What is the "B"?

This is a wonderful design of Toyota. During traffic jam, moving inch by inch, you can swift to this gear. Step the gas paddle, car moves forward and when you release the paddle, the engin will do the braking for you(without burning any gas!). No need to step on brake unless you need to stop the car at that spot. It's a very useful design. Don't know whether Toyota got patent on that.
Enjoy. :cheer2:

 

Use it for engine braking. Basically, if you are driving down a steep decline (like down a steep mountain road), you can put the car into "B" mode and it will give additional engine braking.

It works much like "2" in a 3 speed automatic transmission. It allows you to not use the brake pedal as much and reduces your coasting ability.

I have only used mine a few times, and each time it was descending the Santa Cruz mountains. You may never use it and it may never need to be used.

I wouldn't use it in normal driving regardless of conditions.

 

Congrats on your new car!! I also just traded in a gas guzzler (Subaru Outback 3.0) for my first Prius. At any rate, I was told that the "B" is for when you are going down long declines (like in the Rockies or going over the Grapevine in California). I really don't know too much more, but was told most people will never need it.

 

No, that is an "incorrect" use of "B". It wastes the energy you could otherwise recover using regenerative braking.
ahmeow needs to be "educated".

 

"B" is just a waste of your time in traffic. Most likely you will forget you have it in B and its use will decrease you gas mileage. It's for use in really long steep downhill roads that you don't have in NJ.

 

If your regenerative brakes fill up, then you must have friction brakes, B mode adds engine braking, so your friction brakes do not heat up too much.

Because a Prius has no lower gears, someone at Toyota was too honest to call it L, but you use it when you would use L.

Above about 20 MPH, it is considerably more wasteful than just using the brakes, so use it when you want to waste energy, long steep descents. It is possible there are no long steep descents in New Jersey, so you may never need it. http://en.wikipedia.org/wiki/High_Point_(New_Jersey)

 

Newark's maximum elevation is 273 feet. B isn't useful until steep mountain descents exceed about 500 feet, and isn't really necessary without considerably more descent.

 

Yes, but the effect is minimal to non-existent on steep grades. There just isn't enough compression to counter gravity on steep grades. I know that the Catalina highway to/from Mt. Lemmon in Tucson averages a 5% grade. No way does B even come close to slowing the car on descent. I charge off after a few miles and the rest of the 15 miles is friction. Oh, but the display does look really nice after the trip down.

 

I definitely felt B on the Tail of the Dragon, but I think it is quite a bit more than 5%

 

I remember my salesman told me the B stood for battery. Now there's a guy who needs to get a little more product knowledge.


iPad ?

 

hmm ... my experience is different.

I can think of one specific moutain I drove down frequently from Los Alamos that absent braking would quickly lead to dangerous speeds, but taking my foot off the fuel pedal in B mode not only prevented the car from gaining speed, the car would slow down.

To the OP in NJ: you will never have a good reason to use B in your state.
The advice to use it in stop and go driving might save the occasional trip of your foot from the fuel to the brake pedal, but the cost is lost regen. Keep a longer following distance instead, and coast more.

 

Cool elevation map. Looks like roughly 2000 feet over 11 miles.

The example I gave was perhaps a bit more extreme --- roughly 5000 feet over 20 miles.

 

Thanks, SageBrush. I think the difference is the definition of "steep". I have no problem getting the car to slow down on lesser grades and the point I was trying to make is that it doesn't add much to steep descents; especially not as a substitute for friction braking.

 

Is that a very slow section of road, with little air drag?

B does the job for me on 7% grades at highway speeds, though the engine is howling. At 5%, I need to press the gas pedal a bit to slightly reduce engine drag.

On steeper hills at slower speeds, e.g. 8% at under 20 mph coming down Pikes Peak, then B is insufficient. It may be equivalent to downshifting a 5 speed manual to somewhere between 4th and 3rd gear. On hills needing 2nd or even close to 3rd gear, B is inadequate, and a B2 would be helpful.

 

Hello David,
I know the B can be use as 'L'. However you will find it the best time to use is during traffic jam going inch by inch. Of course normal traffic will never use it, wasting alot of energy. Decending deep slope is also helped by it. But still need to use the brake. Use during traffic jam is the best.
Try, have you?
Regards.

 

If you want to use it as a driving style, this won't hurt anything except a slight hit to MPG. But for maximum MPG, this use cannot beat simply using the brake, and cannot match a traffic-coordinated pulse & glide.

 

I decided to attempt a gross calculation of the *minimum* braking B mode is exerting in the route I mentioned. I looked up Google maps and Google Earth for distance and altitude data for the road highlighted in yellow below



I've assumed 30 mph, and no change in speed
100 meter drop
0.8 mile route

Drop in potential energy in joules is m*g*h = 1400*9.8*100 = 1372000 joules, equal to 0.381 kwh = 381 wh = 22860 w*min

The route takes 1.6 minutes, so the power dissipation is 22860/1.6 = 14 kw. That is a *very* conservative calc; my WAG is actual drag for that speed is at least double that amount.