Shifting to "B"

Use it just for extremely long downhill runs, basically to avoid overstressing the brakes in a situation where the battery becomes so fully charged that the car will stop regen braking, rely entirely on the friction brakes. Using B in this case delays this transition.

I'd agree, it's poorly explained. It also puts a lot of onus on the driver, to judge what constitutes an excessively long downhill run. Pretty much the only time I use it on our 2010 is coming down a local ski hill.

 

Have you read your owner's manual? Has the salesman gone over the operation of your new car with you?

Many, many threads here discussing B mode. Google priuschat.com B mode.

It's basically like using low gear for descending long, steep grades, so you don't have to constantly apply your brakes.

 

Shouldn't you be on skis or snowboard rather than in your Prius?

 

And leave all those Prius abandoned up there?

Ana
typical places to use B in CA, Donner summit to Rosedale is a 6000 foot decent, Grapevine just north of LA, El Cajon pass seemed long and steep when I walked it.

Use it anywhere you would use L in a normal car. Someone at Toyota was too honest to call it L as it doesn't change to a lower gear.

B under the D in the Drive gears? | PriusChat

 

That's interesting. My car doesn't apply the brakes at all. I use the "B" on a short steep hill, about 1/2 mile in length... I end up riding my brakes, almost all the way down.

Maybe I'm doing something wrong? Does the car have to be stopped before you shift into "B"? I made the change on the fly.

 

nope. i use b after breakfast and d after dinner. still looking for L.

 

No. B only adds engine braking, a steep enough hill will still need friction brakes, just like a manual. It is more a "every little bit helps" kinda thing. Are you hearing the engine race?

Also it will have less effective if you wait until you have already run out of room in the battery, it is more effective from the top of the incline.

 

Thanks. I will practice with it. I did hear the engine race one time. (My hybrid battery meter never seems to go down. It's always one bar from the top.)

 

I use it in heavy stop and go traffic. Of course you run the risk of getting rear-ended, since your brake lights aren't working when slowing down. That said, you run a higher risk of getting rear-ended because someone is texting on their cell phone, whether your brake lights are coming on or not. On my old Chevy Volt, I used low gear at all times, as do a lot of Volt drivers. I don't think that is recommended in the Prius, and probably not a great thing to do in the Volt either, since in my opinion it puts added stress on the drive train.

 

L in the Volt is a different beast from B in the Prius.

B in the Prius will increase ICE RPM to add engine braking, which does increase engine wear, and reduces efficiency. Therefore, it's best to only use it when you need that engine braking to prevent the friction brakes from overheating (descending steep mountains), and use the brake pedal in D for normal operation.

L in the Volt merely increases the amount of regenerative braking that occurs when you lift off the accelerator. The stress to the drivetrain is the same as slowing down in D by lightly pressing the brake pedal, so it's really a matter of driver preference which gear is selected.

 

Yes, using B in the Prius is more like using the low gear in a conventional transmission. True it's driver preference in the Volt, but from my own personal experience and the failure of a major drivetrain component in the Volt (and thank God it was under warranty) tells me it does put a strain on the drivetrain. I used "sport mode" and "low" at all times, and it was a lot of fun. Nice to do on a lease, but not for long term ownership.

 

And I doubt use of L caused that failure - correlation is not causation. Like I said, light brake application in D would put the same stresses on the drivetrain, in a Volt. The only way to avoid those stresses would be to shift to neutral for braking, or wait until the last second to brake (so you're using maximum friction brakes and it can't regen).

Sport mode could, however, potentially stress things more, by simply making it easier to demand more power from the drivetrain.