Overusing 'B' mode on the transmission???
#11
07-09-2012, 09:34 PM
Re: Overusing 'B' mode on the transmission???
on page 163 of the User's Manual;
(c) Using engine braking
To use engine braking intentionally, shift the selector lever to the “B” position and take your foot off the accelerator pedal.
During high speed driving you may feel that engine braking is less effective than that of conventional vehicle.
Do not continue normal driving with the transmission in “B” for a long time. This may cause decreased fuel economy.
CAUTION
Never put your foot on the accelerator pedal while shifting.
CAUTION
Always keep your foot on the brake pedal while stopped with the hybrid system on. This prevents the vehicle from creeping.

CAUTION
Be careful when using engine braking on a slippery surface. Abrupt shifting could cause the vehicle to spin or skid.
(c) Using engine braking
To use engine braking intentionally, shift the selector lever to the “B” position and take your foot off the accelerator pedal.
During high speed driving you may feel that engine braking is less effective than that of conventional vehicle.
Do not continue normal driving with the transmission in “B” for a long time. This may cause decreased fuel economy.
CAUTION
Never put your foot on the accelerator pedal while shifting.
CAUTION
Always keep your foot on the brake pedal while stopped with the hybrid system on. This prevents the vehicle from creeping.

CAUTION
Be careful when using engine braking on a slippery surface. Abrupt shifting could cause the vehicle to spin or skid.
#12
07-10-2012, 06:21 AM
Re: Overusing 'B' mode on the transmission???
I believe that I was mistaken, it appears that "B" mode does recover some of the braking energy, just not as much as normal "D" mode braking:
From Wikipedia:
http://www.techno-fandom.org/~hobbit/cars/b-mode.html
Another link:
http://prius.ecrostech.com/QandA/BMode.htm
From Wikipedia:
- gradual braking: Regenerative brakes re-use the energy of braking, but cannot absorb energy as fast as conventional brakes. Gradual braking recovers energy for re-use, boosting mileage; hard braking wastes the energy as heat, just as for a conventional car. Use of the "B" (braking) selector on the transmission control is useful on long downhill runs to reduce heat and wear on the conventional brakes, but it does not recover additional energy.[11] Use of "B" constantly is discouraged by Toyota as it may promote excessive wear on certain gears.[12]
http://www.techno-fandom.org/~hobbit/cars/b-mode.html
Another link:
http://prius.ecrostech.com/QandA/BMode.htm
When not to use B Mode
There is no benefit to using B mode in a situation normally calling for the use of the brakes (except one, see Advanced uses of B Mode below). If anyone, even someone who should know what they're talking about, tells you that in B mode you recover more charge to the battery, they are wrong. You recover less for the simple reason that the purpose of B mode is to throw energy away by spinning the engine. The B does not stand for Battery, it stands for Brake. However, as far as I know you will not hurt the car by using B mode inappropriately. If you press the accelerator, there is no difference between B and D modes. So, if you don't care about recovering braking energy to the battery and you get a kick out of flipping the Mode Selector Level to slow down, by all means do so. Just don't be surprised if other Prius drivers roll their eyes at you.
There is no benefit to using B mode in a situation normally calling for the use of the brakes (except one, see Advanced uses of B Mode below). If anyone, even someone who should know what they're talking about, tells you that in B mode you recover more charge to the battery, they are wrong. You recover less for the simple reason that the purpose of B mode is to throw energy away by spinning the engine. The B does not stand for Battery, it stands for Brake. However, as far as I know you will not hurt the car by using B mode inappropriately. If you press the accelerator, there is no difference between B and D modes. So, if you don't care about recovering braking energy to the battery and you get a kick out of flipping the Mode Selector Level to slow down, by all means do so. Just don't be surprised if other Prius drivers roll their eyes at you.
#13
07-10-2012, 09:15 AM
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Re: Overusing 'B' mode on the transmission???
FEEL FREE TO USE B MODE AS MUCH AS YOU CAN. I have entire write up on it at toyotanation, feel free to it also.
benefits:
1. faster than regenerative braking traction battery recharge
Just plain BS. "B" mode uses engine compression braking, throttle plate FULLY CLOSED (***), engine compression braking. "B" mode operates to the detriment of FULL regenerative braking. Regenerative braking may be partially active depending on the conditions.
2. absolutely fantastic for downhill controlled slow downs
Yes, helps to prevent, delay, frictional braking overheating/fading. And providing, of course, you're on a highly traction roadbed.
3. excellent for engine braking taking sharp corners at high speeds
Dangerous, that. This is a FWD vehicle, applying front compression "braking" (+ regenerative) with NO ABS capability can be fraught with peril. That's why regenerative braking is significantly reduced, in favor of front and REAR ABS "controlled" frictional braking, the instant even slight loss of traction is detected at the front wheels during braking maneuvers. Or TC, Traction Control, during/for acceleration.
cons:
Front biased braking, engine compression and/or regenerative has NO ABS resource capability, therefore can be fraught with peril should you encounter a slippery spot during same.
Again, that's why the system reverts to front AND REAR frictional braking the INSTANT there is an indication of a low tractive condition.
not aware of any. Whoever tells you it's hurting anything, does not know what they talking about.
Just as the use of frictional braking will deter from the use of regenerative braking so must engine compression braking. So it would be unwise to make use of "B" mode, engine compression braking, except when conditions warrant same.
Keep in ind one basic principle"
THIS VEHICLE DOES NOT HAVE TRANSMISSION.
Weird, this statement. Toyota's HSD concept uses a PSD, Power Split Device, to simulate a CVT, Continuously Variable Transmission.
Oops, remembered one con:
IT'S NOT HYDRAULIC BRAKES!! SO, DON'T FORGET TO TOUCH THEM, WHEN YOU REALLY GETTING CLOSE TO OBSTACLE IN FRONT OF YOU!
benefits:
1. faster than regenerative braking traction battery recharge
Just plain BS. "B" mode uses engine compression braking, throttle plate FULLY CLOSED (***), engine compression braking. "B" mode operates to the detriment of FULL regenerative braking. Regenerative braking may be partially active depending on the conditions.
2. absolutely fantastic for downhill controlled slow downs
Yes, helps to prevent, delay, frictional braking overheating/fading. And providing, of course, you're on a highly traction roadbed.
3. excellent for engine braking taking sharp corners at high speeds
Dangerous, that. This is a FWD vehicle, applying front compression "braking" (+ regenerative) with NO ABS capability can be fraught with peril. That's why regenerative braking is significantly reduced, in favor of front and REAR ABS "controlled" frictional braking, the instant even slight loss of traction is detected at the front wheels during braking maneuvers. Or TC, Traction Control, during/for acceleration.
cons:
Front biased braking, engine compression and/or regenerative has NO ABS resource capability, therefore can be fraught with peril should you encounter a slippery spot during same.
Again, that's why the system reverts to front AND REAR frictional braking the INSTANT there is an indication of a low tractive condition.
not aware of any. Whoever tells you it's hurting anything, does not know what they talking about.
Just as the use of frictional braking will deter from the use of regenerative braking so must engine compression braking. So it would be unwise to make use of "B" mode, engine compression braking, except when conditions warrant same.
Keep in ind one basic principle"
THIS VEHICLE DOES NOT HAVE TRANSMISSION.
Weird, this statement. Toyota's HSD concept uses a PSD, Power Split Device, to simulate a CVT, Continuously Variable Transmission.
Oops, remembered one con:
IT'S NOT HYDRAULIC BRAKES!! SO, DON'T FORGET TO TOUCH THEM, WHEN YOU REALLY GETTING CLOSE TO OBSTACLE IN FRONT OF YOU!
Last edited by wwest; 07-10-2012 at 09:21 AM.
#14
07-10-2012, 09:34 AM
Re: Overusing 'B' mode on the transmission???
Ok I didnt mean to start a pissing match between you two kids. I pretty much got all the information I was looking for.
Thanks guys.
Thanks guys.
#16
07-10-2012, 07:03 PM
Re: Overusing 'B' mode on the transmission???
We use the B mode on mountain roads all the time for miles at a time on very steep grades here in Colorado. No problems at all. The key feature I like about the B mode is it works at ANY speed and it ALWAYS slows you down. In a manual transmission a gear will only work for certain speeds. The B mode will slow you down! Also, It continues to work even if the battery is at 100%. To correct the comment above, the B Mode charges 80 to 100%.
#17
07-11-2012, 07:44 AM
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Re: Overusing 'B' mode on the transmission???
Perhaps I misspoke....
During the use of "B" mode the regenerative syste will still (attempt to) charge the hybrid battery, just slower than during the use of "normal" braking technique.
During the use of "B" mode the regenerative syste will still (attempt to) charge the hybrid battery, just slower than during the use of "normal" braking technique.
#18
07-11-2012, 11:06 AM
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Re: Overusing 'B' mode on the transmission???
Hello, soon going to be my same age. Just wanted to say my new XLE TCH when coming down a mountain in the brake mode, seems to charge rather quickly from 80% to 100%. Could be that i'm closely watching the few steep 16% grades and some hairpin turns that makes the battery seem to charge faster.
#19
07-12-2012, 07:22 PM
Re: Overusing 'B' mode on the transmission???
For the record, B mode does work above 70mph, but deceleration is very minute. It starts showing itself well at 60 and below.
No, Toyota called it CVT simply to keep folks at peace with some name they are used to. It does not have transmission, it has Power Split Device.
Toyota Prius - Power Split Device (PSD)
The Toyota Prius is packed with some pretty high-tech stuff, but at the heart of the Hybrid Synergy Drive (HSD) is a simple little device called the Power Split Device, or PSD. The PSD is a planetary gear set that removes the need for a traditional stepped gearbox and transmission components, and also the familiar rev-lurch-rev-lurch of acceleration in an ordinary gas powered car. It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.
http://eahart.com/prius/psd/
No, Toyota called it CVT simply to keep folks at peace with some name they are used to. It does not have transmission, it has Power Split Device.
Toyota Prius - Power Split Device (PSD)
The Toyota Prius is packed with some pretty high-tech stuff, but at the heart of the Hybrid Synergy Drive (HSD) is a simple little device called the Power Split Device, or PSD. The PSD is a planetary gear set that removes the need for a traditional stepped gearbox and transmission components, and also the familiar rev-lurch-rev-lurch of acceleration in an ordinary gas powered car. It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.
http://eahart.com/prius/psd/
#20
07-12-2012, 07:27 PM
Re: Overusing 'B' mode on the transmission???
No, during B mode, traction battery is charged faster than during normal regenerative braking. It is a proven fact, argue all you want to. I have simple proof to it either - rolling down the hill, 9% grade, 1 mile long, with B mode engaged for the 60% of it, produces THREE little full car symbols in ONE full bar(60mpg for 1 minute), which is - 3 x 50Wts of energy recovered. You CAN NOT reproduce this during normal driving.
