Using the B gear in town, oversold Prius?

Your usage is correct. The doctor is reducing his fuel economy by using "B" at stops.

"Oversold"? They are very popular now and Toyota can hardly make them fast enough.

 

I second this opinion.

 

When I first got my Prius I too, tried using B to slow down at lights. My thinking was that since there was a greater "breaking feel" that it must be charging the battery more. WRONG! It is just wasting energy by spinning the ICE. No charging advantage at all.

And since the breaking is dynamic and only uses the pads when the car is almost stopped, he isn't saving anything on pad wear. After those first few days, the car has never seen B mode.

Bob

 

I know someone that uses the B mode for exactly the same thing. Even before I new anything about the prius I thought it seemed odd. My thought was "isn't the Prius with all its computers supposed to recapture energy automatically?" I did read somewhere that B mode acts a little differently on the new models but don't know how. Can someone confirm?

What...!!! they actually have one in stock? Better go buy it or you'll be waiting 2-3 months. I hunted everywhere for one. With $4 gas they are more popular than ever.

G

 

I am glad you asked about "B" position. I have rental Prius for last 3 days in Sarasota. Tried to use "B" coming to red lights and can't see or feel any difference between "D" and "B" positions. In both positions I see el. motor charging up the battery (green arrow).
Does anyone has expert explanation of "B" usage?? It looks like many people think it is this way or another but nobody knows for sure.

In regards to availability I stopped at (only) Toyota in town and salesman told me that they are not taking deposits or anything. He said that they are getting cars on "eye dropper system", 3-5 pieces every 4-8 weeks and never know which color or package it will be. You sing up for car and when cars are available they give you a call. Price is MSRP, you want it, you take it, otherwise they hang up and call next person. You can imagine that there is no choosing of this and that either. Sad but true ....

 

Japan, as with OPEC and the major oil companies, really know how to play supply and demand. Besides, does it make sense to keep building 08s (normal production levels) when the 09 is on the horizon? Seems to me, to build demand for the 09s, cut production on 08s. In March I thought I'd wait until late May-early June to order mine. Glad I decided to look in late March. Didn't get the exact color I wanted but am very happy with my silver pine mica w/bells and whistles!!!!!

 

Zach, search here for B-Mode and you'll find all the information you could want. B is for extra engine braking and rarely needed, certainly not in Florida, unlikely in Toronto.

 

I think B stands for brake.

AFAIK, the only time it makes sense to use B is when:
(1) You are going downhill, and
(2) You are going too fast for your comfort, and
(3) You would have to use the brake pedal hard enough that the brake pads are being used up.

So, IMO, it's really just to save the brake bads (and prevent your brake fluid from overheating on a REALLY long and REALLY steep hill like maybe Mt. Washington.).

You'd use it just like you'd use gear 2 or 1 on an auto transmission going downhill.

 

IMO, In Canada it makes sense to keep making 2008's available as long as possible. We lose our $2k Federal incentive on 2009 or later models, but purchase of an 08 can take place as late as spring 2009. Makes me wonder if Toyota Canada will keep shipping 08's later than they would otherwise.

I will continue to assert, until I see evidence otherwise, that Toyota is limiting US shipments because they don't make as much in US as in some other markets such as Canada. Prii can be exact ordered in 2-3 weeks here and some dealers have some limited stock, but they do go fast, given that our gas is the equivalent of $5-6 per US gallon.

 

Try this.

 

Just read it. By far most comprehensive explanation of the B mode. Thanks!

Gets you wondering, why not extra batteries to take advantage of regeneration process?

 

Cost and weight. Extra batteries make nearly zero difference for normal driving, unless you go with a plug-in recharging system. For braking, the only time extra batteries would help is on very long and steep hills - most users would see no gain, while paying more.

Tom

 

I tried B mode going down a steep grade near my home and it works just like a Jake brake; kicks in when you completely let off the acc. pedal (without the noise!)

Having said that, by just using normal service brakes, I tried slowing to make a hairpin turn about midway down the same grade, then stopping off the road to feel the temperature of the Prius front rotors...not even warm! Every other car or truck I rode down the same hill had rotor temps ranging from warm (normal) to hot (hard braking or full loads). The regenerative braking system really seems to be doing a great job so far with these hills!

 

Just want to clarify: Are you talking here about two different experiences? One is going down a steep grade in B mode and the second is where you left it in D and then checked the temp of the rotors?

I am assuming this is the case, because if you were using the B mode, then you would be avoiding regen and would see higher use of the brake pads. While staying in D mode you will be maximizing regen and minimizing (even avoiding for the most part) use of the physical brakes.

 

This is mistaken. The whole point of "B" is that it helps *avoid* use of the friction brakes by using the engine as a brake. The friction brakes should indeed be cooler when using "B".

 

Too true, Richard. Thanks for catching this. I was typing one thing and thinking another. The "D" and "B" in my final sentence should be switched.

If the driver were not going down a steep grade, though, it really would make no difference, except that the B mode may recapture less of the regen than the regular D mode. The D mode does a great job of recapturing energy through regeneration, but by engaging the B mode in steep decents, the system allows more energy to be sent to the battery at a faster clip. I suppose the reasoning is that the flailing engine (talk about a "heat pump") does a great job wasting energy pretty quickly so the batter is better protected.

Hobbit's explanation is excellent, and he makes further reference to other discussions about the total braking system and the use of the B mode. I haven't driven my Prius within eyesight of any mountains containing a steep and long enough grade for B mode to have any value to me. The only value I can see is to allow me to avoid heat fade on the mechanical brakes.

 

at certain speeds and conditions, B is a jake brake.

at low speeds B gear keeps the engine running via the electric motors, right? don't you drain the battery if anything?

if you wanted more of a charge.. hold the break and push the gas. the car regens off the free spinning ice.

some used to say engaging B below 29 (assuming off of EV engage mode) will engage the motors.. but that was dismissed later on via scanguage. the systems generates 5% less while in B mode while braking.

 

I didn't think Priuses have disk brakes. Brake pads go on disk brakes. Drum brakes have brake shoes. Am I right or wrong?

 

A further clarification: the brake pads should be cool in either B or D, unless the size of the hill and the SOC of the battery were such that the Prius had to abandon the use of regenerative braking. As far as braking is concerned, B and D modes work pretty much the same. The real difference is in the final use of the regenerated energy. In D mode it goes into the battery. In B mode, some of the energy is burned off as heat by spinning the ICE. Otherwise the differences are small and technical, dealing with control setpoints.

Tom