WOT Braking

[Volvo_ST1]

Originally Posted By: Nick R
Originally Posted By: Volvo_ST1
Originally Posted By: Nick R
So, I did an experiment, with a few cars. I would be driving down an empty street, floor it, and press the brake down as hard as I could.


Why?


I've explained why. Apparently it's not important to know if your engine cuts out if you slam on the brakes, for whatever reason.


I'm not afraid of the "throttle getting stuck" (better known as confusing gas and brake).

An engine is not supposed to "cut out," no matter how hard you brake. Should the throttle get stuck, which is an extremely unlikely event, you turn the engine off.

I guess you would like to see a system that recognizes conflicting input, gas and brake, and defaults to "brake priority" by engaging fuel cut-off.

 

[Landrew]

I found it.

You can actually put the car in N or neutral to the lay person - essentially cutting engine power to the transmission - amazing whodof thunk it!

I've had a stuck throttle on a custom Turbo'd car. I simply put the clutch in and turned the ignition one click back so I killed the engine but not locked the steering. It was second nature.
I once drove a car home about 25k in the city with a broken clutch cable - rev matching does wonders.

I think with driving tests should really come a few questions on how a car works!

For those that can't figure out how to do that then I suppose we can expect them to use the brakey things pedal.

More braking vs. engine tests linked below.

Even a Roush Stage 32 Mustang had brakes stronger than the engine:

http://www.caranddriver.com/features/09q4/how_to_deal_with_unintended_acceleration-tech_dept

 

[Volvo_ST1]

Originally Posted By: Landrew
You can actually put the car in N or neutral to the lay person - essentially cutting engine power to the transmission


You see, Nick wasn't talking about cutting power to the wheels, he was talking about the engine automatically "cutting out." I asked "Why?" because I found his expectation to be unreasonable.

 

[Landrew]

I thought just in case some checking this thread may not know that. It sounds a bit far fetched to not know the Neutral solution but they are out there. I think everyone needs a refresher course in the basics. I know I myself have sometimes tried to find the difficult solution when an easier one is present (and often pointed out by my kids, wife, friends and co-workers, and usually not the Police) - ha

 

[wallyuwl]

Why does the engine have to cut out to conclude a car is safe in this regard? It would also be effective for the engine to keep running, but there to be a fuel cut-off.

 

[SteveSRT8]

you're going to have to explain how you can cut the fuel off and yet keep the engine running!

 

[javacontour]

Originally Posted By: Nick R
I knew full well that the cavalier wouldn't cut out, but it was interesting that it couldn't outbrake the engine. My own cavalier wouldn't brake to a stop at WOT either. I was just surprised that these supposedly "modern" DBW cars didn't cut out.


Don't think of it as not being able to out brake the engine. Think of it as an engine so powerful, mere brakes cannot hold it back.

I wonder what results you would get in higher gears.

 

[suspiciousmind]

I predict a new rash of "stuck throttle crashes" involving vehicles from multiple auto manufacturers.....starting today.

 

[2Fast4U]

This thread doesn't make sense at all. In a braking 'event' the engine should NEVER cut out.
Probably only a few things should ever cause an engine to 'cut out'. Some type of impact or roll over or fuel shut off. What kind of braking power is a vehicle going to have once vacuum is gone?

 

[bigmike]

In my old '94 Accord w/o ABS and with A/T, I had to hit the brakes in a major panic stop once. The engine kept running, but the A/T went into neutral.

Everytime I bleed my brakes, I do the poor man's ABS job by going down a back street and hitting my brakes hard enough to activate the ABS. Last time I did it in my Silverado I thought I had [censored] myself a bit, but no other problems and they worked fine, along with no engine shutdown to report. I've yet to do this in the 09 Accord.

I'm curious as to if all the oil is being forced to the front of the engine block (or side, if side mounted FWD) during this kind of braking procedure?

 

[brandini]

I think the VW, depending on year, just reduces power since the enthusiast market may actually want to left foot brake during an autocross. It was tested on video but I can't recall where.

 

[NateDN10]

Originally Posted By: 2Fast4U
This thread doesn't make sense at all. In a braking 'event' the engine should NEVER cut out.
Probably only a few things should ever cause an engine to 'cut out'. Some type of impact or roll over or fuel shut off. What kind of braking power is a vehicle going to have once vacuum is gone?

IIRC, one of Toyota's fixes for their unintended acceleration debacle was to cut engine power if the brake and throttle were on simultaneously.

 

[2Fast4U]

Originally Posted By: NateDN10

IIRC, one of Toyota's fixes for their unintended acceleration debacle was to cut engine power if the brake and throttle were on simultaneously.


This will more then likely cause more accidents. What do they currently use for brake vacuum? Probably start having people hard/emergency brake on the freeway and then their car stalls out and they get hit by the people behind them. What happens when cruise control is engaged and someone slams on the brake?

 

[stephen9666]

Originally Posted By: 2Fast4U
This thread doesn't make sense at all. In a braking 'event' the engine should NEVER cut out.
Probably only a few things should ever cause an engine to 'cut out'. Some type of impact or roll over or fuel shut off. What kind of braking power is a vehicle going to have once vacuum is gone?


I think you might be confused. When these cars "cut out," they don't shut off the engine. I think they just reduce engine RPM.

Also, I believe an engine at low RPM produces more vacuum than an engine at high RPM, so there wouldn't be a problem with vacuum.

 

[Quattro Pete]

Originally Posted By: 2Fast4U
This thread doesn't make sense at all. In a braking 'event' the engine should NEVER cut out.

What he's doing has absolutely nothing to do with a braking event. He floors his gas pedal and holds it there while applying the brakes. Who brakes this way in a car with auto tranny?

 

[NateDN10]

Originally Posted By: stephen9666
I think you might be confused. When these cars "cut out," they don't shut off the engine. I think they just reduce engine RPM.

Also, I believe an engine at low RPM produces more vacuum than an engine at high RPM, so there wouldn't be a problem with vacuum.

+1

They theorized that one of issues with the Toyota acceleration was people repeatedly stomping brakes while the engine was at WOT. Since the throttle is wide open, there's practically no vacuum, so after a couple stomps your brakes aren't very effective.

 

[FZ1]

Originally Posted By: Nick R
So, I did an experiment, with a few cars. I would be driving down an empty street, floor it, and press the brake down as hard as I could. Borrowed cars from friends for the experiment, as they were curious to see what would happen. This is what happened.

My Focus: Stopped, but the engine did not cut out, the brakes (barely) overcame the engine power in first gear.

2008 Corolla: Borrowed from a friend to test. Same thing, did not cut out under WOT and heavy braking, took much longer to stop than the focus did

2009 Civic: Engine cut out Under WOT and braking

2007 VW Jetta: Engine did not cut out, but it stopped much faster than the others did.

For [censored] and giggles, 2001 Cavalier: Did not stop. Did not cut out, and brakes couldn't overcome engine power in first gear.

2007 Mustang V6 (ours): Engine cut out under WOT and braking.



This was very interesting to me. Only the honda, and our mustang actually cut the throttle off when I hit the brakes. All the others kept pulling.

I predict a [censored] storm.
Come on,man!

 

[Rix]

Yeah they just return to idle basically.
they don't shut the engine off, they don't stay at WOT anymore.

When the cruise is on, it gets cancelled as soon as you hit the brakes.

 

[01rangerxl]

The lesson from this is that throttle cables are the way to go.

No worries about my truck barreling down the highway out of control, and if I want to do a brake stand it happily obliges.

 

[2Fast4U]

Originally Posted By: stephen9666

I think you might be confused. When these cars "cut out," they don't shut off the engine. I think they just reduce engine RPM.

Also, I believe an engine at low RPM produces more vacuum than an engine at high RPM, so there wouldn't be a problem with vacuum.



OP states "but the engine did not cut out" and "2007 Mustang V6 (ours): Engine cut out under WOT". I've been around/ working on cars for years. When someone tells you to "cut the engine".... they don't mean let off the throttle. We are to believe a 2007 Mustang at WOT then full brake goes to idle and does not stall or cut out?