Prius Generations in cold weather

Discussion in 'Gen 3 Prius Main Forum' started by teraja, Dec 12, 2012.

  1. walter Lee

    walter Lee Hypermiling Padawan

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    Yes. In the 1980's there weren't many cars with computer controlled fuel injection which compensated for the cold temperatures :coffee: - Before 2000, most cars had temperature senstive springs controlled valve carberators and a distributor-rotor which sometime had trouble starting in the freezing temperature. I remember putting in gasoline anti-freeze additives in the gas tank to help my naturally aspirating 1974 Vega work in the winter. Today's computerize car sensors have made startups more reliable in the cold - you might say it's made us all a bit spoiled. :p :)

    You can buy a specially made air take cover (aka a grill billet) for the 2nd and 3rd gen Prius - it's pretty expensive (>$100 last I saw) . The commercial air intake covers are mesh like screens that fit over the air intakes. I like most Prius owners use pipe foam insulation to grill block my Prius air intake grills that can be purchased inexpensively at the home improvement stores.

    Some people like Cleanmpg.com 's Hobbit have already experimented with insulating the engine compartment of the Prius - albeit I don't have a link for you. Very smart guy that Hobbit is. The bad news is that you would have to buy the insulation in a roll and custom cut and mount it yourself. Much work it is. I'm not sure where you can get the insulation material in the EU but in the USA can be purchased from internet stores like www.jcwhitney.com
     
  2. john1701a

    john1701a Prius Guru

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    I haven't seen any criteria to warrant that. The system is remarkably adept at maintaining a consistent operating temperature while the engine (once warmed) is running.
     
  3. kbeck

    kbeck Active Member

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    Haven't noticed the stability sensors come on unless the wheels have actually started skidding. What I have noticed is that it's blame difficult to skid the car in funny directions. Took it out shortly after buying it into the aftermath of a 6" snowstorm, then spent some time trying to get the car to do funny angles in a deserted parking lot. I could make it travel in a turn with the steering wheel all the way one way or the other, skidding like crazy, but definitely under control; letting go the steering wheel put the car back in a straight position right away. Flipping the car end for end appeared to be impossible, although I imagine drastic maneuvers on glare ice might do the trick. Snowy conditions on the Garden State Parkway (the scourge of NJ) would result in perhaps a little skidding, but the car would go in the direction pointed. No complaints.

    As far as gas mileage: During the temperate portions of the year, the car would warm up in the first half mile and would be showing 55 mpg about 1.5 miles from the house and around 65 mpg 13 miles further on, just before the major hill where I work, about a 40-45 minute trip. With the temperatures cold, 50 F and below, it takes about 2-3 miles before that 50 mpg number is hit and I have around 45-55 mpg at the base of that hill, depending upon traffic. So, the cold weather affects mileage, pretty much as described around here. It's not clear if straight-line 65 mpg mileage is affected, but I get the feeling that it is, but I haven't really dug into it. If I was feeling ambitious, I'd reset the odometer every mile or so and take lots of numbers, but I'd rather drive and avoid accidents than do that!

    KBeck
     
  4. walter Lee

    walter Lee Hypermiling Padawan

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    On of my first experiments with grill blocking was to drivie on I-270 Northbound in Maryland going at 50 to 65 mph when the driving temperture is about 65 F degrees with both top and bottom grill blocking on. After 45 minutes, the ScangaugeII xgauge fwT increased to 200 F and appeared to be climbing so i stopped over at a reststop and pulled off the grill blocking and the coolant temperature dropped back down to 188 to 196 F - which is safe. Having a 2010 Toyota Prius' gasoline engine coolant temperature go over 205 Fahrenheit degrees for any sustained time period is not advisable. For a short periods of high speed driving - Grill blocking is safe, but the standard mantra at Cleanmpg.com ( which I am a member of as well) is to monitoring the coolant temperature if grill blocking when the outside driving temperature is above 50-60F and during extended periods of high speed driving. This advice might appear overly cautious - but the primary motive is to make absolute sure to put the safety of the driver and the vehicle first regardless - an expert or elite hypermiler can sometime bend or break the rules to get higher fuel efficiency - but for the rest of us - these rules keep us out of harm's way.
     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Originally posted January 2010, I've edited my post to reorder the test cases and added standard units:

    Blocking the fender, air inlet reduces the amount of drag creating air that goes into the engine compartment. This drag effect becomes more severe with high-density, cold air. So I wanted to test the original configuration and two blocking approaches: recessed and conformal with the front bumper.

    The recessed block leaves a 'parachute' that spills air out the edges. This air carries away energy, increases drag. However this is consistent with ordinary, air inlet blocking. The conformal block avoids the air spillage out the corners and provides what should be the minimum, drag.

    TEST A - 51.6 MPG @70 mph (4.56 L/100 km @112 km/hr)
    [​IMG]

    TEST B - 53.3 MPG @70 mph (4.41 L/100 km @112 km/hr)
    [​IMG]

    TEST C - 53.6 MPG @70 mph (4.39 L/100 km @112 km/hr)
    [​IMG]

    Protocol and test conditions
    • 57F (14C), dry pavement, humid, altitude ~650 ft (~200 m)
    • two runs, West and East, south wind at ~10 mph (16 km/hr)
    • I-565 Jordan Lane Huntsville AL to Mooresville AL
    • cruise control maintained speed, GPS calibrated
    • does not include acceleration to speed or deceleration at turn arounds
    • +13 miles (20.8 km) each leg, added together for total performance
    • 2010 Prius (VZW30), 8,500 miles ODO, OEM tires, 45 psi (310 kPa)
    • ICE and transmission oil changed at 5,000 miles
    • Shell 87, E10
    • Warmed up at least 20 minutes before first run
    • Disposable, cardboard shields held with duct tape
    Test notes:
    1. The test temperatures were close to a 'standard day' so it should be fairly easy to calculate the effects of air-temperature on vehicle drag and performance.
    2. Although I have both ScanGauge II and AutoEnginuity, I used the engine fans to determine if it was getting too hot. The engine radiator fans did not come on during these tests.
    3. To estimate the temperature effects on mileage, divide it by the percentage air density change. For example, unblocked air inlet 51.6 MPG @59F (15C) and 70 mph (112 km/h) should be 51.6/97% ~=53.2 MPG @77F (25C). The partial block MPG improvement, 51.6 MPG to 53.3 MPG is roughly equal to raising the effective temperature ~18F (~10C.)
    Column 1
    0 [th]C[th]F[th]% drag[tr][td]35[td]95[td]94%[tr][td]30[td]86[td]95%[tr][td]25[td]77[td]97%[tr][td]20[td]68[td]98%[tr][td]15[td]59[td]100%[tr][td]10[td]50[td]102%[tr][td]5[td]41[td]104%[tr][td]0[td]32[td]106%[tr][td]-5[td]23[td]107%[tr][td]-10[td]14[td]109%[tr][td]-15[td]5[td]112%[tr][td]-20[td]-4[td]114%[tr][td]-25[td]-13[td]116%
    Source: Density of air - Wikipedia, the free encyclopedia

    Bob Wilson
     
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  6. john1701a

    john1701a Prius Guru

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    I don't endorse blocking entirely or when outside temperatures are anywhere near that warm, so my experiences are quite different. At the most extreme, the highest temperature I've ever seen is 198*F.

    The purpose is for rapid warm-up and heat retention when there's snow on the ground.
     
  7. retired4999

    retired4999 Prius driver since 2005

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    I agree I only block the bottom 1/2, and only when temps are under 40 degrees, which is probably the next few months. I have never had a problem.
     
  8. jsfabb

    jsfabb Active Member

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    You can easily block the bottom half when temps are in the 50s. I have been doing it here in Long Island since late September and check my UltraGauge frequently. It has definitely been in the 70s a few days since then and I haven't had any problems. I just started blocking my upper grill and have only seen a high temp of 197.6*.

    I have gotten over 60mpg on my way home from work (35 miles) with temps in the mid 40s.
     
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  9. jayman

    jayman Senior Member

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    Welcome and congratulations on your car.

    The Prius does not use a conventional immersion-style coolant heater. There is a machined recess in the aluminum engine block. The 400 watt electric heater is a rod about 10 cm long. It ships with a package of thermal paste that is smeared on the heater before it is installed into the engine block. The heater warms the coolant indirectly by conduction, by warming the block.

    This is not unique to the Prius. Every Toyota now uses this system. My 2007 FJ Cruiser has a 4 litre aluminum V6 that uses the same style heater. You will dramatically improve warmup time, and reduce cold start engine wear, by using the heater. DEFA supplies the correct heater for Scandinavian countries.

    I too used studded tyres on my Prius, as I found studless winter tires did not provide good ice traction which left my Prius helpless in winter. I ran Goodyear Nordic, which was sold in your country as the Goodyear UltraGrip 500.

    For my FJ Cruiser I run factory studded Nokian Hakkapeliitta Sport Utility 5. My Significant Other purchased a 2012 Chevy Impala and for her car I put on factory studded Nokian Hakkapeliitta 7. In my humble opinion Nokian makes the best winter tyres on planet Earth.

    Some will claim studded tyres destroy roads and cause lung cancer. The Swedish road transport authority VTI has conducted extensive testing which resulted in mandated changes in how studded tyres are made for Scandinavian countries. The stud has a special rubber shock absorber that all but eliminates road wear.

    The claim that studded tyres cause road dust isn't true. Leaving sand on dry roads results in PM10 inhalation, so once the roads are dry the sand should be vacuumed up.
     
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