[bokuwasaiko]

I'm curious.... since the Prius has an electronic shifter instead of
the traditional kind, is it possible to accidentally shift into
reverse or park while moving like you can in a real car (I only did it
once ) or does the car know it's moving and prevent you from doing
this?

Also, with regular cars you're supposed to shift into neutral when you
know you're going to get towed. How do you do that in the Prius when
the car's off?

Also, I heard from the dealer that "B" was for going under battery power. I heard on the 2004-prius Yahoo group that it meant something else, but nobody said what. What's it mean? "Backwards?"

thanks

Matt Dukes

 

[frenchie]

Also, I heard from the dealer that "B" was for going under battery power. I heard on the 2004-prius Yahoo group that it meant something else, but nobody said what. What's it mean? "Backwards?" Smile

Can't answer the first questions, since I don't have a 2004 Prius. But concerning the "B", well, first... never go back to this dealer again. He'd rather sell umbrellas than Priuses. :roll:

"B" stands for "braking" and is used to provide the car some engine braking like in a conventional car with manual transmission. This is useful for long and steep descents, for instance driving down a pass, because it makes you use less brakes than in the "D" position. However, as it increases mechanical friction it should not be used all the time because this can decrease your gas mileage. Remember that in a Prius, even the brake pedal does not engage brakes necessarily, it only sends a signal to a computer which will try first, if the deceleration is moderate, to use an electric motor (being at this time a generator) to slow down the car. So, if you apply moderate and constant pressure to the brake pedal while driving downhill in "D" position, you will mostly convert energy into electricity, not in heat like with conventional brakes. Which means also more security and less brake pads wear. Another very "cool" feature of the hybrid concept... 8)

 

[efusco]

I'm curious.... since the Prius has an electronic shifter instead of
the traditional kind, is it possible to accidentally shift into
reverse or park while moving like you can in a real car (I only did it
once ) or does the car know it's moving and prevent you from doing
this?

It knows and won't allow it to happen. You must be stopped or nearly stopped to shift gears.

Also, with regular cars you're supposed to shift into neutral when you
know you're going to get towed. How do you do that in the Prius when
the car's off?

The front end MUST be lifted off the ground--there is a tow hook attachement for that purpose.

Also, I heard from the dealer that "B" was for going under battery power. I heard on the 2004-prius Yahoo group that it meant something else, but nobody said what. What's it mean? "Backwards?"

It stands for engine Braking. Shifting into that engages the electronic motor to brake--recharging simulataneously.
--evan
[/quote]

 

[patrickg]

[ OK, guys, lets take another run at what the shifter "B" position means.

One says engine braking (gas engine I asume) and the other claims regenerative braking.

I hope it is regenerative braking. I wonder if stop and go city driving would be better in "B" ?

...and while on the topic of braking... I wonder what the "formula" is that determines how much regenerative braking you can get before friction braking starts.

Pat

 

[nmpriusman]

"B" mode stands for engine braking. The Hybrid System automatically uses the regenerative braking, and in fact, the vehicle will be able to recharge better in "D" (Driving mode). "B" mode is used for coming down steep grades or any other case where additional braking is needed. :wink:

 

[RSnyder]

Although it should be towed with the front wheels off the ground, it is also possible to put the Prius in "Neutral" for slow things like car washes. The gear selector(s) in the Prius is/are completely computer controlled. In the 2001-2003 models, the P position mechanically engaged the parking pawl, but in 2004, the computer even handles this, only when it is safe to do so (i.e. when the car is fully stopped). For Neutral, the computers stop active control of the motors as soon as it is safe to do so. This lets the wheels and engine freewheel independently. The engine may shut off when in Neutral, but it will never start in Neutral. If you shift to Reverse while moving forward, the motors will try to oppose the forward motion, thereby acting as brakes/generators. Similarly if you shift to Drive while moving in reverse. Since in no case do actual gear ratios or engagements change, there's no chance of mechanical damage, with the sole exception of putting a 2001-2003 Prius in Park while moving.

Since you're supposed to maintain good control of your vehicle at all times, you should not go experimenting with changing to unusual gear settings. You will lose the accelerator as a control mechanism. Just
rest easier knowing that if it's accidently nudged into N or R while driving, you can just put it back in D with no ill effects on the Prius (provided you don't lose control and crash due to the sudden excitement, light braking or loss of accelerator input).

Note that even in Neutral, the larger motor spins with the wheels, so it acts as a light brake/generator. This is why you should definitely make sure the front wheels are off the ground when towing after an accident. If there's any exposed parts of the high voltage wiring, the generator effect could produce dangerous voltages there. At least that was true in the 2001-2003 model. I haven't confirmed it for the 2004. In any case, the battery is isolated from any exposed wiring by several relays after an accident or when the computers detect any leakage current. So the only danger would be if the Prius was towed with the front wheels on the ground.

 

[patrickg]

"B" mode stands for engine braking. The Hybrid System automatically uses the regenerative braking, and in fact, the vehicle will be able to recharge better in "D" (Driving mode). "B" mode is used for coming down steep grades or any other case where additional braking is needed. :wink:

Yeah, I get it. If B is engine braking that must imply that the Prius freewheels (as regards the gas engine) when coasting. That would boost mileage. It is always possible that the Toyota engineers "biassed on" the regenerative braking just a little bit to give the car a little bit of drag so it doesn't completely freewheel when coasting as that might be disconcerting to many drivers who are used to compressive braking from the gas engine.

Diesels have the intake wide open all the time, they don't have compressive braking like a gas engine. This neccessitates exhaust brakes on light trucks and "Jake" brakes on big rigs. Some Merceded sedans driven in mountains a lot have had exhaust brakes retrofitted.

I think it would be handy to have a selectable indicator, audble, visible, or both that lets the driver know when they are engaging the friction brakes. I would want to plan stops ahead when able and use regenerative braking as far as was practical without getting into the friction brakes. Likewise going down hills if the grade isn't too steep or prolonged as to require frictiion brake assist.

My old habit, honed with conventional vehicles, has me coasting a good distance when approaching a stop. This "bleeds" off energy to various loss mechanisms including drag. It would seem that with a Prius you'd want to coast less, in favor of regenerative braking instead, i.e. maintain normal speed a little closer to your intended stop and use regenerative braking to recoup the remaining energy (that I would have dissipated to various frictions to avoid more than the minimum friction brake application.)

Like transitioning from powered flight to soaring planes, there are many similarities but also many subtle differences.

Now if only my dealer would hurry up and get me a PRIUS!

Pat

 

[efusco]

Yeah, I get it. If B is engine braking that must imply that the Prius freewheels (as regards the gas engine) when coasting. That would boost mileage. It is always possible that the Toyota engineers "biassed on" the regenerative braking just a little bit to give the car a little bit of drag so it doesn't completely freewheel when coasting as that might be disconcerting to many drivers who are used to compressive braking from the gas engine.

That is, indeed, what they do--you can observe that on the Energy screen as regeneration.

I think it would be handy to have a selectable indicator, audble, visible, or both that lets the driver know when they are engaging the friction brakes. I would want to plan stops ahead when able and use regenerative braking as far as was practical without getting into the friction brakes. Likewise going down hills if the grade isn't too steep or prolonged as to require frictiion brake assist.

Me too. I think on the Classic the transition from Regen to Friction was palpable, on the '04 the change is subtle and I have rarely felt it. At least for learning it would be nice if there was some indicator of when the Friction kicks in.[/quote]