What powers the car at a stop light ?

Can you be more specific with your question. Not sure how to answer it. By idling, you mean 'gas engine running, right'?

 

I'm no expert but when I stop at a light my ICU shuts down. At that point i assume the hybrid battery is powering the car.

 

You might want to check this out...

http://priuschat.com/forums/gen-iii...max-mpg-driving-techniques-youtube-video.html

 

Gypsy tears.

 

When the car is cold (as in first switched on) then the engine will run for a while to warm itself and the catalyst. Once it is up to temperature then the engine will switch off when not required, so when approaching a stop sign the engine will cut off as soon as you take your foot off the gas, when you start to brake the car starts to charge the High Voltage battery and when you stop the HV battery will be powering the a/c with the engine off. When you put your foot on the gas to set off again, depending how fast you wish to go depends on how far the car goes on electric drive before the engine kicks in.

That's the basics - there's a little more to it such as after coming down steep hills etc, but as far as driving it it should be no different to a traditional car - just let the car do its thing.

Oh and the big difference and benefit of the Prius over the Honda Insight, is that the Prius powers the a/c when the engine is off (and can do for about 20 minutes or more depending) which is good news when stuck in a jam.

 

EPA mileage in the city is higher mostly because of lower speed driving. Aerodynamic drag goes up by the square of speed, so highway driving sacrifices a lot of energy to the gods of aerodynamics.

Note that EPA city driving is not sitting still at a traffic light. If your car isn't moving, your mileage is zero. Waiting for a light is not good for mileage.

The EPA city cycle includes some stop and go, but it also has a fair amount of low to medium speed driving. If get into an urban parking lot type of stop and go, your mileage will be worse than the EPA figures.

Tom

 

As I understand it:
Normally at a stop light, electric power is keeping the accessories running.
Two exceptions:
When the gas engine is still warming up (see grumpy cabbie's post above).
When your accessories have drained too much energy from the battery, and you have to use gas to keep it from completely discharging and being damaged (as when you are in a traffic jam on a hot day and using A/C).

Gang, do I have this right? Or is it more complicated than this?

 

http://priuschat.com/forums/other-c...uth-about-epa-city-highway-mpg-estimates.html discusses what goes into the EPA tests.

 

It is more complicated. But the gist is correct.
The Prius extraordinary mileage is a result of a number of factors listed in order of importance as I understand it, including:
1. The engine is tuned for maximum efficiency. It would be undrivable if not for the electric part of the hybrid system. This gives it about 10% to 20% improvement over "normal" car engines.
2. The engine shuts down when not needed.
3. The system recovers some energy that would normally be lost to heat in the brakes with regeneration.
4. The HSD is very low drag and the car is very aerodynamically efficient so it coasts well.
5. The HSD allowed Toyota to remove some "parasitic drag" components from the system, such as belts driving generators, water pumps and A/C system pumps.

BTW, after more than -10 years- on the market, other manufacturers are -still- trying to improve their ancient designs to match the Prius. They have so far failed miserably. Though their advertisements claim otherwise.

Hence my description "extraordinary mileage".