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Advice for short trips in the heat

Discussion in 'Gen 3 Prius Fuel Economy' started by austingreen, Aug 18, 2010.

  1. austingreen

    austingreen Senior Member

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    The air conditioning and heat has caused a big drop in mpg on my short trips, which weren't great before. I have a bad combination of factors. 65 mph highway just a little bit after start up. Hills. Temps in the high 90s when I leave work. Low state of charge often starting up caused by the ac running.

    I'm not going to run without ac in this heat. My tires are aftermarket 17s inflated to 42/40 (max 51). Should I let the car cycle through, perhaps without me in it at start up, to let the engine warm up before accelerating? Should I brake more aggressively or do something else to have the soc higher? Thanks for your advice. Trips to the lake also have poor fuel economy, but its 14 miles of winding hills, 35-65mph, and I don't think anything really will help that.
     
    #1 austingreen, Aug 18, 2010
  2. drees

    drees Senior Member

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    You want to minimize the amount of time the AC runs, so here's what to do:

    Leave all the windows down for a few minutes with the AC off until the inside of the car reaches ambient.

    Then roll the windows up and crank up the AC.

    Don't let the car warm up - with 100F temps, it's already pretty warm. Get up to cruising speeds swiftly - don't dawdle around.

    Don't brake harder - you waste energy that way. Smooth is always better.

    At a minimum get a windshield shade and the windows tinted with a good quality IR reflecting tint.
     
    #2 drees, Aug 18, 2010
  3. austingreen

    austingreen Senior Member

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    Thanks.
    I already have tinted windows, and open a couple of windows to blow out the hot air at the start of a drive. I don't have a windshield shade.
     
    #3 austingreen, Aug 18, 2010
  4. GSW

    GSW PRIUS POWER

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    You might check the vent switch when the A/C is on. On startup my "Auto" mode switches to recirculation and stays there. Once the A/C temp is comfortable, I reach over and switch off of recirculation which has got to help reduce compressor usage and maybe save a bit of mpg.
     
    #4 GSW, Aug 19, 2010
  5. tumbleweed

    tumbleweed Senior Member

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    I guess that requires some explanation for me. If you switch off recirculate the system brings in outside air, so If the outside temperature is warmer than the climate control temperature setting it seems that it would require more compressor usage. In the fresh air mode, vice recirculate, it appears you would be cooling hot outside air instead of cooling inside air that is already been through the system and is cool?

    When using A/C I have always left mine in recirculate unless it's cooler outside.
     
    #5 tumbleweed, Aug 19, 2010
  6. FireEngineer

    FireEngineer Active Member

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    An engine block heater will help before leaving home in the morning. It will get your engine temp about 70F above ambient at start up, well into S4 full hybrid before your highway run. At work go ahead and start the car as soon as you enter it and let the car go through S1 while you are getting buckled-up and opening windows. Unless you can plug-in the EBH at work.

    Wayne
     
    #6 FireEngineer, Aug 23, 2010
  7. GBC_Texas_Prius

    GBC_Texas_Prius Member

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    My guess is that the aftermarket tires are the big killer. You have a lot of bicyclist in the area, right? Think like they do. Imagine how much effort they would have to exert if they went to fat tires.

    That's my tip, I try to think like I would if I'm bicycling.

    Also, for short trips, calculate how much you are spending in gas each day. If it's 30 cents, then don't worry about it, if it's $3, then finding an improvement may be worth while.
     
    #7 GBC_Texas_Prius, Aug 23, 2010
  8. bisco

    bisco cookie crumbler

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    how about one of those hats with the fan on the brim?:D
     
    #8 bisco, Aug 23, 2010
  9. austingreen

    austingreen Senior Member

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    I have a fat tired bike and a thin tired bike. Even my fat tires (2.5") make the stock prius's look huge. My thin tires (21mm) make it hard to control at slow speeds or fast turns. hehe. I have a friend that just sold his car to force him to ride. He s trying to get in shape for a 100mi trail run in Colorado. I think the wheels/tires give me trail race. I think my tires cause a 1-4mpg hit. Short trips in the heat cause more than 10mpg hit. I think I'll keep my fat tires on the prius.

    No its not much per day, as I don't take a big hit leaving home in the morning, its driving for lunch or and home from work or little errands on the weekend. I just was looking for some easy advice to see if my driving technique would help.

    Thanks. I'm going to try waiting S1 for a few days driving home this week and see how it compares. Morning is not as bad of a hit as the car is coming from a cooler garage. I can't plug in at work.

    I was thinking about one of those little fans in a cracked window. Would love the remote ac from the sun roof car, but didn't want leather and it was a long wait and and no dealer discount in a III.
     
    #9 austingreen, Aug 24, 2010
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