Sebring---- SUDDEN ACCELERATION

a faster response for acceleration

 

Seems like a "over-engineering" job to me.

 

I have read the majority of the responses you received and tend to agree
that the simplest explanation is application of the wrong pedal. That said,
I had an experience that I do not believe anyone else has related and this
could also have been a cause for the accident so I'll describe what happened
to me here in a completely different vehicle.

I was accelerating down an on ramp to an expressway and merging with the
flow in a 1991 Mitsubishi 3000GT. I pushed the pedal to the floor and
quickly found myself at 65MPH and accelerating even though I had taken my
foot off the pedal. IN another couple seconds I was over 90MPH and still
climbing! I thought about my options: shut down the ignition, apply the
brakes, reduce gears, etc. but all had possible undesirable results. I
decided to reach down and check the accelerator and found that my carpet
floor mat had managed to get up under the accelerator so was holding it
down. I pulled it free and the vehicle came back under control.

It was a harrowing experience and the split instant when I realized that the
vehicle had a mind of its own is what I'm certain that your wife
experienced. As I indicated above, the most likely cause was driver error,
but a misplaced floormat is another possibility so thought I would share my
story here.

Bob

 

Yep- the throttle body location can be anywhere and you still use the
same accelerator pedal and the same throttle servo. No custom cable lengths.

And the sick and twisted irony is that "throttle by wire" engines are
NOTORIOUS for having a sluggish throttle response compared to direct
cables. The software always optimizes the throttle opening rate to
minimize fuel consumption and emissions, rather than letting you bang
the butterflies open instantly the way you can when your right foot is
firmly cabled to the throttle blades. That is the NUMBER ONE gripe I
hear from Ram truck owners who have compared the new 5.7 Hemi to the old
5.9 360. Yes, the Hemi has more horsepower and torque, but the old 5.9
slams you back harder and quicker when you first punch it because it
responds instantly. I've also observed the same thing when comparing an
older cable-throttle 3.5L v6 to the newest throttle-by-wire 3.5L v6.

 

I remember one of my high school teachers who had been a police officer
grabbing a couple of us and chewing us out in the parking lot one day.
He'd seen a friend of mine stuff his stack of books under the driver's
seat, and he said "what do you think would happen if a book slid forward
and got wedged under your brake pedal?" and then told a story of how a
flashlight had come loose and gotten under the brake pedal of a squad
car one time resulting in a nasty wreck. Ever since then (and that was
25 years ago), I've been REALLY careful about the kind of mats I use,
and careful to never stow *anything* under the driver's seat.

 

Same goes for the very badly named "package shelf" behind the rear seat.
I'm amazed at the bulky, heavy stuff people crap up the shelf with. Stop
short, and everything on the shelf flies forward like a missile.

 

Back in my days as a service writer I drove hundreds of customer's cars.
Usually about once a week, something weird would happen. The throttle
sticking open happened twice. The first time, I just cut the ignition,
no sweat. The second time I stopped it with the brakes. That was a
little unnerving, since you don't expect a car to start accelerating
again when you modulate brake pressure as normal, but it worked fine.
Both of these occasions were separate, in V8-powered cars. The brakes
are easily more powerful than the engine in all but the most poorly
maintained systems.

Under no circumstances would I divert my eyes from the road with
something like that going on.

--Geoff

 

Amen. This is my only carp about the new Hemi.

--Geoff

 

When the government did their investigation they found that most of the
people who had this problem were new to Audi ownership and have prviously
owned an American made car. They also found that the space between the
brake and the gas was smaller on Audi's than on your typical American car.

 

One of the first things you should always do is put your toe under the
gas pedal and try to lift it back up. If that doesn't work, hit the
brakes and wait for the car to stop.

 

Not sure how relevant that is. I thought a case or two was/were reported in
the UK.

DAS

 

Yes, that is true. Even cars with a mechanical POSSIBLY could do this
if they have cruise control as it can also control the throttle.
However, as has been pointed out already, it would take several
simultaneously component failures for this to happen. Not impossible,
but certainly highly improbable.

I don't know anything about the design of drive-by-wire systems, but
fly-by-wire airplanes have thus far proven as safe as their predecessors
with mechanical controls. As a former software engineer, however, I
admit to being more nervous on a fly-by-wire airplane than on a
conventionally controlled one.


Matt

 

Saves weight and can allow even more automatic control of the engine.


Matt

 

The fuel injection on current mechanically operated throttle bodies is
controlled by the computer. I don't see how controlling the butterfly
is inherently any slower than controlling the fuel. And you need both
fuel and air to get the engine to respond.


Matt

 

WRT spark plugs, you are actually claiming that if I install

Well, that throws away my theory that the AIS actuator had anything to
do with idle control...

Toyota MDT n MO

 

maxpower cut and pasted:

maxpower replied:

Well, that throws away my theory that the AIS actuator had anything to
do with idle control...

Toyota MDT in MO

 

Good point; I too have had the accelerator pedal become held down
after flooring it due to a displaced/crumpled floormat.
I bet many people have experienced this at one time or another.
It is noteworthy, however, that the cause of the problem in this case
is usually very obvious after it happened.

 

Not true at all. If you slam the throttle open, the computer HAS to
respond with fuel at the same rate or the engine will backfire and
stall. It cannot "slow down" fuel delivery if you force an increase in
air delivery without leaning out the engine to the point that it would
backfire, stall, or at least detonate badly. So as long as the foot
connects directly to the butterfly valve, the operator can demand
instant power and will get it.

With full-up TBW on the other hand, the computer has complete authority
to open the throttle no faster than the software design allows, and that
"allowance" can include all sorts of factors to mitigate emissions and
increase economy to bump the CAFE numbers up. Maybe your foot hits the
floor in 250 milliseconds, but the computer can insist that the throttle
not reach wide-open for 1.5 seconds if it wants to.

And thats exactly what people are saying about the 5.7 Hemi versus the
old 5.9.

 

Read again what I wrote. I didn't say that the current hemi
implementation wasn't slower on throttle response, I simply said this
doesn't have to be the case. That is, the design isn't INHERENTLY
slower. The designers may choose to be slower, but that isn't an issue
with the technology, that is an issue with the designers.


Matt

 

The way I read the comment was such that it implied that conventional
throttling COULD be made to respond slower also. It can't. What threw me
off was your statement "I don't see how controlling the
butterfly is inherently any slower than controlling the fuel" since the
driver *never* directly controls the fuel in anything except a diesel.
Even with a carburetor, the driver controls the *air* and the fuel is
added in response- same with EFI and a cable throttle. Only a (non
computerized) diesel gives the driver direct control over fuel flow. So
it seemed to me that you were saying that since the computer still
controls fuel in a cable-throttle system, it can can slow the engine
response independently of the driver's foot on the throttle.