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Disappointing hwy MPG

Discussion in 'Prius c Fuel Economy' started by cyclopathic, Nov 17, 2015.

  1. mertechperformance

    mertechperformance Active Member

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    In my c I normally drive at 72, sometimes cruise, sometimes not. Average 51 to 54 depending on terrain and conditions. If I slow to say 68 or slower I've managed to average over 58mpg. My worst freeway trips have been at 75-80mpg when late or going up to tahoe. Averaging as low as 38mpg.

     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Any time you drop your highway speed you will improve your mpg, dramatically. I like to abide by the limits, for numerous reasons. And if limits are set high and I'm not impeding anyone, I'll drop down 10 or so.
     
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  3. cyclopathic

    cyclopathic Senior Member

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    So I hooked TorquePro and looked what is going on.

    at 73-75MPH RPM fluctuate in 2,200-2,600 range
    at 62-63MPH RPMs are in 1,100-1,900 range.

    Looks like Toyota cut costs by simplifying Prius C intake valvetrain, and it is not optimized for higher RPMs.

    So increased aerodrag is getting ICE out of optimum range and causing sharp MPG drop. I suppose aeromods and better LRR tires are needed
     
  4. mertechperformance

    mertechperformance Active Member

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    Not so much that they cut cost. It's the prius c, CITY. It's really meant to be the prius for large city dwellers in Japan. not too much high speed there. It's a barely upgraded/changed priusII drivetrain. Between old tech, less aerodynamic styling and being a cheap car of course they aren't going to dump in a ton of money it's basically a niche parts bin car... which is now enjoying mass market appeal and sales numbers.



    EVERY toyota for the past 15 years or so is vvti. Some very few are vvtli which IS like vtec... this is NOT a vvtli aka variable valve timing with lift intelligence. Vvti can be just intake (most motors) or intake and exhaust aka dual vvti as seen in new corolla, tundra, etc etc etc. Vvti does not have a different set of lobes just an adjustable cam gear. Vvtli has hydraulically activated system to switch to different lobes.

     
  5. cyclopathic

    cyclopathic Senior Member

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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Or just do an end run around the whole situation, choose routes where you can slow down.
     
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  7. mertechperformance

    mertechperformance Active Member

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    Yeah he wants best handling prius c but wants lowest lrr tires and won't lower car. I don't think he's much too willing to drive less sporting. Not hating, just observing.



    But yes aeromods will help mpg as will hard as hell craptastic lrr tires. But handling will suffer for the worse with both of those.

     
  8. cyclopathic

    cyclopathic Senior Member

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    I have a set of Conti TrueContacts in 195/60 waiting, they can't be worse than OEM FuelMax, no?And not only that but also w/o throwing a bunch of money at it.No compromise.

    I normally do, but sometimes when you face 600mi drive you have no choice. I could just drive 5mph under as every Prius we passed did, but what's the fun?
     
  9. mertechperformance

    mertechperformance Active Member

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    I drive 7 over 90% of the time and get 48 to 54mpg. So I do not know. And 600mi. Phew that's nothing. I've done multiple 7 to 800 mile days



    Maybe my rear touring spoiler and mid hatch spoiler help me out at speed, ha ha

     
  10. cyclopathic

    cyclopathic Senior Member

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    I feel your pain, when I got older can't motivate myself to do it anymore.

    I've done several 800-1100mi days on motorbike and while it is physically harder it is actually easier to stay focused than in the car. The longest day in the car was from Key West to Wash DC, ~1,200mi. Nowdays anything which would eat into my sleep time count me out.

    That 600mi drive (568mi actually) was after spending the whole day driving/hiking in Smoky Mountains, Deal's Gap, Blue Ridge, Cherohala skyway, so add roughly another 200mi in the mountains prior.
     
  11. mertechperformance

    mertechperformance Active Member

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    I posted 7 over. Ha ha.



    My longest on 4 wheels was 1400 have done it twice. Longest 2 wheel is about 500. Wrists kill. But yes much more awake.

     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Wow, talk about "one man's ceiling...". My main issue is running the car often enough to keep the battery happy.
     
  13. mertechperformance

    mertechperformance Active Member

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    Work sucks, I put sooooo many miles on my ride for them...

     
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  14. cyclopathic

    cyclopathic Senior Member

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    You are the man, 1400mi non-stop is too much.

    Yes on bike wrists could be big, esp if you ride twin and have handlebar buzz (all of them do). But with gel grips, proper adjustments and built up stamina it is doable, though nowdays my throttle pinky goes numb pretty quick. Worse thing is when you have to do it day after day, on our x-country trip by the time I got my bike to California I could barely hold on to handlebars. Getting passed by Toyota pickup truck on PCH was classic, though he had Bilsteins on it, so it wasn't too bad, and my bike was overloaded and pillion would try to stand up bike if I leaned it any much.
     
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  15. mertechperformance

    mertechperformance Active Member

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    Not the man just stupid and twas younger. I routinely get stuck with 700 mile days and gets old. Life is life.

     
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  16. GasperG

    GasperG Senior Member

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    Why not add BSFC in the Torque app, formula is on PriusChat somwehre ;) Or you can do it yourself with custom PIDs (engine torque, engine rpm, fuel flow)
     
  17. cyclopathic

    cyclopathic Senior Member

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    My issue is that MAF readings on Torque are way off. It reads 458CFM, which is ridiculous number for 1.5L with 5,000 redline. The reading is x4 times off.
     
  18. GasperG

    GasperG Senior Member

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    I think there are more ways to measure fuel flow, there is also option "Enhanced MPG calculation" that may help.

    I had custom PID for BSFC and it was bouncing (data delay) around 250-220 g/kWh, almost regardless of rpm.
     
  19. mrpinkie

    mrpinkie Junior Member

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    My 46 mile commute is all highway with a 70 mph speed limit. I only have about 3000 mile on my 2015 C4 so far but I notice a 4 mpg increase after the 3rd tank of gas. I currently get 47ish mpg at 70 mph for my commute. I have tried setting cruise to 67 mph just to see if there was any increase in economy, and it has been less than 2 mpg.

    But when I put my family in the car to head to a friends house for Thanksgiving dinner, I set the cruise to 75 mph and holy crap does that make a difference. I only added 1 adult and a 30 lbs toddler. For a 36 mile drive I got 34 mpg. On the way home I set the cruise to 70 mph and it came up to 42 mpg.

    I realize that this car was designed to be efficient in optimal conditions, and I traded in a V8 Tundra Double cab. As for the efficiency, I notice everything will affect the mpg. Coming from a truck, I was already used to running the speed limit, now I am conscious about getting to my cruising speed. I have owned the car for a little over a month, and have saved $$$$$ that would have been spent on gas. $80+ a week down to $20+ a week is pretty nice. At first I was concerned that I wasn't getting in the 50 mpg range, but I am more aware of how hilly my commute is. I have to agree that it really isn't a highway vehicle, but it is reducing my costs and I have grown to enjoy driving the "little one"
     
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  20. cyclopathic

    cyclopathic Senior Member

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    when you take it for 5k service tell them to check alignment. Mine was off by a country mile. Fixing that made +3mpg improvement. Also it takes some time for break in, so you will see better MPG after first oil change. And the other thing C MPG is temperature sensitive, so while it was in low 60s a couple months back it is -5-7mpg worse now good luck!

    EDIT: when you say hilly and in NC, around Asheville?
     
    #60 cyclopathic, Nov 30, 2015
    Last edited: Nov 30, 2015