Startup sequence, batteries and ICE

When you first start the prius, the small AUX battery turns on the computers to switch to the main (hybrid) battery, which then everything is run from.

Then, for about 10 seconds, the ICE stays off you and you accelerate forward or reverse, and then the ICE will kick in to warm up and reduce emissions.

If its warm outside, it wont stay on very long, and you can stay on electric power alone for a good mile, and then the ICE will come back on for a moment to charge the battery and keep itself warm.

42mph is the maximum speed the electric motor can keep the car moving, otherwise the RPM's of the electric motor would be going to fast.

Everytime you let go of the accelerator as long as the ICE is warm, then it shuts itself off to conserve fuel. When you brake, you regenerate electricity to recharge the battery

 

See
http://www.toyota.com/prius/
http://john1701a.com/

Prius always operates itself so as to minimize pollution. Batteries and ICE are used as needed. The ICE will always run for at least a little while, enough to warm itself up. In the real world it gets roughly 40 MPG on cold days and short trips, and much better on warm days or long trips, but unless you drive a lot or the price of gas goes up a lot gas savings will not pay for the price difference between it and a Corolla.

 

The Prius is not really designed to operate on electric power alone for more than short spurts. It is designed primarily to use gas and electric simultaneously. On a warm engine, if you accelerate very gently, you can go a ways on electric power before the engine starts. But if the engine is cold, or you accelerate normally, the engine will start almost immediately. At steady city speeds, on level roads, if the battery SOC is high enough, the engine will sometimes stop and the car will go a ways on electric.

The Prius is not an electric car with a gas engine. The Prius is a hybrid gas-electric car which achieves maximum efficiency by using both together. Under most normal conditions, the engine is running, and the battery is alternately being charged and discharged, with occasional brief periods of electric-only operation.

I get 50 mpg at 55 to 60 mph. MPG drops rapidly at higher speeds. I get around 44mpg at 75 mph in warm weather. Less when it's cold.

While you won't pay for the difference between a Prius and a Corolla on gas savings alone, the Prius is much more value than a Corolla. You might as well compare a BMW to a VW as a Prius to a Corolla. Even a Camry cannot compare to a Prius in terms of features and quality.

At highway speeds the engine is running, and the battery is alternately assisting and being recharged. On the power-flow diagram you will see the arrows to and from the battery alternating rather rapidly.

The Prius is probably twice as efficient as a similar-sized conventional car. It achieves this through a variety of means, including having a smaller engine (which is possible because of the battery assist when added power is needed) and the revolutionary power-split-device, which allows the engine to always operate much closer to its optimum rpm than a conventional car can.

Hope this helps

 

What Daniel said.

As far as your thought the gas engine is possibly marginally efficient at highway speeds: It is a small engine, designed slightly different (Atkinson cycle) from a 'regular' gas engine. It is efficient and coupling it with the electric motor gives it the extra it needs, only when it needs it.

Most of the horsepower in 'regular' cars is not needed most of the time. Since they have no other way to get 'extra' when they need it, they have to have the excess capacity.

Engage the Cruise Control on the highway and unless you are watching the screen that shows energy flow, you will never know when the electric kicks on and off. If you do look at the screen, you'll see it showing everything from gas engine only, gas and electric, or only charging the battery on a down hill. It all adds up to around 50 MPG.

 

There's a saying among Prius owners: "Just Drive It!"

You'll be surprised at how often the energy-flow changes, all automatically. In fact, if is wasn't for the Multi-Display, you likely wouldn't have any idea how dynamic the system is.

You get the clean emissions and great MPG without having to be considered about what the car is doing. Details are available if you want them, but they certainly aren't necessary.

 

One more point. I've said this before, as have others, but it bears repeating:

If you need economical transportation, the Prius is not for you. A 5-year-old Civic or Corolla will cost you far less per mile over the life of the car, simply because the first owner absorbed the depreciation. Even a new Civic or Corolla will probably cost less per mile over the life of the car, depending on what gas prices do.

You wouldn't buy a Jag or a BMW to save money. You buy them for the luxury and features they offer. The Prius offers features not available on any other car, as well as some only offered on much more expensive cars. It's a super-cool, clean, green people-moving machine. If you can afford it, it's a fantastic car. Maybe, if you really want it, and the cost is a bit of a squeeze, the fact that it burns half as much gas may tip the scales. But the gas savings will be a small factor.

This car, in my opinion, would be worth the cost even if got mundane mileage. Build, features, quality, all make the Prius worth it's sticker price. The super-ultra-low emissions and phenomical mileage are just a great big bowl of gravy.

 

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What you're thinking of is the ICE, which can be motionless up to 42 MPH. Above that speed, the ICE must rotate to keep the generator (MG1) from over reving. On a downhill grade at highway speeds, it is common to be coasting (regenerating), gliding (no power to the wheels, either electric or ICE), or be in full electric mode.