B drive? How does it work?

Image you driving a manual tranny car. Now when you go downhill, you might downshift from 5th to 4th to slow the car down without having your brakes overheat... also known as engine braking (that is the purpose of the "B" mode).

In the Prius, the "B" mode does the same thing (sort of). If I am correct, the "B" mode would not recharge the battery though.

 

you b needing to read this

 

"B" will recharge the battery and slow the car down. Like putting an automatic in 2nd. Don't drive with it on all the time though according to the manual use it only down hills then switch back to "D". I only use it for steep grades as I like to have the car roll with minimum resistance.

 

Yes, it's like a jake brake: it tells the computer to use the engine as a big air compressor when necessary to assist braking action. On average it makes less use of regeneration (energy recovery into the battery) so it reduces fuel economy, and so, like a jake brake, it should only be used to avoid riding the brake when going down a long hill. If you want to play with it in other situations it won't damage anything (except probably your fuel economy).

Clarifications:
- "B" stands for "Brake", not "Battery". The car always uses the battery for energy recovery whenever it can. You do not have to shift to "B" to do ths, indeed you should not use "B" for normal driving because it will do less energy recovery (on average, under most ordinary conditions) than "D".
- Unlike downshifting in a conventional transmission "B" does not change the gear ratio between engine and wheels. You will not get more wheel torque in "B". Still, it has been suggested that "B" may be useful when driving very slowly on very slippery conditions, because it may help prevent the average driver from hitting the brake pedal too hard.

 

Autocrossing, it's a form of autoracing, but you run against a clock not other cars, at least not car to car. A course is set up in any big parking lot or other such big area with cones. From a dead stop you "race" thru the cones. Penalties happen when you hit a cone and are counted in seconds off your total time. Any car can run autocross, so there are lots of different classes. Most of the time only a helmet, setabelts and decent tires are needed to compete. There may be a short drivers meeting to let you know the rules as well as a rule book. Most meets are run by SCCA rules.

 

It's for simulated engine braking, similar to going into 2nd in an automatic like someone in a post above mine mentioned. I've only used it when coming down a long and/or steep grade/hill, to avoid keeping a foot on the brake for an extended period of time while trying to keep my speed in check. Good for very hilly and mountainy areas. Being a snowboarder, I spend a lot of wintertime in mountain areas and have found B mode to be helpful in mountain driving.

 

Thanks for the info on the B mode. Next time I drive up Mt Washington, NH I will use it on the way down the 7.6 mile road. That should keep the brakes from overheating. I have never used the B, but will now that I know the purpose.