When I take my foot off the brake the car immediately engages the electric motor and the car starts to creep forward. Why? Because that is what happens in an ICE only car so they built it into the Prius? To arrest my fear that I may not be in the correct gear? Is there some mechanical or electrical reason it has to do this? Curious minds want to know. I was sure this would have been discussed before but I wasn't successful at a search.
I believe the consensus is that it occurs because thats what you expect to happen. People in general are use to "inching up" when waiting at a traffic light by just taking a little pressure off the brake - without any input from the motor, you wouldn't creep. So does it have to happen? no. is there any electrical or mechanical reason for it? no. there's just a psychological reason for it, and Toyota wanted to make sure the car was as "normal" as possible for people to operate.
There's actually a safety rationale for it, albeit somewhat obscure. Go through http://techno-fandom.org/~hobbit/cars/prius-linkfarm.html and look for "NPRM". Yes, it bugs a lot of people, and dropping into Neutral as you arrive at your stop mitigates it. . _H*
the "CREEP" simulates the same effect of a 'standard' automatic transmission. All you have to do to prevent it: Press the brake pedal firmly. You can observe and test this by putting the MFD on the "Energy" screen and watching the "arrows." You can see that when you press the brake pedal very lightly, energy will flow to the wheels, but press it more firmly and the "arrows" will disappear and no energy flow will be shown. ENJOY your remarkable PRIUS.
And as an auxiliary function, there's a hill-hold feature. It will try to stop you rolling in the opposite direction to your gear selection by increasing the torque more, up to some limit. (Some say this is just the creep function, but they're wrong. It would be rather miraculous if the creep force exactly happened to balance out the hill slope - it's actually sensing motion and adding extra force to hold you stationary.) Thanks for the link, Hobbit - interesting. Unless I'm misreading though, it's only requiring creep in reverse, not forwards. But it makes sense that the Prius does it symmetrically.
<div class='quotetop'>QUOTE(hobbit @ Nov 17 2006, 11:55 AM) [snapback]350781[/snapback]</div> But keep in mind that the battery will not charge in Neutral. You're better off to push the Park button. Tom
<div class='quotetop'>QUOTE(qbee42 @ Nov 17 2006, 12:03 PM) [snapback]350845[/snapback]</div> You're better off to just keep your foot on the brake like any other automatic transmission car.
I suspect the primary reason is that Toyota wanted customers to feel that they were driving a regular car, especially during the test drive. I'm more used to manual transmissions that automatic transmissions with the slushbox - torque converter that causes the creep. Still the creep doesn't bother me like the simulated engine braking when we take our foot off of the accelerator pedal. Yes it's nice that the drag is regenerative braking more than engine braking, but I'd rather that the car would simply glide when I took my foot off the brake, with no battery flow to or from the motors. This might seem strange during a test drive. Could Toyota make this a user selectable option? Can anyone find a hack to enable this? (I can dream can't I?) If this was enabled during test drives it might be a strong selling point for some buyers. Sensing the car glide effortlessly with it's great aerodynamics, lrr tires, and low friction drivetrain might help them feel the efficiency of the car?
<div class='quotetop'>QUOTE(theorist @ Nov 18 2006, 09:00 PM) [snapback]351593[/snapback]</div> Given that the car's behavior is "programmed" it would be nice if Toyota would give us some choice. I would like to be able to select maximum economy, maximum performance, or normal; with the balance between ICE and electric being reprogrammed in each case. Maximum economy would coast when your foot is off the gas.
