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Toyota Prius MPG-Real World Numbers

767 messages,  Last post on Sep 28, 2009 at 9:21 AM

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What is this discussion about? Toyota Prius, Hybrid Cars, Fuel Efficiency (MPG), Sedan


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#641 of 767
Re: Calculated vs Car figures [cdhc] by jana6
Oct 30, 2008 (4:41 pm)
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Replying to: cdhc (Oct 24, 2008 5:11 pm)

I read through the Adobe article as well as your info again and thank you. I do have a question. Why is it better to glide than to coast when coasting charges the battery? Isn't charging the battery better in the long run? Shouldn't the Energy Monitor battery showing green vs blue best?
#642 of 767
Re: Calculated vs Car figures [kdhspyder] by prius2007
Oct 31, 2008 (5:32 am)
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Replying to: kdhspyder (Oct 29, 2008 9:36 am)

re: "A couple of other important suggestions:
  
2. DON'T STOP - EVER!!!! This may seem ridiculous ...When you come to a stop light or stop sign normally you will stop the vehicle. It takes a huge amount of energy to get the vehicle rolling again.
  
You will likely get your best fuel economy on a 30-60 min trip where you never have to stop and you must keep to driving at about 35 mph due to traffic or to road laws."
 
Thanks for the great advice spyder! "Don't stop - ever" ... "normally you would stop...". You must have a lot of followers, based on my observation of driving behaviour.
 
Can you please help me with my mileage? I'm struggling
 
So far have driven 26,999 miles since Apr 2007 and pumped 455.46 US gallons of fuel. No matter how hard I try I can't average " And the result will be be about 47-48 mpg". I can't even get that on a single tank let alone overall. Can you help me out please?
 
I do stop when I have to (stop signs/light ...) and I do take frequent longer trips than the 30-60 minutes you stated as best for MPG. I admit driving on the HWY (50% of my driving is HWY) and do go up to and over 60 MPH. Are these the reasons why I can't get your predicted 47-48 MPG?
 
Thanks in advance for all your help
Gabe
#643 of 767
Re: Calculated vs Car figures [jana6] by cdhc
Oct 31, 2008 (6:56 pm)
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Replying to: jana6 (Oct 30, 2008 4:41 pm)

I don't ever glide. I always coast in order to charge the battery. I want that battery charging every possible moment. I'm finding that more & more I'm able to keep the battery indicator in the upper light green that I used to. Yes, the green is more fully charged than the blue. The stronger your battery is charged, the easier it is at takeoff for you to start rolling solely on electrical power.
#644 of 767
Re: Calculated vs Car figures [cdhc] by jana6
Oct 31, 2008 (7:08 pm)
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Replying to: cdhc (Oct 31, 2008 6:56 pm)

That's what I do too. That's why I couldn't understand why it says gliding is better but they were talking about gas mileage. Could we possibly get better gas mileage when there is no friction on the engine as there is when coasting? At least that's how I'm interpreting what they are talking about. I would assume it's a trade off that possibly results in better gas mileage but less battery charge. Curious... Any ideas?
#645 of 767
Re: Calculated vs Car figures [cdhc] by prius2007
Nov 01, 2008 (1:49 am)
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Replying to: cdhc (Oct 31, 2008 6:56 pm)

Hi cdhc,
 
Your advice is good in fact I do the same, but if you listen to the experts / people with more experience with the Prius they will tell you this:
There is an energy conversion loss (gas to electric or electric to kinetic). Guess well all the stored battery energy comes from - yes your gas engine. Initially it had to come from the battery and any replenisment has to come from the battery. They recommend to stay off the battery and that a no arrows glide is better than running off the battery. Like you, I also coast (blue arrows only going to the battery) when approaching a red light / stop sign. I've been doing more gliding (no arrows) as a result whenver possible, but since I don't want to hold up traffic I do also run on the battery often.
 
Good luck sounds like you're doing well
Gabe
#646 of 767
Re: Calculated vs Car figures [jana6] by prius2007
Nov 01, 2008 (1:53 am)
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Replying to: jana6 (Oct 31, 2008 7:08 pm)

Hi jana6,
 
You hit the nail right on the head - the claim is that there is no friction when gliding. BTW the Prius MFD is great in showing instant MPG but it only goes to 99.9. I recently bought a Scangauge which goes up to 9999 MPG and even better if you switch it to L/100KM a zero reading means there is not even a trickle of gas is being used when gliding.
 
Best of luck , sounds like you got the bulk of the concept and you can put it into practice,
Gabe
#647 of 767
Re: Calculated vs Car figures [prius2007] by kdhspyder
Nov 01, 2008 (5:32 am)
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Replying to: prius2007 (Oct 31, 2008 5:32 am)

Nice job! 27000 mi / 455 gal = 59 mpg.
 
You obviously got the secret Super Ultra Efficiency option package that very few knew about and which allows you to be in the upper 1% of all Prius owners. I didn't know the code for that option or I would have chosen it also.
 
For the rest of us plebians we have to make do with just good normal results. Nice hand, sir.
#648 of 767
Re: Calculated vs Car figures [jana6] by cdhc
Nov 01, 2008 (7:30 am)
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Replying to: jana6 (Oct 31, 2008 7:08 pm)

I do have a background on the subject of regenerative braking, kinetic energy, etc. For a living I engineer & sell industrial machinery, and regen braking is nothing new. Its just new to the consumer market. The primary source of energy in the Prius is, yes, the gas tank. One thing about the engineering that went into designing the Prius is that it utilizes every opportunity to capitalize on motion being used to charge the battery. On a car that has conventional brakes, during the action of braking, heat is generated. This heat is a direct representation of energy that is lost. In regen braking, the energy is captured from the momentum of the wheels, and this energy is used to back-drive the electric motor, thus charging the battery. Its important to brake lightly. If you use a heavy brake, the brake pads kick in to stop the car, and energy can be lost due to heat being generated.
 
When you are driving, and you take your foot off the accelerator (coasting), the car then uses the momentum of the wheels to back-drive the electric motor, thus charging the battery. This method of charging is much more efficient than regen braking since there will not be as much energy lost due to heat being generated.
 
Its true that gliding can help you go a little further than coasting, but gliding does nothing at all to charge the battery. What may be perceived as friction while coasting is actually the electric motor being back-driven. And yes, with any rotating part, there is friction. That's just something that cannot be avoided. You even have friction in the wheel bearings while simply gliding.
 
I don't know. There's people that get better gas mileage than me, but I'm happy with my average of 57.5.
#649 of 767
Re: Calculated vs Car figures [prius2007] by cdhc
Nov 01, 2008 (7:31 am)
Reply

Replying to: prius2007 (Nov 01, 2008 1:49 am)

I do have a background on the subject of regenerative braking, kinetic energy, etc. For a living I engineer & sell industrial machinery, and regen braking is nothing new. Its just new to the consumer market. The primary source of energy in the Prius is, yes, the gas tank. One thing about the engineering that went into designing the Prius is that it utilizes every opportunity to capitalize on motion being used to charge the battery. On a car that has conventional brakes, during the action of braking, heat is generated. This heat is a direct representation of energy that is lost. In regen braking, the energy is captured from the momentum of the wheels, and this energy is used to back-drive the electric motor, thus charging the battery. Its important to brake lightly. If you use a heavy brake, the brake pads kick in to stop the car, and energy can be lost due to heat being generated.
 
When you are driving, and you take your foot off the accelerator (coasting), the car then uses the momentum of the wheels to back-drive the electric motor, thus charging the battery. This method of charging is much more efficient than regen braking since there will not be as much energy lost due to heat being generated.
 
Its true that gliding can help you go a little further than coasting, but gliding does nothing at all to charge the battery. What may be perceived as friction while coasting is actually the electric motor being back-driven. And yes, with any rotating part, there is friction. That's just something that cannot be avoided. You even have friction in the wheel bearings while simply gliding.
 
I don't know. There's people that get better gas mileage than me, but I'm happy with my average of 57.5.
#650 of 767
Re: Calculated vs Car figures [cdhc] by jana6
Nov 01, 2008 (5:38 pm)
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Replying to: cdhc (Nov 01, 2008 7:30 am)

This does make sense. Thanks. (And I have no engineering background so thank you for putting it in terms I understand!) I do wish I could get 57.5 mpg but I guess it just isn't in the cards for me. My 15-20 minute drive to work is 1/2 city, 1/2 highway. If I would get up early enough to leave early, I could go all city and do better there but.... Also, even though I plan my short trips in clumps, it just isn't that easy to avoid the 5 minute drives from here to there. But at least I now understand why I'm not getting the mileage and am willing to accept it. I do appreciate all of you for all your help.-

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