Electric motor whine

The good news is that the "Electic cars are dangerous since they're so quiet" crowd should be happy to hear this. The bad news is that the only annoying-to-me sound that the Prius makes is when the gas engine starts, and I can hear (and feel) IT!

Give me the EV whine over the ICE rumble any day.

 

Mine is louder than that. My take on the braking, which has been discussed to the hilt before, is that the generator is engaged only partially on coasting, and fully when braking, or maybe even progressive change. It seems that they designed coasting to be about like a normal car to avoid any consumer misunderstanding or some other reason.

I think the friction brakes apply just like a normal car as soon as pedal is touched, but the extra full regen makes it much less work for them. I wish they would have had full regen on coasting as well, or a switch to change it back and forth.

 

<div class='quotetop'>QUOTE(Mr.Vanvandenburg @ May 28 2007, 08:53 AM) [snapback]450978[/snapback]</div>

Friction braking starts at about 9 MPH normally. They will activate on panic stops. Regen increases with pedal pressure.

 

Before I disagree, I want to say I view these forums as places for discussion, and disagreement should be viewed as impersonal. If I am wrong, fine, if right also fine, it isn't important to me who is right or wrong, just to learn.

The brakes work like normal brakes, all the time, I'm pretty certain. I am pretty sure this would be a safety requirement in any case. One of my reasons to believe this is in the manual where it states don't rest your foot on the brake to prevent premature wear. So even the slightest pressure works the brakes, according to the factory. Even just from driving I can tell this. At a stop it is necessary to press the brakes to avoid creeping, and before the system is even started the brakes must be applied. They do apply at these times. It seems the pedal is connected to the pads and shoes by the electric booster and hydraulic system, similar to any car except they use a vacuum booster. In light braking I can often hear the pads scraping the rotors. I am open to learn more, maybe this is all wrong, but don't think so.

Using "B" would only waste energy, as why use the ICE air compression as a brake, when what is desired is for the generator to do that as much as possible? I thought B was mainly for descending steep hills, since there is no "lo" or "2" gear, or ICE engagement otherwise.

 

<div class='quotetop'>QUOTE(Mr.Vanvandenburg @ May 28 2007, 12:22 PM) [snapback]451071[/snapback]</div>

I am afraid that you are wrong. Take a look at this Autoshop 101 - Automotive Training and Resource Site For Automotive Electronics webpage.

 

I think mine sounds just a bit like a jet engine, when I'm gliding downhill... I like it

 

The Prius brakes are different from any other car. In other cars I am always careful to not keep the brakes depressed for more than a second or two when going down a steep hill, in order to not heat up the brakes too much. In the Prius, I can keep the brakes lightly depressed all the way down the hill, and charge the battery that way. The pads aren't being used, only the regen system, so it's perfectly safe. The pads only come in to play if I slam on the brakes, which I try not to do unless in a panic stop situation, which has happened to me once recently on the freeway, where I had to slow from 55mph down to 35mph in an instant because of traffic in front of me. Fortunately there was no car in the next lane, where I went to avoid hitting the car in front of me.

Dave

 

It does not say when the brakes are pressed the hydraulics are not activated. It says there is regen braking when the accelerator pedal is released, and additional hydraulic braking when the brake is depressed. Brake pedal pressed=hydraulic action to whatever degree. Similar, but different due to generator resistance, to any other car. It is totally false that friction brakes only are used below nine mph, that is very tough to believe, that one. I think they are always used to some degree but less than a normal car.

As to "B' I refer to p.146 of the owner's manual. It (Toyota, not me) states "B" is for additional ENGINE braking, and may reduce economy, (it states, not me.) Rotating the engine is just like driving an air compressor, a waste of energy. Sounds logical to me.

This site is Toyota?

 

<div class='quotetop'>QUOTE(Mr.Vanvandenburg @ May 28 2007, 03:03 PM) [snapback]451131[/snapback]</div>

Sorry, you are still wrong.

 

if you download the NCF manual from the Toyota site and read up on the braking system in the Prius you will see that the design uses what is called a stroke simulator and the purpose of it is to allow for a small amount of brake pedal depression without applying pressure to the hydraulic part of the brake system and allows for a rheostat that is connected via the CAN to tell the computer to use regeneration via the MG's to slow the car. When you press thru the stroke simulator you activate the hydraulic portion of the brake system. This is quit easily viewed if you have CAN-view or another device that will read the brake pressure along with the regen current.

 

Yes this device is described in the training manual link someone posted p.5-10. Just what is the amount of stroke during zero hydraulic pressure? So far I have only seen agreement to what I first said, there is braking through both sources when stopping, according to need from each. They call it cooperative braking in the manual posted above. A normal car also has a small pedal dead spot or "play" from rest. It would have to be this way to avoid pads constantly touching rotors. MG2 doesn't have pads so can start working immediately fom zero.

It is very hard to believe the friction brakes only work at 9 mph and below, which is what is being said, and I believe I was questioning in the first place. The MG2 only works on the front axle, (someone must agree with that) so when hitting the brakes, at say 60 mph, there would only be front wheel braking. That would be the pits. The EBD would also have no function until below 9mph as the back brakes are dead till then, according to these beliefs. That is a waste of EBD technology and not likely. It makes no sense whatsoever to me. I have had enough arguing about it.

This site needs to upgrade it's server.

 

the total travel of the stroke simulator is about 20% of the brake padal travel. Once thru it your into hydraulic braking. Till then you can get about 55 Amps of regen which is about 45% of the total available with further brake pedal travel. If you don't exced the limit of the stroke simulator you don't have any hydraulic pressure and if you don't need more braking than that amout of regen produces you won't have the pads on the rotors till 9 miles an hour. You can actually feel the brake take over just by using light pressure and watching the speedo and when you go thru 9 you'll feel the hydraulic brakes take over.

 

If you regen for the first 20% of the brake pedal why would you need engine braking when you are going down a steep decline?

You would not be using friction brakes to keep your speed down and would be taking advantage of regen braking going down the decline.