOT, when you apply the brakes there is a large amount of kinetic energy to convert to heat in order to stop the car, and the hotter the pads get the less effective they will become. So I think it would very much depend on the situation whether or not the brakes will win.
Precisely.
Exactly. A 3500 pound car, and hundreds of lb/feet of torque rotating the drive train, traveling at 100 mph, brakes aren't gonna overcome that unless the engine loses power. UNLESS you take it out of gear.
For every vehicle going back decades, there are SAE specs for brake specific horsepower of an engine, and the amount of torque and kinetic energy the brakes can overcome. When the BSHP is greater than the brake stopping force, you are screwed. But since when you use the brakes, you are supposed to stop accelerating (under non racing conditions) this problem isn't supposed to be an issue.
My 99 Sable went to WOT about 6 months ago. I popped it into neutral, stopped pretty quickly, and shut the ignition off. No big deal. Hasn't happened since. My ex-wife's '90 Tempo did it twice. Once to me, once to her. Don't panic and deal with it.
Re: Public Service Announcement: I saw many Toyotas - N-OS X-tasy! - 03-04-2010
Wot the hell does WOT refer to?
Re: Public Service Announcement: I saw many Toyotas - N-OS X-tasy! - 03-04-2010
Dakota wrote:
Before she died, the 5-foot-2, 125-pound woman told relatives she was practically standing with both feet on the brake pedal but could not stop the car from slamming into a building. Records confirm that emergency personnel found Grossman with both feet on the brake pedal.
Before she died? So while she was fighting a runaway car she called someone and explained all that and still managed to keep her feet on the brake pedals after she died.
Haven't read the article, but quite possibly she was alive long enough after the crash to speak with relatives. Not everyone who has been involved in these crashed died immediately.
Re: Public Service Announcement: I saw many Toyotas - Buck - 03-04-2010
N-OS X-tasy! wrote:
Wot the hell does WOT refer to?
I think they mean wide open throttle.
Re: Public Service Announcement: I saw many Toyotas - pRICE cUBE - 03-05-2010
Buck wrote:
[quote=N-OS X-tasy!]
Wot the hell does WOT refer to?
I think they mean wide open throttle.
A sphincter says WOT?
Re: Public Service Announcement: I saw many Toyotas - JoeH - 03-05-2010
Racer X wrote:
[quote=N-OS X-tasy!]
[quote=mikebw]
There is a difference between the engine overcoming the brakes, and the brakes overcoming the engine. If the car is already stopped there is no momentum on the rotors, fully apply the brakes and you get a great amount of static friction, then go to WOT and the brakes will probably hold. Now if you start with the car in motion at WOT, when you apply the brakes there is a large amount of kinetic energy to convert to heat in order to stop the car, and the hotter the pads get the less effective they will become. So I think it would very much depend on the situation whether or not the brakes will win.
Precisely.
Exactly. A 3500 pound car, and hundreds of lb/feet of torque rotating the drive train, traveling at 100 mph, brakes aren't gonna overcome that unless the engine loses power. UNLESS you take it out of gear.
For every vehicle going back decades, there are SAE specs for brake specific horsepower of an engine, and the amount of torque and kinetic energy the brakes can overcome. When the BSHP is greater than the brake stopping force, you are screwed. But since when you use the brakes, you are supposed to stop accelerating (under non racing conditions) this problem isn't supposed to be an issue.
My 99 Sable went to WOT about 6 months ago. I popped it into neutral, stopped pretty quickly, and shut the ignition off. No big deal. Hasn't happened since. My ex-wife's '90 Tempo did it twice. Once to me, once to her. Don't panic and deal with it.
On top of that, there has been an identified issue with a number of Toyota models where the power brake booster does not develop full braking power when the engine is at wide open throttle. Toyota engines are not the only ones with that as an issue as well, it happens in other car makers models too. The most well known of these accidents, the Lexus crash with the phone calling passenger, they found evidence of high heating of the brake rotors, so the driver had tried the brakes.
As for popping into neutral, or shutting off the ignition, that requires familiarity with the proper method on each different "drive-by-wire" system in different makers cars. It is not the same as with a mechanical linkage where movement of the shifter or the key will definitely change the gear or shut off the engine barring a broken unit.. You have to provide the input the control box will recognize as "yes, I really really mean to do that", and that varies from car to car. In the case of the Lexus, holding in the Start button for several seconds was required to stop the engine; I don't recall what was required to get the transmission to shift out of gear at speed.
Re: Public Service Announcement: I saw many Toyotas - Racer X - 03-05-2010
"On top of that, there has been an identified issue with a number of Toyota models where the power brake booster does not develop full braking power when the engine is at wide open throttle. Toyota engines are not the only ones with that as an issue as well, it happens in other car makers models too:
YES! WOT usually has the LEAST intake vacuum signal, and vacuum is what most power brake boosters work off of. Many diesels have electric vacuum pumps, and Buick (among others) used power steering pump pressure for brake assist.