Engine idle changeover (ICE to ELECTRIC)

<div class='quotetop'>QUOTE(smokey1 @ Mar 4 2007, 12:13 AM) [snapback]399801[/snapback]</div>

Yeah, that's your ICE turning off. When the car is at a stop or moving very slowly it's more noticeably rough. I wish I could go around in stealth mode all the time. =)

 

It almost like a small, almost imperceptible shudder.... indeed it is the enging shutting off. If you think thats bad, and in order to properly appreciate how truly smooth it is, just think about how much noise and vibration your regular ICE vehicle made when starting and turning off. The Prius does that many, many times during each trip, mostly imperciptable.

So in reality, that little shudder is not much at all. You'll get used to it, and as the Dr. says, its a little more prounounced in the winter than summer.

Welcome to PriusChat!! :lol: :lol:

 

I think that has to do with the atkinsonized intake valve timing. To increase efficiency the Prius actually blows some of the intake charge back into the manifold before the valves close for compression. That way the compression stroke is shorter than the power stroke. But since this is going on, there will always be some fuel vapor left in the intake that needs to be burned before the engine cuts off. That means you might get a couple of cycles during shutdown where the engine is burning off that fuel, and those cycles aren't going to be terribly smooth. It may be worse in the winter if fuel gets a chance to condense and collect outside of the combustion chamber.

 

<div class='quotetop'>QUOTE(smokey1 @ Mar 4 2007, 01:13 AM) [snapback]399801[/snapback]</div>

My two week old '07 Prius does exactly the same thing. I was wondering about it just as you were. I'm glad to see that's "normal".