Runaway Prius - Why did the brakes not work?

ckissick · 03-09-2010, 08:09 AM

Today's story about the runaway Prius in SoCal has me confused. They say the driver applied the brakes as hard as he could, but it still sped up. In an older car, you can floor the gas and the brakes, and the car will stop fairly quickly.

What is it about these newer cars that this doesn't work? Is everything controlled by a computer? I like my old cars.

BGCarrera32 · 03-09-2010, 08:26 AM

Because he was standing on the gas...

island911 · 03-09-2010, 08:30 AM

"Is everything controlled by a computer?" Pretty much.

Consider that the Prius has regenerative braking . .. I expect that means that when the smugger ...er, driver first step on the brake pedal, the computer tells the regen braking to start, and then, as the car slows closer to a stop, the friction brakes take over.

rick-l · 03-09-2010, 08:31 AM

Quote:

Originally Posted by BGCarrera32

Because he was standing on the gas...

That would have been a valid assumption to make back in the day when the accelerator moved the throttle plate and the brake pedal pressurized the caliper piston. Nowadays there is about 8 levels of control between them.

msk1986911 · 03-09-2010, 08:35 AM

Is there a reason why the controls could not be built such that the application of brakes and gas are mutually exclusive, as in, tapping the brakes causes the throttle to close, or at least back off?

m21sniper · 03-09-2010, 08:37 AM

Quote:

Originally Posted by ckissick

What is it about these newer cars that this doesn't work? Is everything controlled by a computer? I like my old cars.

Yes.

Quote:

Originally Posted by ckissick

I like my old cars.

So do i.

m21sniper · 03-09-2010, 08:38 AM

Quote:

Originally Posted by msk1986911

Is there a reason why the controls could not be built such that the application of brakes and gas are mutually exclusive, as in, tapping the brakes causes the throttle to close, or at least back off?

Is there some reason they cannot use a throttle cable?

m21sniper · 03-09-2010, 08:39 AM

Quote:

Originally Posted by BGCarrera32

Because he was standing on the gas...

Most likely that was not the case.

Just another run away toyota. One of thousands reported to date.

red-beard · red-beard's Garage

Quote:

Originally Posted by ckissick

What is it about these newer cars that this doesn't work? Is everything controlled by a computer? I like my old cars.

It has standard hydraulic brakes, but the brake pedal is not connected to them!

The brake pedal is connected to a pressure sensor which determines how hard you are pushing. It then collects various other inputs, speed, wheel rotation, battery capacity, etc, and determines how much application of the regenerative braking to apply, before it starts operating the hydraulic and/or anti-lock brakes.

This is all controlled by the same computer.

I'm surprised they haven't gone to fly-by-wire on the steering too...

ckissick · 03-09-2010, 08:40 AM

Quote:

Originally Posted by BGCarrera32

Because he was standing on the gas...

But the point is, standing on the gas should not make much difference. Back when 60 Minutes almost put Audi out of business with a totally false report on unwanted acceleration, Audi responded with a video in which they stopped the car pretty quickly even with the gas pedal floored.

URY914 · 03-09-2010, 08:40 AM

They need to install a master kill switch.

m21sniper · 03-09-2010, 08:40 AM

New cars really are disasters waiting to happen in some ways.

Just imagine what would happen if there was a mass EMP event over/in a US city and all the highyways have drive by wire cars cruising along them at 50-60mph when the event occurs.

Ugly.

BGCarrera32 · 03-09-2010, 08:41 AM

Toyota has a problem, but I’m not sure it’s what everyone thinks. We have media hysteria, but I’m not convinced. When I drive around, what do I see? People doing anything but driving. There’s the kids, the cell-phone, the Big Mac and fries, the radio turned up to 11. Not to mention the massive influx of Third World type drivers. But, who cares? We all know it’s the car’s fault anyway. Besides, everyone understands that litigation along with Congressional hearings will solve all our problems.

BGCarrera32 · 03-09-2010, 08:43 AM

Quote:

Originally Posted by m21sniper

New cars really are disasters waiting to happen in some ways.

Just imagine what would happen if there was a mass EMP event over/in a US city and all the highyways have drive by wire cars cruising along them at 50-60mph when the event occurs.

Ugly.

They would all stall because the EMI would toast the ignition system.

red-beard · red-beard's Garage

This particular case was a mechanically stuck pedal.

I would need to look at the code to see what happens when you put your foot to the floor on the gas and hit the brakes at the same time. There is no mechanical connection between any of the pedal and any of the systems. This is INSANE!

TerryBPP · 03-09-2010, 08:46 AM

Can you not pop it into neutral and just let the engine over-rev? Not sure on the Prius but definitely on the gas Toyotas.

red-beard · red-beard's Garage

Quote:

Originally Posted by BGCarrera32

They would all stall because the EMI would toast the ignition system.

With a Prius, if you lose the computer, you lose everything, except the hand brake. And the sad thing is, unlike a standard car, you would not understand. In a regular car, if you lose the brakes, your foot will go to the floor. Not so with a Prius.

Nope, I will never get into one of these. I know Ford has licensed some technology from Toyota. So I need to look at Fords implementation before I get into one of those.

correction: If the computer thinks it is malfunctioning, it will drop 2 solenoids and give you unboosted braking from the master cylinder on the front brakes only.

vash · vash's Garage

as a a kid, i was told in case of a runaway..as a last resort, go with friction. start grinding against the concrete divide....sound scary.

would it work?

HarryD · 03-09-2010, 08:51 AM

Makes you wonder exactly what is going on:

How To Deal With Unintended Acceleration - Tech Dept. - Auto Reviews - Car and Driver

VINMAN · 03-09-2010, 08:51 AM

Quote:

Originally Posted by red-beard

.
I'm surprised they haven't gone to fly-by-wire on the steering too...

Dont give them any ideas........

Once again I ask the magical question.. NEUTRAL??????