Using "B" gear on shifter

Excellent answer FireEngineer. There is no reason not to use "B" to slow down in traffic, particularly if not using it (gently braking instead) will bother other traffic. "B" will shorten your slowing distance. Just remember to switch back to "D" once you have finished slowing. I don't see how it alone could reduce mileage if used properly. That is, you would be "keeping up with the obsolete vehicles around you re slowing and speeding up unnecessarily rapidly." If you drove like that in "D" you should get the same mileage.

I used to shift the anti-Prius (2001 Pathfinder) to 2nd gear for slowing down. That puts extra wear on the transmission, and is "not recommended" for "ordinary" vehicles. "B" just changes the control points in the software on the Prius. No extra wear, no problem.

 

That 2nd picture is from Westbound I-70 headed down to Dillon isn't it?

I use B whenever I'm coming down a mountain grade. It does charge up the battery rather quickly and makes driving easier because you don't have to constantly use the brake pedal.

Say, regen braking only ocurrs at the front wheels doesn't it? So the regen brakes and B mode both only apply resistance to the front wheels. Does ABS work with regen? hmmmm

 

<div class='quotetop'>QUOTE(David Beale @ Jun 1 2007, 02:30 PM) [snapback]453438[/snapback]</div>

But remember that if you shift into "B" above 20MPH the ICE will spin and may be using gas to do so, at the very least you'd be using battery that you have to replace later via the ICE/gas. If you're intertested in maximum regen your foot modulating the brake will generate more than "B". Also, many people who are interested in maximum MPG would say to glide the extra distance instead of "braking" in some way.

<div class='quotetop'>QUOTE(tanglefoot @ Jun 1 2007, 03:22 PM) [snapback]453492[/snapback]</div>

ABS only occurs with the mechanical brakes, you would have to press the pedal a certain amount to engage the friction pads. Or, if you press quickly on the brake pedal, the stroke simulator in the brake system thinks you want to stop NOW and does not let regen in (or kicks it out), but ABS is ready with your friction brakes. Since "B" is just a software forced regen the above apply when your in "B" mode as well. However the wheel spin sensors are always active, try going over some uneven terrain, like an angled railroad crossing, under regen and if different wheel speed is detected the regen is kicked out and your friction brakes are ready to use with the ABS.

Wayne

 

Ahhh thanks...makes more sense now.

 

<div class='quotetop'>QUOTE(FireEngineer @ Jun 1 2007, 12:57 PM) [snapback]453518[/snapback]</div>

If the ICE is running in B mode, why does the MFD read 99.9mpg when going down a steep grade, even after the battery is fully charged? Doesn't the sensor monitor fuel being used by the ICE, and therefore would report if fuel was being used by the ICE and would reflect that on the MFD by displaying less than maximum mpg? This is why I don't understand the argument that you lose mpg when in B.

 

<div class='quotetop'>QUOTE(jbullard @ Jun 1 2007, 04:16 PM) [snapback]453535[/snapback]</div>

The MFD does not give you an exact condition of what is happening, it's not an instrument, it's more of a guide. Besides even if you are using VERY small amounts of fuel the MFD still will approximate it to 99.9 for anything over 100MPG, just look at some of the posts from the ScanGauge/CanView users. Same with gliding-no arrows-your really using 5-6 amps of battery, not zero.

Wayne

 

I wouldn't say "never use B mode" there are certain times when you can use it. I don't know about the adverse effects of using this mode all the time is but I think using it sparingly and when needed will help. Semis use this method of breaking often and even when entering into smaller towns I see signs "No Engine Breaking" I guess that applies to me now too!

Also, has anyone with a CAN-View tried to see if regen is affected at all by throwing the car into B-mode?? I have read differing opinions on the subject some say regen does occur others say regen doesn't occur, so I'm sure the CAN-View could tell us what is really happening.

 

I'm picking up my Prius tomorrow, but my take on the B mode is that it serves the same purpose as downshifting in a regular car: it keeps the friction brakes from overheating. Light or moderate use of friction brakes will get them red hot on a long downgrade and could cause them to fail.

 

<div class='quotetop'>QUOTE(kdk84 @ Jun 1 2007, 05:16 PM) [snapback]453580[/snapback]</div>

If your on a flat road and take your foot off the gas from say 40 MPH, coasting regen will be from 5-9 amps. If you throw it into "B", all things being equal and the battery can take a charge, regen goes up to about 13-20 amps. If you use your foot on the brake properly instead of "B" you could generate over 30 amps. Always if your over 20 MPH the engine will spin.

Wayne

 

After more testing today, engaging "B" when coasting to a stop can start the engine spinning (but it doesn't always do so - more testing needed). Regen is still working in "B". Even the MFD shows that. The engine spins with no fuel (what I saw - using my Scangauge), but it does spin to bleed off energy, energy a portion of which you -could- have recovered via regen. Or perhaps not. I have no way to tell if the friction brakes are working.

I wonder if there is any way to monitor them?