Has anyone measured the impact of wind on FE? - Page 2 - GreenHybrid

leahbeatle · #11 (**permalink**) 12-04-2006, 02:05 PM

Quote:

Originally Posted by twuelfing

the Power being referred to is irrelevant of the means of propulsion. Basically the amount of energy needed to be put into the system to maintain speed increases as the cube of the speed. This is irrelevant to what the object is or what is powering it.

its all about relative air speed, the lower the relative air speed the better off you are.

but if your driving 55 into a head wind of 20 your relative air speed is 75
conversely if you have a tail wind of 20 your relative air speed is 35

since we have that issue of drag increasing as the square and power required as the cube you can see how you will never be able to gain anywhere near the amount of energy into the system from a tail wind as you will lose from a head wind.

I am not sure that you were actually taking the post in the wrong way, but it seemed as though you are implying that the statement I previously made may not be applicable to a motor vehicle because somehow the fluid dynamics of the vehicle aren't linked to the amount of energy required to move the car, however I am probably just misreading your post. and my reply then will have been all for nothing.

No, no, I was agreeing with you. You're quite right.

I was just complimenting you for talking about physics, and throwing in my own two cents (air resistance independent of propulsion method) while I was at it.

Pbaker · #12 (**permalink**) 01-02-2007, 09:16 PM

I just drove from Los Angeles to Phoenix, and on the way to PHX, with almost no wind we got 45mpg. On the way back to LA with approx 40-50mph head winds we only got 40mpg. Both ways with myself, my wife and 3 small kids in the car. 07 Civic Hybrid. 1300 miles, now.
Not very sceintific, but it kinda makes sense to me.

bear15 · #13 (**permalink**) 01-19-2007, 07:55 PM

I just returned from a 700 mile trip-- 350 miles each way (mostly highway). I was able to pull off 61.1 mpg. On the way to the location I had a strong 15 to 25 mph head wind and I kept my speed to btw 55 to 60 mph and stayed a distance behind a tanker truck to avoid small stones and debris (I averaged a little more than 49 mpg). On the way back, I had a similar 15 to 25 mph wind but from the side (west wind as I was traveling north). This time I kept the speed btw 60 to 65 mph and I was able to be a bit closer in my drafting as small stones and debris on the shoulder were not a factor (I averaged a little more than 71 mpg).

I am beginning to learn a few tricks for safely driving in strong wind and still receive acceptable FE. For example, if cross winds are from center median toward right shoulder, debris from big trucks is not as much of a factor as the debris is blown off the highway and not onto my car.

I was very happy with 61.1 mpg especially for mid-January with temps around 20°F.

Quote:

Originally Posted by Pbaker

I just drove from Los Angeles to Phoenix, and on the way to PHX, with almost no wind we got 45mpg. On the way back to LA with approx 40-50mph head winds we only got 40mpg. Both ways with myself, my wife and 3 small kids in the car. 07 Civic Hybrid. 1300 miles, now.
Not very sceintific, but it kinda makes sense to me.

Anahymbrid · #14 (**permalink**) 01-21-2007, 11:29 PM

Quote:

Originally Posted by bear15

I averaged a little more than 71 mpg)... I was very happy with 61.1 mpg especially for mid-January with temps around 20°F.

71 mpg with a cross wind in 20 degree temps? I bow to your greatness! The best I've done for more than 100 consecutive miles at those speeds in mild summer temps (no a/c) is 60 mpg with a good draft!

Are you sure you didn't have a tow rope attached to that truck?

leahbeatle · #15 (**permalink**) 01-24-2007, 04:46 PM

Gotta agree with Anahymbrid, here- that is truly impressive, bear15!

Doberwiler · #16 (**permalink**) 01-27-2007, 03:35 AM

Folks,

We have a 2006 Honda Pilot which can shut down the 3 back cylinders to save fuel and we have a newer 2007 Civic Hybrid. I think I can shed some real world light on the wind subject...

We drove the Pilot from Boston to SF when we moved -- it was a brand new car. Best Mileage we got was around 24 -- not bad for an SUV going 75-80.

This holiday season, we drove the Pilot from SF to Dallas and back. Crossing TX I got the best Mileage I ever got 24.5, and it was flat (cruise at 78). It was in 3 cylinder mode the entire time. I was in heaven.

On the way back through Taxas, the Pilot never went into ECO mode shutting down the cylinders – I thought something was wrong. When I needed gas, I got out and the winds were stopping me from opening the door! That tank was 17.4 MPG on the highway!

The Pilot is not as aerodynamic as the Civic, and the winds are not as extreme for you. But wind can certainly sway your mileage a large amount – a 30%-40% difference depending on how you want to do the math.

Dobe

IMAhybrid · #17 (**permalink**) 02-01-2007, 12:11 PM

I had a terrible head-wind on the 3 hour drive home from my dad's house today. I got 49.9 MPG at 60 on the highway. I usually can do much better.

leahbeatle · #18 (**permalink**) 02-02-2007, 03:09 PM

Well, that's annoying, but look on the bright side- 49.9 is nothing to be ashamed of.

bear15 · #19 (**permalink**) 03-04-2007, 05:46 PM

We are planning a long trip next week and we hope we have a strong tailwind in both directions.

tanstaafl14 · #20 (**permalink**) 03-05-2007, 02:06 PM

Last winter I drove home from work into a 30-mph headwind. Had to watch helplessly as the MPG meter spiraled downward (at least 5 MPG over the 60-mile trip).