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So, "c"'s MPG is more affected by cold?

Discussion in 'Prius c Fuel Economy' started by cyclopathic, Feb 3, 2015.

  1. cyclopathic

    cyclopathic Senior Member

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    No stat data, and it is apples to oranges comparison at this point as C is still going through break in.

    BUT with the same 50% blocked lower radiator vent it looks like it takes a few miles more to reach to operating temps. As a result avg MPG is down.

    This is probably due to smaller engine, and lack of plastic shielding under engine bay.

    What is your observation? How much grill do you block?
     
  2. skayaks

    skayaks Active Member

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    Depending on my route, speed, and ambient temp I may block with anywhere from 1 to 4 long strips of pipe insulation. I never block the last (lowest) of the grille opening slots.
    BUT, I believe it's vital to have a means of monitoring coolant temp before doing any grille blocking.
    Coolant temp will change dramatically when the heater is off (set to "Lo") or set to warm the cabin.
     
  3. cyclopathic

    cyclopathic Senior Member

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    I usually keep heater off until engine heats up (which co-insides with getting out on open highway, and then put it on Auto/A/C off/re-circulation

    I've looked at your Fuelly log and it looks your fist winter was much worse than this one. Did you block it back then? or was it due to break-in? thnx
     
  4. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    The C seems to work just like the GenII Prius. Different than the GenIII hatchback, that's just from personal experience.
    The C seems
     
  5. skayaks

    skayaks Active Member

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    "I've looked at your Fuelly log and it looks your first winter was much worse than this one. Did you block it back then? or was it due to break-in?"

    I can't find how to view more than 30 fill-ups on Fuelly (anyone know how?) but I was grille blocking before 2/2/14.
    I'd guess the relatively poor winter mileage last year was due to (1) Break-in, (2) more 400 mile highway trips to VT and back.
     
  6. ftl

    ftl Explicator

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    At the bottom of the Log Book section there are Next and Previous buttons that let you view all the entries one screen at a time. And there's [View All Fuel-ups] which shows all entries on one screen but in an expanded format.
    Edit: There's also an option to export all data to a CSV file, which can then be imported into a spreadsheet or database on your PC. This is at the bottom of the Log Book section, disguised as a little blue disk icon: [​IMG]
     
    #6 ftl, Feb 4, 2015
    Last edited: Feb 4, 2015
    skayaks likes this.
  7. cyclopathic

    cyclopathic Senior Member

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    Thanks!

    It was a bit of let down when the MPG was ~42 for first 100mi. For comparison our Gen3 is getting 56-60 in same conditions.
    It is up to 50+ with 600mi, and 53 on last tank (still going). Part of it break-in, part of it different tires (Energy Savers vs Fuel Savers), still..

    With respect to previous stats it is under Log Book -> Next, as FTL said.
     
  8. cyclopathic

    cyclopathic Senior Member

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    Could you please elaborate?

    BTW admire your DeLorean avatar; back to the future!
     
  9. skayaks

    skayaks Active Member

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    "At the bottom of the Log Book section there are Next and Previous buttons..."

    Thanks, don't know how I missed that. I started grille blocking on 12/21/13, so a bit later in the season than this year.
     
  10. GregP507

    GregP507 Senior Member

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    There's no benefit to blocking the grill unless your coolant thermostat is failing to keep the engine up to operating temperature. For cars with electric fans, leave a gap between the blocking material and the radiator, so the fan can pull air through the rad if it requires it. There may be some aerodynamic benefit from closing-off the grill-openings, but I doubt it would be measurable.
     
  11. cyclopathic

    cyclopathic Senior Member

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    From what I found if there is any aero benefit, it is very minor. The biggest factor is shortened warm up cycle, and longer shut off intervals at highway speeds. You'll see the difference in MPG if warm up can be shortened from 5mi to 3 on 15mi route.

    I wish Toyota or aftermarket would offer the active shutter gill Prii, like GM does for Cruze Eco.
     
  12. mahout

    mahout Active Member

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    cold engines will get less mpg simply because the cold air and engine need more fuel. blocking off the radiator will help the engine warm up but the longer it takes the less mpg. true of all IC engines. cold air only helps at max power requirements because air is denser and for same reason when cold air is charged to combustion chamber more fuel is needed to burn properly.
     
  13. mahout

    mahout Active Member

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    actually there is. at really cold temps the radiator will cool the coolant so much thateven virtually closed thermostat will not let engine reach design operating temperature. and you don't have to live in AK for thsat. I've seen it in MI.
     
  14. cyclopathic

    cyclopathic Senior Member

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    Yesterday's morning commute was cold 16F, and total MPG was 48.6. On the was back it warmed up to 36F, and MPG jumped to 57.4 same route. I do not recall Gen3 being affected so much.

    Update: had low 60s yesterday. On 30mi trip MPG jumped to 63.2. This is on warmed up engine.
     
    #14 cyclopathic, Feb 7, 2015
    Last edited: Feb 9, 2015
  15. cyclopathic

    cyclopathic Senior Member

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    there is no doubt that cold engines get worse MPG, and why th I happens. Question is if "C" is more sensitive then Gen3 due to smaller engine, better ventilation and other design changes. For example Gen3 is using exhaust to heat coolant, and "C" don't?
     
  16. xraydoug

    xraydoug Active Member

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    My c is very sensitive to cold. My commute is only 2.4 miles. I have all the grill blocked that seems to help a little on this short trip. On longer trips of over 10 miles my mpg will climb up close to 70. But most trips are short so average is only 52 this year so far.
     
  17. GregP507

    GregP507 Senior Member

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    Very little MPG is lost through the grill, except in very cold conditions. You are losing it mainly through the increased viscosity of the lubricants.
     
  18. cyclopathic

    cyclopathic Senior Member

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    He means blocking shortens engine warm up time which is a main MPG killer on short trips.
     
  19. GregP507

    GregP507 Senior Member

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    It fails to do that, except in very cold weather.
     
  20. Hodr

    Hodr Junior Member

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    On my second winter with this car and I drive about 90% the same tank to tank.

    In the winter I consistently drop 10mpg on the same route to work. It seems to come in steps; if the temperature is below freezing (as it is much of winter here) I lose 10mpg. If its between 32(f) and about 50(f) I lost around 5mpg. Anything over 60(f) and I can usually get better than 60mpg.

    My route is exactly 5.4 miles, and I have never blocked my grill (though I should, I am afraid I would forget to remove it for long trips).