Ok I read the manual but it's not very detailed regarding the "B" brake thing on the shifter. What is this for since I already have a brake pedal and E brake on the car? How is it used, and when and for what?

 

This setting is like low gear in a regular automatic transmission. It's useful for going down long hills without overheating your brakes.

Mike

 

I find B useful on long downhill runs where the car tends to want to accelerate. More specificaly it is a compression brake. It uses the gas engine (usually refered to as ICE, internal combustion engine) as a compresson brake. Think Jacob's brake from a large truck and you have the basic idea, but a lot more quiet, although at high speeds when you engage B you can definitly hear it.

B also works well in panic city stopping. It can really help out regular braking, in some instances. Since B mode is accessed by being in D and just flicking down on the selector it is really fast to engage.

To get back into D, just choose D with the selector. Don't hover on N for any length of time or else you will go to N.

 

I dont have to use this feature we drive on flat land. The manual states if you drive around all the time in "B" you may burn the engine up. The "B" stands for Engine Brake, you use it for driving down steep grades (moutain / hill) driving, kinda like a "Jake Brake" on a semi truck.

 

Could you please point me to the exact page where the manual states that you will burn the engine up.

I don't see that as a possibility without running the vehicel without coolant or oil. And considering that during B mode the ICE is turning water and oil pumps and is pumping only air through its system (no fuel or ignition), I'm totally disinclined to believe that B mode would endanger the vehicle's ICE in any way.

 

Well Thanks for the heads up on my type-o..

This is what I ment to say,

Driving in "B" mode.




A couple of people have asked if the transmission on the Prius should be kept in "B" mode while driving in snowy/slippery/icy conditions. The "B" mode is for engine assisted braking, similar to downshifting in a car with a standard transmission. Use of the "B" mode is gentler and less abrupt than use of the friction brakes. When the car is in "B" mode, the internal combustion engine is spinning, and the weight and friction of this spinning slows the car.

Typical use of the "B" mode includes slowing the Prius on a steep downslope, while approaching an off-ramp on the highway, or approaching a stop sign or red light. Heavy use of friction brakes in slippery conditions can be dangerous. The "B" mode provides for more controlled slowing.

When the Prius is coasting in "B" mode, the battery is usually being charged. It has been shown that this is an inefficient way to charge the battery compared to friction braking. Some people use "B" mode hoping to avoid wear on their brakes. Other people fear what they think is "wear" on the internal combustion engine, and prefer to use their brakes. There has been a big debate about this. Read more:


In brief: engine braking is great way to slow the speed of a car while coasting to a stop, or going downhill, especially in slippery conditions where friction brakes can case the car to skid.

You don't want to drive in "B" mode. It won't provide extra traction, but it will cause extra drag on the engine and its componants.

 

B mode wastes more energy, but it's good for extended hills. On a Prius II your friction brakes do not get used at all until you press fairly hard (75%+) on the pedal. All the braking up to that point is done by the large electric motor that is directly connected to the wheels. B mode uses the electric motor to provide some of the braking as well as letting the ICE spin to provide more braking, this is especially good if your battery gets full since otherwise you would be using friction brakes only, but essentially 'wastes' that kinetic energy that could otherwise have been captured.