dandeman
Premium,MVM
join:2001-12-05
Chapel Hill, NC
 ·AT&T Southeast
| reply to iLive4Apple
Re: Hybrids
Own a 2006 Prius Hybrid... The average MPG on a recent 7500 mile cross country trip was 51.7mpg..
Average would have been even better if trip had not included long periods of driving 75-80mph on I-90 and other western interstates where speed limit is 75mph. It was averaging around 44mpg at those speeds.. Other places saw mpg as high as 64mpg at times..
Very comfortable cross country car! |
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justin
Australian
join:1999-05-28
Brooklyn, NY
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| I'm curious, what is the engineering reason why highway mpg is lower than around town mpg for the prius?
it seems to me it should be vice versa. Around town you are accelerating the car and decelerating it which even if you recapture the momentum with regenerative braking has to be very power hungry due to efficiency losses. On the highway you only need to overcome rolling resistance and wind resistance.
Is there something about the design that is more efficient at 20mph stop start than 70mph constant?
Oh wait, I know why.. because drag goes up exponentially with speed, right? so to propel something with drag at steady 70mph vs steady 35mph, although you complete the journey twice as quickly, you need three (or definitely more than twice) as much pushing power?
So if you could drive your prius at 45mph on the highway, you'd see over 50mpg? |
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lotusracer
Premium
join:1999-11-26
Moline, IL
| said by justin  :I'm curious, what is the engineering reason why highway mpg is lower than around town mpg for the prius? it seems to me it should be vice versa. Is there something about the design that is more efficient at 20mph stop start than 70mph constant? Oh wait, I know why.. because drag goes up exponentially with speed, right? So if you could drive your prius at 45mph on the highway, you'd see over 50mpg? Drag may have a little to do with it... but mostly it has to do with the fact that around town, you are more likely to get more benefits from the electric part of the drivetrain. You can get some pure electric "stealth" driving in town, where on the highway, you tend to use gas only or gas/electric combined.
Years ago on the Yahoo Prius list, at least with the 'classic' 2001-2003 Prius it was determined that MPG begins to drop off at around 62mph. If I remember correctly, several owners said that the best figures were around constant 45mph.
Something interesting I've seen myself is that driving highways on level ground can sometimes bring you lower economy figures than when you are driving on slightly hilly terrain. Odd when you consider that the constantly variable transmission can really rev the engine up when you go up a hill!
Several things can affect a person's hybrid economy experience... short trips will lower your average.... cold weather will lower your average. But then, those same things will lower economy figures in any car. |
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