Stuff you can do to improve your winter mileage

Discussion in 'Knowledge Base Articles Discussion' started by efusco, Nov 22, 2008.

  1. efusco

    efusco Moderator Emeritus
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    1) Check your tire pressure...often. I run mine higher than most people, but lower than some. A safe and fairly comfortable target would be 44psi in the Front and 42psi in the rear. This will reduce your rolling resistance...I can feel when my tire pressure drops even 4 or 5 psi b/c of decreased glide distance.

    2) Wear a coat, gloves, and maybe a hat (see #3 below)

    3) Leave your heat set as follows:
    a) Max Cool
    b) A/C OFF
    c) Auto OFF
    d) Fan at lowest setting
    *This is the same as the 'vent' setting you'd use in warmer weather.
    Trust me here, in all but the coldest weather, esp. if you park in a garage, it takes a while for the temp to get that cold, and even if you have the heat on it takes a while to warm up. If you turn on the heat at all the electric heaters in the circuit come on and force the ICE to run more, drain for the electric heaters cause a hit, and the air circulating around the ICE keeps it cool longer making warm up take longer.
    You can turn on the heat once you're warmed up.

    4)Install an Engine Block Heater
    Inarguably the single best thing you can do. Your ICE temp starts b/w 110F and 130F and takes far far less time to hit 157F (fully warmed up). That means you get to turn on the heat sooner. Obviously it can be hard to tell what your ICE temp is unless you have a Scan Gauge or some other means to monitor. But if you know what Stage IV is and you can get into Stage IV then you're fully warmed up.

    5) Install Grill blocks
    Using foam pipe insulation jammed into the grill slats, upper and lower, will reduce air flowing around the ICE. This is safe to do any time temps are below 50F outside...you can even do the upper at warmer temps than that. This really has a dramatic effect by keeping the ICE warmer while gliding/stealthing and allows for much faster warm up times...

    6) Avoid Defrost
    Pretty self explanatory, the defrosters put the fans on max, engage the AC, and cause a huge power drain while on. Clearly think safety first and use it as necessary, but leaving it on until the windows are crystal clear all around will take a huge hit to your FE. Following #1 above will often help you avoid the need for defrost. Scrape your windshield before starting the car to get rid of snow and ice. Use an anti-fog on the inside of the windshield to avoid minor fogging and reduce the need to use the defrosters.

    *I'll add links and pics later if I remember to.
    **Apparently great minds think alike. MSantos produced a brilliant article 3 days before I posted this one that also puts this one to shame...seriously. It's posted over at Cleanmpg.com and though I'm not one to advertise other sites, if one is seriously interested in all the things you can do to prepare for winter his is the article to go to...
    http://www.cleanmpg.com/forums/showthread.php?t=17560
     
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  2. john1701a

    john1701a Prius Guru

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    If you have an aftermarket device, like ScanGauge, watch for 145°F.

    When the coolant temperature drops below that, the engine will start back up. Until then, you can take advantage of the Max Hot setting with the blower on a low speed.

    It's nice knowing exactly how much heat is still available when sitting there waiting for the stoplight to change.

    .
     
  3. Stefx

    Stefx Member

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  4. Norm611

    Norm611 Junior Member

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    The warehouseautoparts site indicates that the 100W heater should be used for oilpans with a capacity of 2-5 quarts. (the Prius takes 3.5 to 3.9 quarts). The 250W heater is recommended for oilpans in the 8-20 qt range.

    Norm
     
  5. Stefx

    Stefx Member

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    Good point, I didn't verify that.
     
  6. PaulHS

    PaulHS Member

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    This is one of those half-thought-out ideas so bear with me.

    Has anyone considered mounting an electric ceramic heater between the grille and the radiator, connected to the same timer as the EBH? With grille-blocking, it should provide some general pre-warming to the coolant in the radiator as well as the engine compartment.

    We've had a cold snap here in PA (morning temps around 26 degrees F) and I was disturbed to find my scangauge reading a low 85 degrees (normally closer to 120 degrees until now) when the ICE first powered up.

    Any thoughts one way or the other?
     
  7. efusco

    efusco Moderator Emeritus
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    It would certainly help warm the engine compartment. I think the issue becomes how much energy are you going to use to save how much gas (aka energy)? IOW, will the ICE be that much warmer using another 600W+ energy.

    What I have considered, but not yet had the guts to try to fabricate, is a small low wattage heater to put in the intake vent for the battery. Warming the battery, esp. keeping it above about 40F, seems to have distinct advantages in efficiency in really cold weather.
     
  8. PaulHS

    PaulHS Member

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    Although I don't make a lot of 30+ minute trips, I've noticed that when I do, there seems to be a slight boost in efficiency beyond the 30 minute mark. Without any empirical evidence, I've attributed that to the entire HSD reaching thermal equilibrium, as opposed to only certain components achieving a minimum level of efficiency. (This would be during mild to cool ambient temperatures.) So the theory is that warming the other components of the system would help simulate that 30 minute mark. ??? It may be well worth the energy cost.

    Interesting. Any idea how much benefit you might expect? How would you power your heater?

    You have indirectly pointed out something I have misunderstood. It is very noticeable that in the winter months, the battery charges into the green much faster. I've been assuming that to indicate the same charge capacity as in warmer months. I see now that I was wrong. Obviously the battery holds less total charge when cold, just like most other batteries.
     
  9. ken1784

    ken1784 SuperMID designer

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    Hello from Japan,
    This is the first introduction on PriusChat forum which Japanese Prius drivers used since 2006.

    Do you think we could improve our winter mileage to keep the engine coolant temperature higher than normal?
    Do you think it is better to keep the engine room temperature higher than normal?
    Have you ever felt the Prius engine is easy to be cooled down because of the engine-off coasting?

    If you answered yes on one of these questions, you'll be a good candidate for the following modification. :)

    The standard coolant thermostat opens at 82C(180F) and we see the nominal 88C(190F) coolant temperature after complete warming up.
    There is a higher temperature thermostat which opens at 88C(190F) on the market and the nominal coolant temperature can be seen 6C(10F) higher than normal.
    CAR-FLAP Thermostat WV56TA-88? - Yahoo! shopping
    (Please note this internet shop is for Japanese customer only.)

    edit: note that the gasket also needs to be replaced at same time.

    Please refer to the attached chart for the coolant temperature graph.
    The sky blue line is for the normal thermostat at 17C(63F) ambient temperature and the other lines are 88C thermostat used.

    We see a few percent mileage improvement, but no ill effects can be seen even in hot summer for these two years.
    Please install it at your own risk.

    Enjoy your winter driving.
    [email protected]
     

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  10. ph43drus

    ph43drus Junior Member

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    Thank you for this interesting idea and the supporting graph Ken!

    For English speakers: I can't read Japanese, but I know a few characters. I believe the various lines on the graph are labeled something like:

    Dark blue: Outside air temperature 4-6 centigrade, cloudy weather with snow
    Green: Outside air temperature 10-13 centigrade, clear sky
    Purple: Outside air temperature 6-7 centigrade, rain
    Turquise: Outside air temperature 17 centigrade, clear sky, standard "samo"

    "Samo" is written phonetically in way used for foreign words; I'm guessing there's no Japanese word for "thermostat", and this is more-or-less the sound of the English word (or the first two syllables, anyway).

    The x-axis is labeled something like "time interval axis". I don't think the units have been specified. Y-axis is labeled water temperature.
     
  11. Stefx

    Stefx Member

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    The idea is interesting.

    Supply might be an issue.
     
  12. ken1784

    ken1784 SuperMID designer

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    Your translation is perfect!
    Yes, "samo" means "thermostat".
    The x-axis unit is "0.1 second", and the graph is based on his 50 minues commuting.
    The graph tells us he needs 1,200 seconds(20 minutes) to reach the complete warming-up temperature.
    Please note that he used the EBH and he never truned on the A/C or heater.
    He reported he won't see above 80C(176F) for his entire commuting if he turned on the heater(A/C).

    [email protected]
     
  13. ken1784

    ken1784 SuperMID designer

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    Hope sigmaauto.com or japanparts.com will help you to supply the thermostat and the gasket.

    [email protected]
     
  14. biff44

    biff44 New Member

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    Once again, what is the point? If you are installing electric block preheaters, if you pay 50 cents to heat the block up with electricity from your home, or if you do not have a preheater and have to pay 50 cents of gasoline to heat up the engine the same way--what is the rational for the extra personal effort and installation cost? You are not making ANY engineering sense here!
     
  15. efusco

    efusco Moderator Emeritus
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    3 hours at 400W/hour is WAY less than $0.50 most of us pay around $0.12/kW, so it's maybe a quarter at most.

    And it's not all about money...it's about saving gas, reducing fossile fuel use and emissions. Now, that said, a lot of us do get our electricity from coal..and that's not clean I absolutely grant you. But the reduction in gas use is an end and a goal in itself and that's a big part of "the point".

    IN addition, the fact that you can warm up and have heat without a hit to your FE much more quickly is a nice creature comfort benefit as well...if you need something more practical to use for an excuse.
     
  16. Stefx

    Stefx Member

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    Ironically, you are not making any engineering sense.

    The engine's temperature will depend on the quantity of energy used to heat it (wether it's Joules, kWh, etc). The ratio between cost and energy is quite different between electricity and fuel.

    This chart will give you an idea of various forms of fuel and energy density
    Image:Energy Density.PNG - Wikipedia, the free encyclopedia
    Gasoline technically contains around 34.2 MJ/L. Over here one liter costs 0.80CAD (0.64 USD). If around 25-35% is converted into mechanical energy, most of the rest is heat, but a lot of the heat is exhausted. I lack the data to calculate how much of the heat ends up heating the engine block... if you figure that part out, you can start making thermodynamics engineering sense.

    Dollars are irrelevant in the thermodynamics equations, they are solely used in economic analysis. I have books full of thermodynamic equations, and none of them have an equation with dollars in it.

    34.2 MJ is about equal to 9.5 kWh by the way. I recall seeing that most EV cars get about 3-5 miles per kWh.

    Now on top of the thermodynamic and economic analysis, there is (as mentioned in the preceding posts) an overall objective to minize fossil fuel consumption.

    There is also the comfort factor. In cold winters, an electrically pre-heated engine block will start heating the passenger cabin earlier than an engine that wasn't pre-heated.

    A warmer engine will also enable the more fuel-efficient hybrid modes of the Prius, where the engine shuts down when idling or coasting for example.
     
  17. ken1784

    ken1784 SuperMID designer

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  18. efusco

    efusco Moderator Emeritus
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    Here's an informative graph showing how the cold affects battery performance. Thus, keeping the battery warm (via garaging?) improves it's performance/efficiency and can improve your FE.
    [​IMG]
     
  19. patsparks

    patsparks An Aussie perspective

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    Warm engines wear less so last longer.
    A great way to improve you winter mileage and your quality of life is to move to a warmer climate.
     
  20. Artist

    Artist New Member

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    On the other hand, car batteries that get too cold, won't start. At 27 below (before wind chill) where I grew up in Illinois, the only cars moving that winter morning were those with garages. It was a very cold walk to work.

    Why stress out all those batteries!!!:fear:I plan to buy a battery warmer and mud flaps for the Pruis we just bought yesterday. I don't want my batteries to have a long, stress free future.

    the Artist
     
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