Top Speed on the Electric Motor?

Losses through the generator, inverter, battery, inverter and motor are much greater than through a few gears.

Post 18 gives a brief overview of why HSD works.

A very good Otto-cycle engine is about 20% efficient while the engine in a Prius is up to 40% efficient.

 

This is good to know, I've been letting the car do that every chance that it gets.

 

I should point out avoiding regen by driving up to red lights and stop signs on throttle then braking hard, or braking in neutral wont work, coasting to a stop or almost to a stop or avoiding stopping by timing traffic and traffic lights will help a lot.

 

Correct,

Purely in terms of fuel efficiency, Friction braking is bad, Regenerative braking is better, No braking is best.

Also, since most of the fuel is used to overcome friction and drag, the slower you drive the less fuel you use. There is a lower limit to this, but I think it is lower than 20 MPH.

 

In more cases than many people realize, yes.

This is true, and the car's computers do a pretty decent job of deciding which to use automattically for any given condition. People (hypermilers), who make extra efforts to learn what is best and when, can learn to outthink the car because they know what the terrain and driving environment ahead looks like and the car doesn't.

Keep in mind that the car will operate in a less fuel efficent manner when it needs to for emmissions purposes and driver/passenger comfort. In particular, it will burn fuel to heat the catalytic convertor, to maintain operating temperature of the gasoline engine, and to supply the people in the car with heat as requested via the climate controls.

Most of the fuel efficiency of the Prius is due to the use of the small atkinson cycle internal combustion engine (ICE). This engine uses fuel very efficiently and provides enough power for cruising a most legal speeds. However, the average car buyer would be so unsatisfied with the acceleration of the car, that few would be willing to buy it. A typical Otto cycle 1.5L DOHC ICE like in the Yaris provides about 106 hp. That's 39.5% more power than the highly efficient Atkinson cycle 1.5L DOHC ICE in the Prius which provides only 76 hp. 39.5% more power in a car that weighs 606 lbs (20%) less than the Prius. The Prius makes up for this shortcomming by adding in powerful electric motors (295 ft lbs torque, 67 hp) to fill in when the acceleration needs of the driver exceed the power available from the ICE.

While it is inefficent to generate motive power just to turn around and convert it to electricity, and then convert that into chemical storage, which will later be converted again to electricity so that it can be converted back to motive power. . . . There are times when this is more efficient than running the ICE at RPMs that would otherwise be required to propel the car. Also, storing the energy that would otherwise be tossed away by the friction brakes is always more efficent. Storing even 0.1% of the energy lost to braking is better than losing 100% of it, and the Prius certainly does better than that. So when possible the car works to make sure there is enough power in the battery for likely extra power needs later.

So the ICE is where most of the efficiency comes from, the electric motors make the car sellable, and once you've got those pieces, it isn't very difficult to pick up a bit more fuel savings by shutting the ICE off when the car isn't moving.

 

Peak fuel economy comes at 41 mpg in the Prius.

A common pulse and glide speed range is 30-40 mph, though if there is any sort of traffic, this type of driving is not typically feasible.

 

Master Wayne Brown wrote 20 mph is most efficient.
http://priuschat.com/forums/fuel-economy/14675-most-efficient-speed-best-mpg-4.html#post385271

Ken@Japan

 

Thanks Danny, that is just what I was trying to say but you did it so much better.

 

Hmm, that's different from the other charts I've seen... I'll have to dig one up.

Edit: Here's the one I was thinking of. So 41 mph isn't the most efficient, but it's pretty flat between 20-40 mph, certainly not a huge peak like on the previous image.

 

It's nice to see all this being talked about again. It's what the Prius is all about and understanding this stuff is the foundation for getting outstanding gas mileage, and attaining the original EPA estimates of 60MPG.

Since those EPA numbers have been lowered, it seems everyone 's expectations have been lowered, people are missing what this car is really capapble of, and maybe don't know how to get it.

Lowering the EPA numbers for the Prius was like the public schools lowering achedemic standards and adjusting test score curves, so the kids not willing to put forth the effort can pass too. Thus they never attain what they're capable of. SAD.

 

That's the old one from the same author, Wayne.
He revised it for more realistic one.
Please read the thread again...
http://priuschat.com/forums/fuel-economy/14675-most-efficient-speed-best-mpg-3.html#post186848

Ken@Japan

 

Does anyone know the power of MG1 and then MG2? Im guessing the 67hp is both of the motors power combined? Just wondering

Its been said MG1 cant run past 10K now. That means we can get to about 65mph running power to MG2 just electric before MG1 gets to 10K. I take it MG1 is making power spinning backwards at 9,000rpm?