I have a 2007 Prius and have a question about the fuel consumption screen. How do you get the little green cars? What do they mean? and why are they important. I took the car out on the first highway road trip and could sometimes getting 2 cars in 5 minutes and than would go 20 mintues before I could get another one or even a half of one. Any information would be great!!! Still trying to get better than 50 MPG.

 

They are leaves in the shape of cars. As the screen tells you, they represent power you make by degenerative braking or reducing the throttle like with coasting down hill. This is the power that is put into the Hybrid battery.

 

Each green car shown on the consumption screen five-minute bars represents recovered energy equivalent to a fifty watt bulb illuminating for one hour.

Half symbols are also shown but I do not know if that means fifty watts for thirty minutes or twenty-five watts for one hour.

Look in your owner's manual in the 'fuel consumption section' for additional information.

Four symbols is the maximum during five minutes. I have seen all four several times, usually when coasting down a long mountain pass.

 

Same amount of energy either way (90kJ).

 

As a general rule, you want to drive so you avoid "regenerative" energy. The usual techniques:

1) allow car to slow down well before coming to a stop
2) crest a hill at the lowest safe speed.
3) try to run 5 mph or so slower when you can

Bob Wilson

 

I'd guess this is the same as what those down under call "avoiding the turtle" - but why?

 

As a general rule, there will be some loss of energy, even with regeneration:

• Mechanical to MG2 transfer - 98%
• MG2 to electrical and inverter losses - 95%
• Battery charge losses - 80-95% (depends on current)
• Battery discharge losses - 95%
• Electrical to MG2 energy conversion - 95%
• MG2 to wheels - 98%

There are significant facts not covered in this simplistic analysis with the major effect being how much power is being captured and released. But the end-to-end efficiency is the product of the individual efficiencies:
.98*.95*.95*.95*.95*.98 ~= 78% (best case)

Now if you can drive in such away that you always 'roll to a stop' or 'roll up a hill' and descend the other side, you're in gravy.

Bob Wilson

 

The obstacle is the path, then. Interesting to try in the Sierras and coastal mountains, this "rolling up a hill".

 

With the Prius, the trick is to keep the ICE in efficient speed ranges. If you are passing trucks on the upgrade, slow down and follow them up at their speed. On the backside, you can pretty well go at any speed as long as you don't hear a lot of engine noise (or sirens.)

Bob Wilson