What benefit or purpose is there to having a car creep forward when there's
no go-pedal input? Plus,if your foot is on the brake,such a "feature" still
consumes battery power despite the car being stopped.
It's still an automatic,as the tranny is controled by electonics and not by
a mechanical shift lever and clutch.Its internal construction more closely
resembles an auto tranny than a manual.
In a car where the driver doesn't have to constantly use a big stick to
manually stir a box full of gears, drivers of such vehicles are used to a
particular type of behavior from the vehicle.
Toyota evidently attempted to avoid frightening the herd with strange and
unfamiliar things, such as presenting them with an "automatic" that does
not creep forward when the brake pedal is released. And so the Prius mimics
the traditional "automatic" that everybody knows so well, even though it
doesn't actually _need_ to behave that way.
As for power consumption, I'm guessing that there is _no_ drain through the
electric motor when the brake pedal is depressed hard enough to hold the
car still. The PCM, which is already consuming power by virtue of being in
its "RUN" state, will monitor the brake pedal position, and will only feed
power to the electric motor if your foot lets the brake pedal up to the
point where the PCM decides that it should start making the car move. I
can't see that monitoring should consume any more power than the PCM would
consume in any case while in the "RUN" postion.
Because it's an automatic transmission (no manual shift required) car,
and every automatic trans car that's been sold since day 1 has (by
necessity) the creep feature.
Toyota worked very hard to hide the magic and make this behave, for all
intents and purposes, just like the automatic Corolla that the buyer
just traded in.
just because gas engines were stuck with that inherent trait means you copy
I note that that "automatic creep" got many people in trouble via
"unintended accelleration",because they didn't keep their foot on the brake
when they placed the trtanny into "drive",and it lurched forward,THEN they
jammed on the gas instead of the brake. that "lurch" was the initiator.
Worse,in an electric car,that creep means you are using battery power even
though you aren't applying the GO-pedal;a waste of scarce battery power.
On the other hand, think of stopped traffic on a slight incline. Cars
that do not have that creep often slide back a foot or two as the driver
moves his foot from the brake to the gas pedal before starting from stop
because most drivers are too clueless to use handbrake when starting on
an uphill. That causes cars to bump into tailgaters behind them. The
creep feature acts as a manual brake in such cases, preventing such
Just don't confuse the two systems like many seem to do. Your dad's Five
Hundred and my friend's Freestyle have a cone and belt CVT which varies the
effective size of the driving and driven pulleys to change ratios, it still
requires a torque converter, reverse gear of some sort, and a high pressure
hydraulic pump to apply tension to the stainless steel belt.
The PSD in a Toyota hybrid mimics a CVT by varying the speed difference
between the 2 motor/generators to change ratios. It has no torque converter
or reverse gear and just has a small fluid pump to keep the bearings lubed.
Just to be clear, the Toyota system is still a CVT, but of a completely
A Ford transmission with a belt? That sounds funny. A belt carrying the
load in a big car's transmission? It's a steel belt, though. And heavy
duty. I have seen the working model at NY Auto Show.
Never having driven a Prius, I'm dependent on others' descriptions of its
I gather the Prius is set up so that it mimics a conventional car's
automatic transmission "creep" when at a standstill and in Drive. The
"creep" would be provided by activating the electric propulsion motor when
the brakes are released, the amount of activation being in inverse
proportion to foot pressure on the brake pedal.
My question is:Why have that creep?
It means the motor consumes power even while you have the brake on.
What purpose does it have?
Gas motors HAVE to idle and it's a characteristic of auto trannies to
transfer torque even at idle;thus the creep.
Theoretically,there should be no movement without pedal input in an
No, it doesn't.
There's no "push" against the brakes while the brakes are on, as with a
fluid-drive automatic transmission. The electric motors are not being
energized until the brake pedal is let up, then they're energized and
the car creeps.
Frankly, this is MUCH better than not having it creep at all. Imagine
grandma letting up on the brake pedal to ease the car out of the garage,
but instead of a tiny bit of creep she has to put her foot onto the go
pedal to make the car go. WHAM! she gives it too much go pedal, and
she slams the back corner of the car into the garage door frame.
Yeah, that creep is a GOOD thing.
Yes,it HAS to use battery power to "creep";
the electric motor doesn't produce force without it.
and I'm told the engine is not even on until battery power drops to some
point and/or over a certain speed.
How do you know this? Is this mentioned somewhere in the manual?
Got a CITE for it?
Because,frankly,if releasing the brake applies power to the motor,then
there would be a surge to overcome inertia just like if "grandma" applied
It may be slight,but still some lurch as the motor spins up.
Grandma (and Grandpa) evidently STILL does that....
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