Ok, so I know that I could probably look this up in the discussions somewhere but I want to be lazy and just ask. Plus I figure I will get an answer more quickly this way than looking it up. So, the "B" option on the shifter of the Prius (Don't think it matters what year). I have read that it is for engine braking but there isn't that much in the manual about how to use it. I also do not want to be driving down the road at 55, put the shifter into "B" and find out what it does, especially if it results in calling for a tow truck. If anyone has used this and/or has a great application for using it, please shed some light on this mysterious option.

 

The Prius does not have 'gears' in the regular sense. All of the gears are always engaged and the 'shifting' happens by computer operation of the two motor generators, MG1 and MG2. What this means is you can shift from "D" to just about any other gear, except possibly "P", without risking mechanical damage. The car is very good about protecting the assets from 'operator error.'

You can go into "B" at any speed and it works. So don't worry about it, have fun.

The real use of "B" is to go down a long hill where you need engine braking to avoid having to use your mechanical brakes. It really needs to be a pretty steep hill too.

Bob Wilson

 

Thanks for the quick response. I understand that the Prius does not have gears/standard transmission. But I still don't feel comfortable moving the fake "shifter ***" (for lack of better terms) while the car is in motion. I have always owned a manual shift, so the idea of moving something in the car while it is moving makes me feel uncomfortable because I know that there will be a direct effect on the car. Downshift too far a couple of times and you will learn this very quickly. I take regular trips to the mountains of North Carolina so maybe I will give it a try next time I am out that way.

My other concern though is gas mileage. There must be a link between using the engine to brake and reducing your MPGs. Again, I travel to the mts of NC and this past weekend on my way back home I got to coast down a very large mountain and was able to achieve the Max (100 MPG) on the display (See Attachment). I guess the debate now comes, would it be better to use up your brake pads and get better gas mileage or save the brakes and reduce gas mileage.

Again, thanks for the help!

 

ATBound-NC — At speeds above ~40 mph, when fully warmed up, you have a choice between:
(a) Driving downhill in 'D' with very mild regenerative and engine braking, plus no gasoline usage at all (in fuel-cut mode; the FE gauge reads maximum mpg), supplemented by use of your friction brakes (which waste energy) if needed;
(b) Driving downhill in 'B' with much greater regenerative and engine braking, plus no gasoline usage at all (in fuel-cut mode; the FE gauge reads maximum mpg) — friction brakes aren't needed.
In both cases energy is being wasted in engine braking (and/or friction braking). In both cases no fuel is being used. It's your choice!

Stan

 

It is just a lower gear, nothing more. Common sense should take over after understanding this. I am amazed at how many threads are started about this where it is over analyzed to death. Maybe Toyota should have labeled it 1 for first gear instead of B.

 

SPL (Stan) -- Thank you for the explanation, If only they included that in the manual then all would be well with the world.

Resist -- Your explanation is horrible. If you tell someone who has never driven the Prius before that the B is just "First gear", then you have lied to them twice. Once because the Prius does not have "gears", and second because from the explanations that I have heard the use of "B" is for going downhill and not using the mechanical brake. First gear on any car is too low to drive with at any distance or at any speed beyond getting the car started. Having the option to shift in an automatic allows you to do the same as "D" does in the sense that you can slow the car without using the brakes but the ability to downshift in the automatic is also useful for going up long grades in which you do not want to have the car shifting more than necessary. As far as I can tell, the "B" option does not allow you to drive uphill without shifting, especially since the Prius does not have gears to shift. Also, I am not that confused, I just wanted to make sure that if I move the selector **** that I don't blow the car up!

On a side note, the Prius does a great job of accelerating up long grades with curves and flats. It is really nice to not have the engine revving, then shifting, then revving again.

Thanks to all for posting, now Ill go play with "B".

 

Okay then let me say it so "you" understand. Saying it is like first "gear" just lets the general consumer understand it in terms they are used to with normal vehicles. Maybe I should have said B is like a lower type gear. While you may not believe the Prius uses gears it does, they are just variable. The term is still considered in a state of a gear ratio.

My intent was to remove so much confusion over the B drive. If you make things easier the masses will understand it better and may want to learn more before being scared off. To many people here want to over techno the information that it is no wonder more people don't want to drive Hybrids. The phrase, "Keep it simple stupid" is so true.

 

Resist -- For all I know, you could be the guy who invented the Prius and know every in and out or you could have just picked up your Prius last week because it was a pretty color. That is the problem with forums, you never know who you are dealing with and what they know. (Assumptions get you in trouble) I know all about the "gears" or the CVT in the prius and how they/it works. I may have an 07' but I have been around the prius since 01', have done extensive research in the mean time and understand a lot about the prius and other hybrids. I do not claim to know all there is to know, but this thread was originally intended to get a general knowledge of who actually uses the "B" selection, why, and a get a general "when to use it "/ "when not to use it".

I don't think someone who is considering a Prius will be scared of an unknown "B" selection. If they are buying a prius, that would be the least of their worries! Merely adding a line or two in the manual would be helpful to the general consumer instead of just saying "Engine Brake". Changing the nomenclature of what they have on the shifter isn't necessary. To use your terms, "Common sense should take over after understanding this"

Cool?

 

I hear ya.

 

To clarify: The Prius does not have any switchable or variable gears. The CVT is not a belt-type variable-ratio transmission. The gear ratio in the planetary gear (power split device) is fixed. The effect of a variable gear ratio between the ICE and the wheels is obtained by driving MG1 electrically (either forwards or backwards, depending on the car's speed). This enables Toyota to keep the ICE in its low-rev, high-efficiency range even as the car's speed increases. In coasting at speed (which is what I was discussing — you can have coasting with or without fuel-cut; if there's no fuel-cut, the FE gauge shows fuel usage), the ICE must be kept spinning in order to prevent MG1 from over-revving. Either it's using fuel and turning itself over, or else (in fuel-cut mode) it's being turned over by MG1 with electrical power from MG2. In 'D' this is designed to mimic the mild engine braking of a normal automatic transmission car. The ICE is spinning at ~1000 rpm. In 'B' it's intended to provide much more engine braking by simulating the effect of changing to a lower gear in a normal (manual or automatic) vehicle. The ICE is being driven to a much higher speed (~3000 rpm). But no gears are being changed!

Stan

P.S. You can drive uphill (or even on the flat) in 'B' without harm to the Prius. However, it's not recommended for normal driving, since engine braking with fuel-cut is used preferentially instead of regenerative braking with EV mode at lower speeds, and this is wasteful of energy.