Corolla down-shifts when braking downhill
Dan
certain braking power, it shifts down the transmission. I was trying
to figure out if that's a feature of the transmission and how does it
know that the car is travelling downhill.
It's probably intended for adding engine braking but sometimes it's
just annoying since revs go up and it strains the engine and
transmission.
BTW, no down shifting when braking on a level road.
Bill
That could be done fairly easily with a tilt sensor as well as input from
the brake pedal and speed sensors. You might find information on this in
your owner's manual? Don't ask a salesman because they don't understand
technical things and you will likely get misinformation.
The best source of information would be a factory service manual set of
books (sometimes 4 books to the complete set) which you can order from a
dealer. These have "descriptions of operation" for each thing in the vehicle
and will many times be quite detailed.
As to sensors, the following link sells easy to program microcontrollers,
robots, and sensors of all types. Click on Sensors, then Tilt, then you can
read all about how these work...
http://www.parallax.com
jim beam
> 2006 Corolla, when it's downhill and I press the brake pedal above a
> certain braking power, it shifts down the transmission.
it's supposed to.
> I was trying
> to figure out if that's a feature of the transmission
yes it is. it helps reduce brake load, thus premature wear, and in
extreme cases, brake overheating.
> and how does it
> know that the car is travelling downhill.
brakes are on, throttle is closed and speed is maintained above a
certain level.
> It's probably intended for adding engine braking but sometimes it's
> just annoying since revs go up and it strains the engine and
> transmission.
rubbish. any load from engine braking is well within the capabilities
of both engine and transmission and lower than when the gas pedal is down.
> BTW, no down shifting when braking on a level road.
--
nomina rutrum rutrum
jim beam
> "Dan" wrote in message
>> 2006 Corolla, when it's downhill and I press the brake pedal above a
>> certain braking power, it shifts down the transmission. I was trying
>> to figure out if that's a feature of the transmission and how does it
>> know that the car is travelling downhill.
>> It's probably intended for adding engine braking but sometimes it's
>> just annoying since revs go up and it strains the engine and
>> transmission.
>> BTW, no down shifting when braking on a level road.
>>
>
> That could be done fairly easily with a tilt sensor as well as input from
> the brake pedal and speed sensors.
doesn't need tilt sensor - it has the engine rpm's and speed. otherwise
referred to as "grade logic". just map and program transmission shift
points accordingly.
> You might find information on this in
> your owner's manual? Don't ask a salesman because they don't understand
> technical things and you will likely get misinformation.
true dat.
>
> The best source of information would be a factory service manual set of
> books (sometimes 4 books to the complete set) which you can order from a
> dealer. These have "descriptions of operation" for each thing in the vehicle
> and will many times be quite detailed.
>
> As to sensors, the following link sells easy to program microcontrollers,
> robots, and sensors of all types. Click on Sensors, then Tilt, then you can
> read all about how these work...
> http://www.parallax.com
>
>
--
nomina rutrum rutrum
chuckcar
af7693...@r27g2000yqb.googlegroups.com:
Well if you slow down, the car will shift to a lower gear. You *do* realize
that don't you?
How many speeds in your automatic transmission? That certainly will have an
effect as well.
As for "straining" he transmission and engine, just how many RPM are you
getting up to when this happens?
--
(setq (chuck nil) car(chuck) )
Hachiroku ハチロク
> "Dan" wrote in message
>> 2006 Corolla, when it's downhill and I press the brake pedal above a
>> certain braking power, it shifts down the transmission. I was trying to
>> figure out if that's a feature of the transmission and how does it know
>> that the car is travelling downhill. It's probably intended for adding
>> engine braking but sometimes it's just annoying since revs go up and it
>> strains the engine and transmission.
>> BTW, no down shifting when braking on a level road.
>>
>>
> That could be done fairly easily with a tilt sensor as well as input from
> the brake pedal and speed sensors. You might find information on this in
> your owner's manual? Don't ask a salesman because they don't understand
> technical things and you will likely get misinformation.
And this is a shame. Toyota salesmaen (most of them) used to really know
the product and could answer the questions. Now, they're *just* salesman
and would be selling Fuller brushes if they weren't selling Toyotas...
Hachiroku ハチロク
It should be freewheeling. The only time it should downshift is when the
rpms and the speed gets below a certain level, and I'm not sure what that
would be for your car. It seems you should be going fairly slow before the
trans downshifts.
I would have the operation of the trans ECU checked.
Paul
I have never heard of any normal car doing that.
There are no level sensors that I have ever heard of.
Most cars down shift according to rpm and speed.
But it is at slow speeds. Like under 20 mph.
Is your trans fluid level normal?
Screen clean?
Bill
>
Vehicles are now more sophisticated than the first rockets to go into outer
space...
Bosch Automotive Sensors...
Drivetrain Safety Convenience features
Radar distance sensor
(Headlamp aiming system)
(Vehicle dynamics control)
(ACC, precrash)
Tilt sensor
Acceleration sensor (Airbag)
Tilt sensor (Vehicle security sensor)
Torque sensor (Power steering)
(Roll over sensing)
Angular rate sensor
Rotional speed sensor
Yaw rate sensor
Seat occupancy sensor (Airbag)
Manifold absolute pressure sensor
(Electronic diesel control, motronic)
Angular rate sensor (Navigation)
Air quality sensor (Air conditioning control)
Humidity / temperature sensor
(Heating and air conditioning control)
Pressure sensor
(Central locking system)
Rain sensor
(Wash/wipe control)
Pressure sensor (Electronic
transmission control, motronic)
Mass air flow sensor (Motronic)
Knock sensor (Motronic)
Atmospheric pressure sensor
(Motronic)
Oxygen sensor
Angular position sensor
(Motronic)
Tank pressure sensor
(On board diagnostics)
Rotational speed sensor (Electronic
transmission control, motronic)
High pressure sensor
(Vehicle dynamics control)
Steering wheel angle sensor
Acceleration sensor
High pressure sensor
(Fuel injection system, common rail)
(Antilock braking system)
(Antilock braking system)
(Vehicle dynamics control)
Ultrasonic distance sensor
(Rear proximity warning system)
Above from...
(See page 2 - take awhile to load after downloading)
http://robotics.eecs.berkeley.edu/~pister/etc/Bosch.pdf
jim beam
>> There are no level sensors that I have ever heard of.
>>
>
> Vehicles are now more sophisticated than the first rockets to go into outer
> space...
"electronic" != "sophisticated". there was a /lot/ of technology that
went into space. and a lot of it was bleeding edge. the stuff that
finds its way into consumer cars is /way/ down the food chain. it has
to be to be cheap.
>
> Bosch Automotive Sensors...
>
> Drivetrain Safety Convenience features
> Radar distance sensor
> (Headlamp aiming system)
> (Vehicle dynamics control)
> (ACC, precrash)
> Tilt sensor
that tilt sensor is for lateral stuff - like ditching.
> Acceleration sensor (Airbag)
> Tilt sensor (Vehicle security sensor)
and that one is as advertised.
not all of those are used on all vehicles. the high end, especially
4wd's use all the tilt/stability stuff to help with poor handling
dynamics fundamentals. "real" cars don't need it to anywhere near the
same extent.
--
nomina rutrum rutrum
Bob Cooper
af7693...@r27g2000yqb.googlegroups.com>, drn...@hotmail.com says...
It's called "grade logic control." Sometimes "grade logic system (GLS)"
Below is a Honda description. Looks like they tout it more than Toyota,
and have used it longer. Standard on autos since 1997.
Here's a Toyota reviewer reference to it for the 2005 Camry.
http://toyotabuyersguide.theautochannel.com/news/2005/03/24/020359.html
"Perhaps the most important upgrade is to four-cylinder models - a new
five-speed automatic transmission with electronic grade logic control
replaces the old four speed, for improvements in both performance and
economy."
Looks like your Corolla got a version the next year.
Personally, I like making the shift choice myself.
There's a big honking shift lever for that.
I would also find that Corolla shifting annoying.
My GM car freewheels down long, steep grades, exceeding the cruise speed
setting. A little braking takes care of that and the trans never
shifts.
Fine with me, since I'm hardly ever on those grades.
But a case can be made for its usefulness to downshift while in cruise
control.
Some who often drive grades often might like grade logic to keep cruise
control working.
You might make a case for using it on heavier vehicles which tow, as a
safety feature.
And when you think about it, a properly and quickly working system
should reduce braking distances in emergency stops done when in 2nd gear
or higher on any car.
But I like having the choice whether to use brakes or a lower gear to
maintain speed.
You should complain to Toyota.
At least they could put a disable function on the nanny shifting
for those who find it annoying or worse, or refine it somehow.
There are plenty of complaints about it, and some who like it.
Others start out not liking it, but quickly adjust to it.
Like all complexity added to control systems, errors occur.
Excessive engine braking while approaching a stoplight is one complaint
that is too common.
Here's a few Honda complaints, probably caused by bad programming or
sensors.
http://www.aboutautomobile.com/Complaint/2008/Honda/Civic/Automatic+Tran
smission
***********************************************************************
Grade Logic Control
To reduce gear "hunting" and unnecessary shifting, Grade Logic Control
and Shift Hold Control systems are integrated into the shift programming
of Accord automatic transmissions. Grade Logic Control alters the 5-
speed automatic's shift schedule, reducing shift frequency while
traveling uphill or downhill. Using inputs monitoring throttle position,
vehicle speed and acceleration/deceleration, Grade Logic compares the
operating parameters with a digital map stored in the transmission
computer. When the system determines the Accord is on a hill, the shift
schedule is adjusted to automatically hold the transmission in a lower
gear for better climbing power or increased downhill engine braking.
Clive
=?iso-2022-jp?q?Hachiroku_=1B$B%O%A%m%=2F=1B=28B?= <Tru...@e86.GTS>
writes
>It should be freewheeling. The only time it should downshift is when the
>rpms and the speed gets below a certain level, and I'm not sure what that
>would be for your car. It seems you should be going fairly slow before the
>trans downshifts.
>I would have the operation of the trans ECU checked.
unlawful in the UK. You'd certainly fail your driving test if you
selected neutral before coming to a stand and engaging the hand brake.
--
Clive
Hachiroku ハチロク
Not frewheeling that way, but the clutch packs allow the transmission to
spin more freely until certain revs are attained, and then the car
downshifts.
If you're doing 50MPH down a hill, the trans should stay in the highest
gear.