Will extended engine braking harm engine?

Engine braking as the name implies uses your engine to slow down the car. It does this by revving the engine. The momentum of your speed is used to speed up the engine. Yes, it decreases engine life. It's the equivalent of someone who stomps on the gas pedal at every light.

Why put it on the car if its bad for the engine? As you've already noticed, it works pretty well slowing you down in the snow on an incline. On steep inclines your would be riding your brakes to slow down. Eventually the brakes would overheat and fail. B takes always some of that stress on your brakes. On a steep incline, you need as much help as you can get to slow down. I'd much rather harm the engine than lose control of the car.

Don't drive with B on. It wastes gas. The only situation I use B is when I face downward in a steep incline.

 

I would use B as often and in the same scenarios where I would use L in an automatic. (ie. not often)

The good news is that when you begin using B for long descents and low traction driving only, you gas mileage will improve. The computers will still use engine braking when they deem it advantageous, but will far more often decide to use regenerative braking, which neither 'uses up' the friction brakes, nor 'uses up' the engine.

Here is a link to how I think the brakes work: B under the D in the Drive gears? | PriusChat

Try D mode and see if you don't get much better gas mileage and even less wear and tear.

(Never trust anything a car salesman ever says. Diane Whitmore is the exception that 'proves' the rule)

 

I do not see any benefit from keeping the vehicle in 'B'.

 

Your Toyota salesman is not alone in his belief. Ours gave us the same advice when we picked up the car.

I see no harm in your having used it--you just missed some energy recovery opportunity.

 

I strongly disagree with this. Using B doesn't engage the gas engine in 99% of cases. It seemply engages the regeneration system. No harm comes from this other than the car is going to have more braking when you're off the throttle, so the car won't coast as far. This will likely reduce fuel efficiency. As many in this thread said (including the person I quoted), use the B setting when going down steep hills in order to not have to press on the brake pedal.

 

Not sure why you're nitpicking. I didn't say using B engages the engine. I said engine braking uses the engine. Besides, you agree with me she shouldn't drive in B to maximize fuel economy. What's the point in stating this? I can easily say, 99% of the time? Really? It's more like 90% of the time with me. What's the the point?

 

I don't want to get off-topic and into an argument. sorry if it came across as nittpicking. My point is that it's nothing at all like "stomping on the gas at every light."

 

+1, i tend to coast and with B it feels like I am braking all the time. it's great for going downhills when you don't like extra accel.

 

There is really no link between B on the Prius and L on other cars. L increases torque to the wheels by changing the gear ratio in the transmission, at the same time lowering the drive wheels RPM relative to engine speed. B doesn't do any of that. Driving in B, except for longish downhill segments will lower overall mileage. The "drive in B" from salespeople is common, and comes from an ignorance of how the synergy drive works. The system is designed to be driven in D...the GenIII cars also have Eco and Pwr modes if you see the need to fine tune anything. For the record, I drive in Eco year round.

 

Both L and B are attempts to comply with FMVSS 102 'S3.1.2 Transmission braking effect. In vehicles having more than one forward transmission gear ratio, one forward drive position shall provide a greater degree of engine braking than the highest speed transmission ratio at vehicle speeds below 40 kilometers per hour (25 miles per hour).'




Standard No. 102; Transmission shift position sequence starter interlock, and transmission braking effect. - Federal Motor Carrier Safety Administration


You can't sell an automatic in the US without a gear with more engine braking than D. But you can call it whatever you want.

 

First, you won't harm the engine or shorten its life using "B"! I wish this myth would stop! In "B" when the engine is used for braking no fuel is injected. This dramatically reduces wear on the engine, even if it is reving up a bit more than normal. In fact, it may actually -clean- the engine a bit.

You WILL get slightly lower mileage using "B".

Finally, just how long do you want the brakes to last? Prius brakes will last at least twice as long as those on a "normal" car. In fact they often suffer from corrosion damage before they need to be serviced due to wear.

Use the car in whatever mode you like, but the car was designed to be operated in "D", with "B" used for descending long hills. You will get the best mileage this way, and other systems, such as cruise control, will work better.

 

Your engine will be just fine! don't worry! Drive and Enjoy!

 

As an added benefit, your cruise control will work in D. It doesn't work in B I found out the first day I had my Prius.

 

B is a blunt instrument, an On/Off switch where a volume knob is called for. Using B is unnecessary for braking except in one circumstance: you are on a long descent and the SOC of the HV battery is high.
You are better to learn good braking technique. With good braking, you will:

• maximise regenerative braking
• use the brake pads and disks only when needed to stop and remain stationary
• use the engine for braking only when the conditions require it.

As a general rule, filling the CHG portion to the left of the HSI display means that you're maximising regenerative braking. At low speeds, say 25km/h - 15mph, the brake pads and disks are engaged; you may barely notice the transition. And if you really need to stop, the brake pads and disks (and ABS) do the job.

If the SOC is high, because of your superior braking and pulse & glide technique, and you are faced with a long descent, then use B. By turning the engine it protects the battery from overcharging. (And if you don't select B, it will turn the engine to protect the battery if it feels the need.)

 

Why in snow?

I fully understand when going down hills. But I do not see an advantage when on snow/ice.

Thanks

 

I really don't understand why Jake-braking is so horrible on a motor....but I'm a layer 1/2 guy so perhaps one of you "really smart" people can break it down for me.

First of all....I get the fact that "B" mode in a Prius isn't really engine braking. Priuses have CVTs and there's a zillion lines of software code between your right foot and the throttle body....so your chances of over revving the motor are exactly the same chances of me retiring as a Fleet Admiral.
Let's forget about fuel efficiency for a second and look at "engine braking".
Yeah. I know.....It's like asking an alcoholic to to examine the bottle without worrying about the liquid that's inside...but work with me here.

Normal ICE operation: Suck, Squeeze, Bang, Blow. Repeat as necessary. All of the combustion activity creates heat, carbon, soot, planet killing gasses, and (unless you're a Prius driver) a nice smile on your face from acceleration.
OK...so take away the Bang. Instead of dealing with zillions of explosions, and white hot gasses, you use the engine's compression and nice cool outside air (Suck, Squeeze, Blow) and the drive train to slow the vehicle....but how is this any worse on the vehicle than burning gas??? Isn't it actually a little bit better than running fuel through the motor since you don't have the physical, thermal, and chemical stresses of combustion to deal with?
As far as the OP's real question....I'd say no. There's been no engine "damage" other than that which is theoretically caused by running the motor more than it need to have been run during the first 24,000 miles of its service life. To be sure you've wasted a bunch of energy but I'd ask your boyfriend why it's so much more beneficial for an engine to be turning and burning fuel than it is for it to just be turning. While you're on the subject you can begin to explore his relationship with your driving if you decide to upgrade to co-habitation, marriage, etc.
You are exactly right in that it's "generally" better for you to use brakes for braking, especially in a Prius with its regenerative braking, but I wouldn't spend any more time worrying about any damage done to the car. Do what the manual says (now is a good time to read it again) and there is no reason that you shouldn't get hundreds of thousands of miles out of this car AND get great mileage while you're doing it.

God Luck!

 

There is one other reason to be careful in "B". On slippery surfaces it can be slightly more hazardous than using the brakes as only the -front- wheels are slowing the car. I haven't noticed any effect from this, but I suppose it -could- cause whatever. Maybe in a high speed corner.

 

Regen also only uses the front wheels.