I thought it was, then thought someone said it wasn't and now read on other sites that it is.

I am driving a very long, steep grade soon.

 

There was previous discussion about the B setting

https://www.greenhybrid.com/discuss/...-b-gear-17688/


Being a old manual transmission user, I use it where I see the need to gradually slow down. If I recharge the battery in the process, so musch the better.

 

Yes, B gear is for engine braking when going down hills.

The confusion may arise when considering the effect on total fuel economy and regen. On long steep grades I would err on the side of safety and use B, even if it don't fully take advantage of all the 'free' energy (or paid for energy when driving up the hill).

(start irony) If you want full economy advantage, top off the battery with regen, then coast in N all the way down. Don't stop until the car rolls to a stop! YMMV (stop irony)

T

 

"B" forces the ICE to stay engaged, with the fuel cut out. Normally the ICE section of the Power Split Device would be allowed to freewheel while coasting downhill. The other explanations are correct - it's for slowing the car on a downgrade without the need to ride the brakes. Much like taking your foot off the gas in a manual.

 

is there a speed limit on when you should engage it? I use it on secondary roads but was curious is I should use it on the highway. At higher speeds it can be pretty loud and sounds like I should not use it. I know you guys know how it works and can advise me.

 

You should be using it when you are on steep hills. i.e. coming down a winding mountain road. It's intended for lower speeds (sub 40mph) when the ICE would normally disengage.

 

I've used B gear at speed much higher than 40...like 60+. I didn't think it would hurt the engine or transmission. The ICE does rev pretty high.

Please let me know if using 'B' is bad for the car at such high speeds.

 

Coasting in 'B' mode spins the ICE (without burning any fuel) in order to apply engine braking. As such, it's wasteful. I'd advise as follows.

• If gentle braking in 'D' will allow you to control the car's downhill speed, then use it as a first choice since it regenerates the excess energy into the NiMH battery — notice the arrow from the wheels to the battery — and doesn't wear the brake pads.
• Once the NiMH battery is "full," regenerative braking must be stopped, and the brake pads will come into operation. This is a lossy process; you're now dumping the car's energy into heating the brakes, as well as wearing your brake pads away. Under these circumstances, it's better to use 'B,' and so dump the excess energy into spinning the ICE; it's also wasteful , but at least it doesn't wear your brake pads.
• 'B' mode will also regeneratively charge a non-full NiMH battery at a higher rate than 'D' mode does — that is, it will provide greater deceleration. Note that you can control the amount of deceleration by modulating the accelerator while in 'B,' just as you can in 'D.' If you press the accelerator a bit more, electrical and/or ICE energy will start to flow to the wheels, and the car will behave just as it does in 'D.' It's only when coasting in 'B' that the behavior is quite different from 'D.'
• You can't damage the car by switching into 'B' at speed. There are no gears to be switched. It's only the control algorithm that is changed.

Stan

 

opps n/m

 

w/o burning fuel?


thanks for the explanation, I will still likely avoid B when traveling at highway speeds.