How Often Do You Use The B Mode In The Tranny?

[jditom]

When and how do you all use it?

[Rx330driver]

i dont own the car, but its for going downhill. because the hybrid doesnt use regular transmissions, (CVT), there are no gears to help while braking (engine braking). THerefore, the B acts like an engine braking mode, to help with going downhill. it applies a little "engine braking"

[SW03ES]

Yep, its used for situations in which you would "gear down" on a car with a normal transmission, long downhill 7% grades etc to save on the brakes.

You'll almost never have to use it.

[skyfish400h]

When and how do you all use it?

You won't notice that it does much until the rings break in on the engine and the compression comes up... takes a good 1000mi or more to get the full effect. You probably shouldn't even use it until then... goes with the "drive it easy" for the first 1000 mi advise.

But once it starts working, you can use it for decents on steep grades as mentioned here... but I also use it to down shift in heavy freeway traffic so I don't have to move my foot to the brake pedal. Much like you can do in a manual by down shifting, but not quite as effective.

[wwest]

When and how do you all use it?

You won't notice that it does much until the rings break in on the engine and the compression comes up... takes a good 1000mi or more to get the full effect. You probably shouldn't even use it until then... goes with the "drive it easy" for the first 1000 mi advise.

But once it starts working, you can use it for decents on steep grades as mentioned here... but I also use it to down shift in heavy freeway traffic so I don't have to move my foot to the brake pedal. Much like you can do in a manual by down shifting, but not quite as effective.

But keep in mind that this is a FWD vehicle and downshifting to attain engine braking can be fraught with TERROR should the roadbed be unexpectedly slippery. Additionally remember that engine braking can reduce the functionality of ABS to nil...

[bv2]

But keep in mind that this is a FWD vehicle and downshifting to attain engine braking can be fraught with TERROR should the roadbed be unexpectedly slippery. Additionally remember that engine braking can reduce the functionality of ABS to nil...

So, I take this to mean I should never use this when descending a mountain road covered in snow...

correct?

[Rx330driver]

well...i think obviously, you should keep your foot on the brake. That should still engage the abs. use your common sense and you should be fine

[bv2]

But keep in mind that this is a FWD vehicle and downshifting to attain engine braking can be fraught with TERROR should the roadbed be unexpectedly slippery. Additionally remember that engine braking can reduce the functionality of ABS to nil...

So, I take this to mean I should never use this when descending a mountain road covered in snow...

correct?

But does it matter if it is better to be in B or D as you descend slowly and carefully down a snow covered mountain road? I had been taught in the past that low gear in traditional cars/trucks is better than D in this situation-- so does this correlate to my AWD hybrid, no, or is this info incorrect?

[Rx330driver]

im guessing it would be the same...why would it be different just because theres a battery on board

[Jim Nazium]

Bottom line, if you are descending a hilly section and you require constant "foot on brake" to maintain a safe speed to negotiate various turns and sweeps in the road as you descend, then you should be in B mode so as to not overheat the brakes. The engine braking will help in the descent, and keep the brakes in a safe operating temperature and avoid brake fade.

However else you use B mode, I believe this is the main benefit and intention for it.

Cheers,

MadloR

[SOMEONE ELSE'S GOT MY NAME]

Never. It's really putzy compared to the amount of brake drag we get off the prius. We have the AWD so I'd think there would be twice as much ability to slow the vehicle down, despite its greater mass ... but it just aint nearly as much brake power generated ... so we don't bother with it. Using the brake peddle has a much greater regenerative yield.

[jditom]

Bottom line, if you are descending a hilly section and you require constant "foot on brake" to maintain a safe speed to negotiate various turns and sweeps in the road as you descend, then you should be in B mode so as to not overheat the brakes. The engine braking will help in the descent, and keep the brakes in a safe operating temperature and avoid brake fade.

However else you use B mode, I believe this is the main benefit and intention for it.

Cheers,

MadloR

I don't think yout brakes will ever overheat and fail on this SUV. B mode is just another way to generate more electricity (e) to store in your battery. It happens when you coast and in B mode you will make more e out of the system. This was not indented to be used to save your brakes although it will.

Now the big question is how does it generate more e?

Your coasting and not braking so you got some e generating there.

In a lower gear in B on your CVT is the engine also kicking in the generate e?

[skyfish400h]

I don't think yout brakes will ever overheat and fail on this SUV. B mode is just another way to generate more electricity (e) to store in your battery. It happens when you coast and in B mode you will make more e out of the system. This was not indented to be used to save your brakes although it will.

Now the big question is how does it generate more e?

Your coasting and not braking so you got some e generating there.

In a lower gear in B on your CVT is the engine also kicking in the generate e?

Sorry, but this is exactly backwards. The B postion does not regenerate (it uses engine compression so the energy is lost as heat) and you can overheat the brakes on ANY vehicle if you ride them on downhills.

[Jim Nazium]

I don't think yout brakes will ever overheat and fail on this SUV. B mode is just another way to generate more electricity (e) to store in your battery. It happens when you coast and in B mode you will make more e out of the system. This was not indented to be used to save your brakes although it will.

Now the big question is how does it generate more e?

Your coasting and not braking so you got some e generating there.

In a lower gear in B on your CVT is the engine also kicking in the generate e?

Sorry, but this is exactly backwards. The B postion does not regenerate (it uses engine compression so the energy is lost as heat) and you can overheat the brakes on ANY vehicle if you ride them on downhills.

Bingo! Couldn't of said it better myself.

[Colo Springs RX400h]

Going down mountain roads, I use the B position. It keeps you from having to hold your foot on the brake for the entire decent.

You all are more mechanical than me. But when I look at the guage on the left and put the transmission into B mode, the gauge moves into the "Blue" zone which shows that it is generating electricity. Also, adding brakes to the B mode gets you farther into the "Blue" zone than just brakes. Are you sure the B mode has no generating capacity?

[skyfish400h]

Going down mountain roads, I use the B position. It keeps you from having to hold your foot on the brake for the entire decent.

You all are more mechanical than me. But when I look at the guage on the left and put the transmission into B mode, the gauge moves into the "Blue" zone which shows that it is generating electricity. Also, adding brakes to the B mode gets you farther into the "Blue" zone than just brakes. Are you sure the B mode has no generating capacity?

Just taking your foot off the accelerator will produce the same behavior in D as well.

It's the portion of the regeneration that would come from the brakes that is replaced by the engine and therefore does not re-charge the batts.

[jditom]

So before we bought our 400h 2 salespersons told us that B will recharge the batteries faster?

I have read the manual and can find no such mention of this

[jditom]

So before we bought our 400h 2 salespersons told us that B will recharge the batteries faster?

I have read the manual and can find no such mention of this

OK so I went for a drive with 2 small hills of about 3-5% decline. Both times I was in B mode and each time I did this the power meter dipped in to the blue area. And both time I was able to charge the batteries into the green. This has never happened before, my battery charge color is always blue.

Anyone know how this is occuring? Looks like increase charging to me.

More to follow

[w@ntonsoup]

My guess is that in "B" mode (engine braking), although regenerative braking is deactivated, perhaps electric assist is too - meaning you're running on 100% engine, and generating electricity at the same time.

So... charging the battery but burning more gas.

[skyfish400h]

My guess is that in "B" mode (engine braking), although regenerative braking is deactivated, perhaps electric assist is too - meaning you're running on 100% engine, and generating electricity at the same time.

So... charging the battery but burning more gas.

again, its the braking regeneration that you are losing out on the B postion. the normal "foot off the acc" regeneration occures in either D or B.

[Colo Springs RX400h]

Try the following. I did and it sure looks like the B position increases electrical generation.

Going down hill in D, watch the gauge on the left. Then put the transmission into B. The gauge moves immediately into the "Blue" zone (generating electricity).

Then going down hill in D with brakes engaged to slow - not stop, watch the gauge again. Now, shift to B again with no change in brake pressure. I think you will see the gauge move further into the "Blue" zone when you shift to B.

Either the gauge doesn't show what it is supposed to show, or the B positon does increase electric generation.

[jditom]

B mode is somehow using the engine/cvt to generate more power.

Every time I use it for more than 30 sec I can charge my battery to the green level which I have not done in D. And as stated your power meter dips into the blue.

[raleedy]

When and how do you all use it?

I never use it. In a car without regenerative braking, engine braking spares the brakes. In the hybrid, it seems like it just reduces the regeneration. So why do it?

[jditom]

When and how do you all use it?

I never use it. In a car without regenerative braking, engine braking spares the brakes. In the hybrid, it seems like it just reduces the regeneration. So why do it?

If you read the post above folks are saying that you can generate more power to store like reg braking.

[w@ntonsoup]

I don't think that's true, read my post. I think it just doesn't USE the battery up when in that mode, but it doesn't CREATE battery power either.

It's for use when driving down steep declines, like down from the mountains, to save on your brake pad wear.