TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Crosswinds have big impact on range/Does this sound right?

Discussion in 'Texas' started by SoTX_WestTX, Dec 14, 2014.

  1. SoTX_WestTX

    SoTX_WestTX Member

    Joined:
    Jul 14, 2013
    Messages:
    80
    Location:
    Lubbock, TX
    When drove back to Lubbock from taking delivery in Austin, I charged in Abilene. I left with 200 miles of range, figuring that was enough cushion for the 170 mile drive. I pulled into my garage with 10 miles left, and learned that driving 75 mph doesn't get you a 1:1 miles-driven-to-range-used ratio, haha.

    I drove to Abilene this weekend and had two wildly different range usages. From Lubbock to Abilene, I decided to go 65 mph to see what effect that would have on range. I did the 170-ish miles with 296 w/mi average and using 185 miles of range. Coming back, I used 245 miles of range at 412 w/mi. Talk about being glad I decided to top it off before I left!

    Abilene to Lubbock is uphill, elevation change is about 1,500 ft. so I imagine that plays a part. There was also a 25-ish mph crosswind most of the drive. Would those two things account for that drastic of a difference? (I'm assuming that IS a drastic difference.) I wouldn't think a 5 mph difference in speed wouldn't be THAT big of a factor.
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,763
    Location:
    Texas
    The crosswind will be a far larger factor than the elevation gain. Wind is harmful to range for about 3/4 of the way around the car. Assuming the 360 degree mark is at the front of the car, anywhere from 125 degrees to 235 degrees is harmful. A 65 mph speed and a 25 mph crosswind will take about 26 kW of energy. At a zero wind speed it will be about 18 kW.
     
  3. TexasEV

    TexasEV Active Member

    Joined:
    Jun 5, 2013
    Messages:
    3,789
    Location:
    Austin, TX
    The elevation difference would cost you (or gain) about 10 miles of range. Figure 7 miles range per 1000 feet. Air resistance increases with the cube of the speed, so you can see why a 5 or 10 mph difference in speed really makes a difference with energy use. Of course it does in an ICE too, but we're not paying attention to range so closely in an ICE.
     
  4. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Joined:
    Feb 27, 2009
    Messages:
    5,062
    Location:
    Colorado
    Wind resistance increases as the square of speed. Energy is force times distance, so energy usage per mile (km) due to wind resistance also increases as the square of speed. Power required to go a given speed goes as force times speed, so increases as the cube of speed. This is a common confusion.
     
  5. SoTX_WestTX

    SoTX_WestTX Member

    Joined:
    Jul 14, 2013
    Messages:
    80
    Location:
    Lubbock, TX
    Thanks, guys! I figured headwinds, sure, just hadn't thought about crosswinds. I had been worried that going 65 mph on a 75 mph road would be a bit dangerous, but it didn't turn out so bad.

    Unfortunately, I also learned that if you happen to hit a tumbleweed blowing across the road it will scratch your hood and bumper. :( #WestTexasProblems

    Not even 2,000 miles and barely 4 months old. I'm starting to wish I hadn't looked so I could pretend my car is still pristine, haha.
     
  6. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,763
    Location:
    Texas
    That's why I got paint armour on the entire car.
     
  7. stephenpace

    stephenpace VIN S00219

    Joined:
    Dec 22, 2011
    Messages:
    558
    Location:
    Houston, TX
    I always hated tumbleweeds because we moved into a new neighborhood in Midland and as the kid I was tasked with weeding them out of the yard. Not only do they prick you but they have very long tap roots. No joke, I once saw a tumbleweed the size of a Honda Accord blowing across the road. I recall a case were a guy ran over one, it got stuck under his car and dragged, and caught on fire and burned up his car.

    I've told people about tumbleweeds before that doubted they really existed.
     

Share This Page