Whirring noise when coasting downhill.

Nope - what you hear is the engine working as brake by compressing air (and burning no fuel in the process), essentially offering resistance rotating --> braking the car.
This happens in D when the battery is almost full, regardless of whether you press the brake pedal or not.
Only when accelerating, of course, will the engine stop doing that.
In B, the engine will always add braking force in this fashion, regardless of battery charge, to increase braking force. B should be used exactly when going downhill.

 

Do you have the gear in D or B?

Some "whine" is normal whenever the car's motor is acting as a generator, ie: anytime you're coasting, decelerating.

 

I have a steep hill I go down and the engine practically screams when I have cruise control set. Battery doesn't need to be fully charged. I've found that if I tap the brake pedal lightly, it quits doing it. I have no idea what it is. If I put it in B mode, I still get the loud scream. A light tap of the brake makes it go away. Anyone have this? I haven't been too concerned but perhaps I should?

 

I went down my first mountain range yesterday, it did the same thing, but I just ignored it, figuring it knew what it as doing.

 

I don't like going down hills in my Prius. Now I try to avoid them, if possible.

Even short-distance hills of 1/4 mile to 3/4 mile. (Speed limit 25). I have to ride the brakes all the way down, or else the car picks up too much speed. Does the "B" mode not work on those shorter distances, and lower speeds?

I never hear the "engine braking" kick in. I would welcome the engine screaming if it will slow down the car, and allow me to get off the brakes.

 

You can get the same sound - exit a motorway (or anywhere for that matter) and wind your DRCC speed down from 100 to 60km/hr - it certainly slows quickly - and gives that "sound".

I generally slow with the brake pedal trying to gain regeneration, but if I'm lazy, I'll do it that way.

 

congrats and welcome! any hill? small, medium, or large? mine doesn't make any noise on small or medium, and i've never gone down a large hill.

 

... and I always thought, what goes up Must come down!

 

I have a few hills around here. The shortest is about a mile long and is quite steep. A drop of three hundred feet or so? There are others that are longer and much greater changes of elevation. I'm in the Sierra foothills near Yosemite. On these steep hills I get this noise. It is noticeably loud and horribly obnoxious. Manual braking makes it shut up.

 

You should be ok with short hills: the charge/discharge system will not be overwhelmed. I'd have no qualms about just using the brakes, it's primarily regen that's happening.

It's only coming down mountains, long downhill stretches, that you need to use B; when the battery will get charged to capacity, and you still have a long ways to the bottom. That's when there's a danger of the conventional brakes being used to the point of overheating.

 

Call me nuts, but I think B works better when I have the drive mode in Eco.

I went down those hills again this morning, and I felt a significant difference this time.

Man, you talk about confusing!

 

friday, saturday, sunday, monday...

 

As we say in the 'hood, "it is what it is."

 

it's all good, under the hood.

 

Yeah, this happens on those big long hills. My battery is filled up. I'll give the B a go.

 

If the B doesn't slow you down while in power mode, switch to eco and try again with B.

If this car gets any more confusing, I'm trading it in for a Yugo!