Windy road, do frequent switches between B and D hurt anything?

Whether by Toyota design or not, I think B is typically needed when you're on a long downhill, with lots of the same to come, enough that the car will fully charge the battery, cease charging and relegate braking needs completely to the friction brakes, long before you reach the bottom, long enough that there's a danger of brake overheating. The car has no means of making that judgement, doesn't know the topography ahead.

 

Yeah I agree.

Pixel 2 ?

 

Gen 4 has automatic hill keep assist...

 

B mode is required by US law.

CFR2 011 title49 vol6 sec571.102 S3.1.2 Transmission braking effect. In vehicles having more than one forward transmission gear ratio, one forward drive position shall provide a greater degree of engine braking than the highest speed transmission ratio at vehicle speeds below 40 kilometers per hour (25 miles per hour).

In use, you can shift to B from the very top of hills that will need B by the bottom. This will keep both the brakes and battery cooler.

N is also required by US law, but I have no real reason to ever use N.

CFR2 011 title49 vol6 sec571.102 S3.1.1 Location of transmission shift positions on passenger cars. A neutral position shall be located between forward drive and reverse drive positions.

https://www.gpo.gov/fdsys/pkg/CFR-2011-title49-vol6/pdf/CFR-2011-title49-vol6-sec571-102.pdf

 

Maybe..., not that long from now, with the built-in navigation, it will know the topography ahead, how much of an elevation change is coming, and be able to make judgement call regarding B mode. One thing, it still wouldn't know your destination: are you carrying on for miles, or are you likely to stop soon, say even just at a viewpoint.

Right now, seems pretty onerous that the driver needs to make such judgement, it's an odd scenario. A conventional vehicle, with engine constantly running, it's a lot easier to use engine braking, all the way down. The Prius OTOH, quickly becomes fully charged, and without intervention (shifting to B) will become almost freewheeling, requiring protracted leaning on the friction brakes.

 

True - though only in forward direction. Other manufacturers use it in reverse as well.

Many days I use "N" briefly. When I park, I have 2 paving bricks marking where my front wheels should be - any closer forward and I can't open my door properly, too far back I can't open the hatch without it hitting - I've got about a 3" leeway. But if I feel that I've touched the pavers, I put it in "N" and let it roll back so the wheels aren't forced against the pavers all night. Maybe a bit OCD - but I believe some tyres have a memory, at least till they've warmed up.

 

This is the one scenario I'll use Neutral, when parking pointing uphill, and rolling the back of the front tires into gentle/natural contact with the curb:



Sometimes I forget and use Reverse, works out, but Neutral is definitely better.

 

And it WILL......if the cruise is ON.
Is there really an "angle sensor" ?
I highly doubt it.

IF.....your car ever completely stalls out in the middle of traffic......you might find it very useful !!

 

Third gen's with LED headlights have an inclination sensor, mounted on the rear cross beam. Fourth gen I think they eliminated it.

Still, I don't see this being useful: you don't want or need the car switching to B every time there's a downhill, only when there's an extremely protracted downhill. And there's the rub I think: the car doesn't have ESP, know the road ahead, how far you're going.

 

Yes. Several. Alarm, both headlights (in locations with automatic headlight leveling), and very precise accelerometers in each airbag that can determine angles. Not used for anything other than their own systems though.

Pixel 2 ?

 

When B Mode is engaged regen is always used on overrun, but when the battery cannot safely accept more charge, excess voltage is used to turn the ICE without combustion taking place.

It's not just US law that requires B Mode. It's a Toyota feature in all Gen 4 sales territories. The protocol is to have a sort of low gear in automatic gearboxes. I can remember when they used to feature P-N-D-L-R or P-N-D-1-2-R on the shifters.

 

Someone at Toyota was too honest to call it L, it would have saved a great deal of discussion if they had.

 

I think we are evaluating "B" mode as it exists today...in the vehicles, and speculating as to what it could be designed to be tomorrow.

I think the biggest stumbling block or hurdle to any "automatic" B mode system, is that Toyota pretty much recommends using "B" mode for long inclines down extended hills or mountains. IMO it's NOT downshifting, in the traditional ICE manual transmission manner.

It's an "option" because users are suppose to evaluate the situation and implement as appropriate.

While you could probably create sensors and a system that could evaluate the immediate conditions that would make "B" mode preferable, what I think is near impossible would be evaluating the road ahead as a whole.
How would any system know if this is a momentary rolling hill? Or an extended down the big hill or mountain drive?

I never used "B" mode, as the OP in this thread has...for me it was always only on pretty long, down hill stretches, where downhill gravity and momentum was going to be maintained for extended time.
I think it would be pretty challenging, to design an automatic system capable of making that decision.
Challenging but maybe not impossible.

It might be better and easier just to keep explaining to people exactly what B mode is, and how to use it.

When I was shopping/looking at Prius, I played dumb, because I already knew, from experience here, and asked my salesman what the "B" was on the selector.

He gave me a very confident sounding but entirely fictional description of an Inspector Gadget like choice, that supposedly could be used whenever you felt like charging your battery.

I didn't bother correcting him.

Did I ever say it didn't?

 

I agree with that assessment regarding the role of "B", only: Toyota actually says next to nothing on suitable times to use "B". The lore we've built up is through hands-on experience, mostly here at Priuschat I'd think.

This is from page 174 of my 2010 Prius Owner's Manual, US/CDN edition:



And really, that's ALL they say, pretty cryptic.

 

Yeah, now that you post it, that is the vague description I remember.
And Toyota's "Fill In The Empty Spaces" approach, does lead to the questioning, and "personal" definitions and approaches to usage that keep re-appearing.

Bottom line, for me personally, I only used B in long down hill situations.

 

Rolls Royce - 5+ years ago


As an aside - I've been going to ask what does the wind have to do with it? I haven't found my PRIUS all that sensitive to cross winds or head winds compared with other cars I've had. Winding roads - yes!!

 

Gen 4 is similar:

 

You'll soon get over the "watching the Energy Monitor" mode. If I'm bored, I'll put it up again. Or if someone is in the car who is new to hybrids.

 

That's you and me both. My previous car was a CR-V also. My Prius is now agreed 22 months and I'm still enchanted by the energy monitor. No collisions while driving yet either!