Engaging Engine Braking (B) Function

no.

 

But remember this:

1: You are only going to use B when going down a very steep hill and want
to capture more charging than normal, and also to help slow down and save brake pads.

2: Any other non-hybrid that has manual shift, their brake lights will not come on
when they are down shifting to serve the same purpose.

 

And many "normal" cars have significant engine drag. Just lifting my foot off the gas on my Jeep causes a major slowdown - without any brake lights.

Tom

 

there's a HUGE misconception there.. as you're not really capturing more charging than normal when you shift into B.. the engine spins up at a higher RPM and it's primary purpose of doing so is to slow the car down..

it actually WASTES energy instead of recovering it as it would if you were just using the normal brake and have the shifter in 'D'

'B' is used and only should be used on long steep downhills where with all the regenerative braking you would have gotten out of 'D' and just using the brake pedal would have filled up the battery... or the battery is already full..

so to help save the friction brakes.. only do you then use the engine to help slow you down. there are tons of resources debunking this random myth that who knows where came from.

 

Exactly correct. The B position is the same as putting a manual transmission car in gear and releasing the clutch to slow the car down. Because B mode slows the car by spinning the engine and not the electrical generators, the energy is not used to charge the battery.

 

It depends on speed.
The B mode behavior is completely different on a certain speed threshold.
Below 43 km/h on the JP Prius, the B mode does not spin the engine, and we see more regeneration in B than D.

Ken@Japan

 

This comes up a lot, and it's explained in the manual. I used B one time to see how it worked when we first got our 2005 Prius, but noticed that it didn't replenish the battery. The Prius considers B a wasted energy generation opportunity. Energy generated by regen braking = better MPG!

The rest of the time, while we accumulated the 136,000 miles we put on our '05, I used regen braking for hills and any other time I could do so safely. That doesn't use up your brake pads, since the calipers are not put to work at that time. You can get plenty of regen braking power that adds a significant amount of charge to the traction battery, before you push the brake pedal in farther to actuate the heat generating friction binders.

Brake pads on the '05 still showed very little wear at trade-in time this past February. We could just barely feel the transition from regen braking to caliper braking on the '05, but it was there. Not sure if the c allows any feedback through the brake pedal, other than info screen showing the battery filling or not. I don't recall now, since my test drive in the c was too short and almost a month ago.

 

at least for me... i can feel when the friction brakes start to engage.

 

With the NA Gen II, I've had the engine race in B mode at 15 mph, or 24 km/h. This was on a very steep descent, but it did it every time I descended.

Tom

 

Sorry to bring up an old thread, but I figure this question fits here. I didn't find much info regarding engine braking with the Prius C manual. I was wonder besides using it for downhill braking, is it safe to use the engine brake while slowing down in normal traffic or taking curves without using the brake? If there is no detriment to the engine, I'd rather use B to slow down than the brakes to save on pads and to maintain speed with minimal loss through curvy streets in order to maximize MPG.

 

Prius brake pads usually last well over 100k miles unless you do a lot of hard braking. The first part of your brake pedal travel causes the electric motor generator to charge the battery and slows the car.

Think of B as low range on a normal automatic transmission, it's there to maintain speed on long downgrades, not for normal slowing of the car. It works differently but the goal is the same.

 

If it is anything like the regular Prius -- and it should be -- there is no harm to the engine or anything else. But neither is there any useful gain. Unless your brake pedal style seriously defeats regeneration, the pads should already last a long time. And there is no MPG gain, and very likely a small loss, compared to ordinary brake regeneration.

 

I have a Prius C2 with the standard auto shift stick, I guess it's just habit that I like downshifting from my manual driving days!

 

I guess I will have to reread my manual.
Had the feeling it said the opposite.
And the dealer mentioned it too. Bringing up the fact, that using B-breaking the breaks are used less so the car dealers make less money on replacing them on hybrids.

I personally use it daily. When I am at higher speed than I want to break nicely.
The screen which captures the charging absolutely shows the positive effect.
Unless it is of course some malfunction in their computer (or purposefully put lie).

If the car is running using EV engine and there is rotating moment, the latter can be captured by the batteries than dissipated as heat in the breaks. But again - I might be wrong.

 

Yes, it is safe.
It is not in the manual much as it's only productive use is going down long steep grades.
B is not going to save on brake pads, and they will most likely out live the car.
No, you will not maximize MPG in B, at any speed over 24 MPH.

B under the D in the Drive gears? | PriusChat

 

Apart from a few tries soon after getting the car, I don't use B. I've yet to experience a hill that caused the car to quit charging, at least as evidenced by the dash display of charging.

The few times I did try B on a long hill the engine rpm shot up alarmingly. And I understand if left to it's devices the car will do some B mode on it's own.

 

The screen is correct but not showing you the whole story. If you just wanted the additional regen brakes you could have got that by pressing the brake pedal to move the HSI indicator to the same position.

When you shift to B mode, absolutely, the car does increase the amount of default regen braking it puts on, but it doesn't change the maximum amount of regen braking. The thing is, B mode also fires up the engine as well and uses it to throw away energy (by turning it into heat).

There are times where that's an effective thing to do and there are times where that is just a waste. There are some other threads where this has been gone into in more detail... it's worth a read to understand what you're really choosing between when selecting B vs D.

 

As Prius owner from South New Jersey, it is very very flat, I see no benefit of using the B mode. Someday I will drive to the mountains and have an opportunity to use the feature.

 

By doing this, you're losing one of the primary advantages of owning a hybrid: regenerative braking. You'll be using the engine to slow the car down (wasting the energy) vs. putting it back into the battery.