We recently ditched our 1998 Land Cruiser for a 2010 Highlander Hybrid - We live in the mountains and I am regularly going up and down passes. In my land cruiser, I had the option of gearing down...now, I have this B mode on the transmission column. I've used it as I would in my old car, but I hate the sound it makes as it slows the engine down...Although the engine doesn't get hotter, it sure sounds like the engine is revving too high for comfort!! So, I recently discovered, as I descend in B, if I ride the accelerator pedal, it actual decreases the engine noise, yet still slows the car. And the gas engine never engages (Without my foot on the accelerator, the engine tends to slow too much...)

Has anyone else used the accelerator in conjunction with the B mode? I called the dealership and they had no answers for me...I've looked in the manual to no avail...I even sent an inquiry to Toyota.com and they simply said that the B does not over-rev the engine. However, they never addressed my use of the accelerator when in B mode...ANYONE? I would love to know if I'm doing it right as we are in the middle of winter and we've had some lovely icy / snowy roads lately...

Thanks in advance for your help...

 

I use the "B" mode quite often to slow the HyHi down when approaching a traffic light or stop sign. It's like "Braking mode with an attitude" -- since it also charges the battery at (I think) a higher rate (Not so sure about this, but it is how it "feels" when it is engaged).

I also use it for going down hills that are steep so I can maintain speed without braking.

just my .02

 

B mode is "Engine Brake", which basically means the electric engine slows down the car without having to actually press the brake pedal. It is used to brake when going downhill for a long period, to prevent the brakes from overheating. It also helps to recharge the hybrid battery (notice the change on the charge indicator in the electricity gauge).

 

But, is it okay that I ride the accelerator down the hill when in B mode? See, I travel often over a pass that is quite steep for about 6 miles (lots of twists and turns as well...) When I simply put it into B mode, it slows my car down way too much (you end up with people on my tail...)...So, instead of constantly braking, I've kept it in B mode and put my foot on the accelerator; it seems to keep the engine slower, yet allows me to go faster than just in B mode...and without the terrible "revving" sound the engine can make simply in B mode down this large grade...

What do you think? have you tried it?

 

The B mode uses internal combustion engine braking to slow the vehicle when descending a long steep hill. Don't use the B mode for other purposes.

In the B mode regenerative braking is disabled.

Regenerative braking is what increases the fuel efficiency of hybrid vehicles.

A long steep hill will eventually completely charge the battery at which time regenerative braking will no longer be able to absorb any energy. (Some regenerative braking systems have a large resistance load to use when that occurs).

--

 

"...regenerative braking is disabled.."

Only for coastdown periods, apply light pressure to the brake pedal and you still get regen braking.

 

This is one of my disappointments in going from a 1993 Landcruiser to a 2008 HyHi. We live on a 12% grade hill at Lake Tahoe and I do use "B" to slow down the car when there is ice or snow on our road. However, as you discovered, B is too slow when coming down a long highway grade to the Lake from I-80 and I am continually either stepping on the gas or shifting to D and then braking. Toyota had no answers for me either, regarding whether or not gas should be applied in B, so I shift to D when I need more downhill speed and then shift to B when I get to about 45 mph after braking. It sure was nice having the extra low gears on the Landcruiser!

The other big pain with the HyHi is that if you have snow tires mounted on different wheels, with the attendant new air pressure sensors for the wheels, the computer will not save and display accurately the 4 extra wheels. Reno Toyota charges $120 to reset the computer for the new wheels' pressure monitors, while Pasadena Toyota will do it for "only" $110.

 

Kattahow, keep it in "B" and simply modulate your speed with the accelerator pedal - very simple, and not problem at all to the vehicle - it will not over-rev the engine: a little throttle decreases engine braking, while more works in the conventional way, accelerating you.

Keeping it in B in normal driving decreases FE by substituting engine braking (generating useless heat from friction and air compression) for the free lunch of regenerative braking. But on long downhill runs, regen. braking efficiency decreases as the traction battery nears full voltage, and B mode efficiently and safely slows you without brake pad/rotor wear or possible damage or, God forbid, brake failure from overheating.

Pete

 

Why doesn't Toyota put dynamic braking resistors on their vehicles to handle the case when the battery is nearly fully charged?

I have noticed that when my HH battery is nearly fully charged, I have to use more brake pressure to get the same deceleration because of the lack of regenerative braking.

 

I assume because of cost and weight issues, not to mention space taken up by the huge heat sinks that would be needed to dissipate the heat from 45kw (60hp) of power flow. The brake rotors are just that, and probably weigh 100# for the four. They need to work on smoothing the transition from regen to friction braking, though, as the sudden disconnect of regen after a road bump is unsettling at first, to say the least, and scary if you don't know what it is.

One day, maybe a supercapacitor to capture more of this energy along with more efficient batteries.

Pete