Using "B" vs riding the brake to stops

Your right, there dead wrong, useing the normal brakes charges the battery way better than using the B selection, it uses the ICE like a air pump to "WASTE" energy.

Don't they understand if the B mode got better mpg Toyota would have made that mode normal? Or maybe your friends are smarter than Toyota?

 

Good news, while you are right and they are wrong, they actually have someplace to use B mode in AZ. You want B mode whenever you are going to decend more than about 600 feet, as MG2 can fill the HV battery with 600 feet of drop. If you did not have B mode and the battery was full, you would only have the brakes to slow you down. With B mode you have another way to waste energy besides the brakes, you can use the engine as an air pump.

kitt peak - Google Maps

[ame="http://en.wikipedia.org/wiki/Kitt_Peak_National_Observatory"]Kitt Peak National Observatory - Wikipedia, the free encyclopedia[/ame]

As you can see, 55 miles outside of Tuscon is the Kitt Peak National Observatory, 26 telescopes at just under 7000 feet. Driving back down to Highway 86 at 3000 feet will be a fine use of B, if they just HAVE to use it.

B mode has a counter-intuitive sound, backing off the throttle can make the engine run faster, pushing on the throttle can make it brake less, so the engine slows down. Not what you expect from the 'go pedal'.

 

As a further point of clarification, with or without B mode, once the HV battery hits the high limit the Prius will use engine braking to help slow down. Shifting to B mode tells it to start engine braking now, and not wait for a "full" battery. Potentially this can save some wear and tear on friction brakes for steep descents.

Tom

 

Just tell them to RTFM.

 

You don't get anymore power from the Power mode than you do from the ECO mode or the normal mode (ECO or PWR not selected). The difference is in the throttle response during about the first half of pedal travel. PWR provides a faster rate of change as you push the pedal down; ECO gives you finer control. Normal is in between. All three modes give you the same amount of total power when you ask for it, the difference is where the pedal is located when it happens. Full throttle is the same in all three modes.

The power mode seems to have been provided to make the car seem more like a non-hybrid for new owners. I think a lot (maybe most) cars give you more throttle during the first part of throttle movement. This is done to make the car feel "snappier" to uninformed drivers. Most experienced hybrid drivers seem to prefer ECO or Normal because of the finer control of regenerative braking and acceleration.

I have had my car on some very steep hills and mountains in the Southwest and in Colorado and just kept it in ECO all the time, no problems and very drivable. As previously stated "B" mode is seldom (or never) needed.

 

Oh my goodness, haven't you heard the news?
:focus:

 

good info

 

I use B mode in my gen 2 Prius all the time to slow down the car. The reason I use it is because of all the pot holes around here near the stop signs and stop lights. What happens is below 20mph the engine wont spin when using B mode. Now if I go over a bump with my brakes on traction control might detect a wheel slip and kill regen. If you use B mode to slow down over those bumps you wont loose regen. Thats how and why I use it.

 

Does this mean that if I am braking so quickly that I exceed the recharge capacity of the regen braking (not if the battery is full but rather just braking briskly) that the car will always use engine braking PLUS the friction brakes? Because I'm pretty sure that often when I slow the ICE has completely stopped, so if it's not moving it wouldn't be able to engine brake. Or, is it such that when the computer tells me the ICE isn't on it can still be on it's just that no fuel is going to it?

 

I thought b mode kills regen completely? using b mode because the use of brakes over a pot hole might kill regen sounds wrong to me. Am I missing something?

 

Nevermind....I just decided to RTFM

 

i read the link that Paradox posted for 'B' braking. I still don't understand how it works.

 

No. Regenerative and friction braking. Hence B-mode, to use ICE pumping instead of friction brakes to slow the car down on long descents. Note that if you step very quickly on the brakes (emergency braking let's say), only the friction brakes will kick in (no regenerative braking).

My understanding is that the HSI lower limit of the regenerative braking zone represent the point where friction braking gets into effect in a substancial manner, turning kinetic energy to heat, instead of regenerative braking charging the batteries. You should then rather plan your braking distance to keep you inside the regenerative braking limits as shown on the HSI.

 

As far as I know, and this may be different for the Gen III, automatic engine braking starts when the HV battery hits the high limit, but not when the maximum regen limit is reached. When engine braking is in operation you will know it. The engine makes a sound similar to a small turbojet engine.

B mode does not kill regeneration. It does start immediate engine braking, but regeneration and friction braking continue as normal.

Tom

 

Also true in the Gen3.

If the battery is less than full when you hit max regen (over 100 Amps) friction braking starts in addition to regen just as it does on the Gen2. When the battery is at max charge you get engine braking vice regen.

 

The rest of qbee42's answer matches my GenIII experience --

This is true most of the time, but I've caught a quiet engine braking mode a few times.

At low speeds on slight downhill grades, when D mode regen drag is enough to control speed and ICE RPM is zero, a filled HV battery will initiate engine braking mode. But at this light drag, the RPM is very low and the engine remains nearly silent. Without a ScanGauge I likely would have missed it.

But the vast majority of engine braking brings that small turbojet or giant vacuum cleaner sound.