Comparing the Prius v. Honda hybrid idle-stop feature

You are correct. The "ev-only" for the new civic hybrid happens only when you are already in motion. It cannot move the car from a stopped position w/o the gasser.

This is why the Prius has scalability to a plug-in: larger electric motor, better/more powerful battery pack.

The PSD (power-split device) is the true wonder of the Prius engineering and allows it to be such a great rolling marvel. Not-so-humble opinion!

 

That is a reasonable simplification of the way it works most of the time.

I don't know much about the Honda, but some exceptions on the Prius are:

If the gas engine and catalytic converter are sufficiently warmed up, the car will cut fuel to the gas engine as soon as you take your foot off the accelerator (rather than when it comes to a stop). With the Prius' ability to coast, this can happen quite a while before the car comes to a stop. Then as the vehicle slows down, once it drops below 41 MPH, the gas engine will stop spinning as you continue to slow the car with your foot off the accelerator.

When the battery charge gets low, the Prius will start the gas engine every time you lift your foot from the brake to inch forward. If you are using significant electrical power (A/C, headlights, radio, etc.) and the battery power drops far enough, the gas engine will start up to charge the battery a bit even while you are not moving.

When you pull away from the customs booth, the car may get all the way to 40 MPH before the gas engine starts up, or it could happen before you even reach 5 MPH. It depends on a variety of factors, but most especially how far you press the accelerator pedal (how hard you accelerate), and how much charge the battery still has left.

If you sit in the traffic you describe for long enough, the gas engine or catalytic converter may cool off enough that the car will start up the gas engine every time you inch forward for the purpose of heating these components back up to their operating temperatures.

Note that almost all the electricity in the battery comes from burning gasoline. Therefore while you may not be using gasoline directly to inch forward, you will be using electricity that was created previously by burning gasoline, and gasoline will need to be burned again later to charge the battery back up again. Even so, at such slow speeds, I believe it is quite a bit more efficient to use the electricity and recharge from the gas engine than it is to try and move the car with the gas engine directly. As I understand it, the gas engine just can't move the car very efficiently at exceptionally low speeds.

 

That's the way my Civic-driving son explained the different between my car & his - he can't start up without the engine running & I can.

 

Another difference is the transmission. The Civic uses a conventional CVT, where the Prius has a transmission unlike anything else; the HSD. The HSD has one set of planetary gears, no belts (there is a drive chain, but this is not part of the transmission), no shifting, no clutch (other than a fixed one to avoid shock loading), and it is always in gear. It makes the hybrid system on the Civic look like a Conestoga wagon.

Tom