Crosswinds/Headwinds/Tailwinds!

[pletby]

Hey Guys, just got home from a long ride in a very strong quartering headwind highway ride. I didn't get very good mileage at all, even though conditions warranted lower speeds due to ice buildup on the highway and bad visibility in blowing snow. Usually at 75ish km/hr I get awesome mileage (40mpg) but today was 24.2mpg for the trip. I actually got 27ish as I turned directly into the wind. Winds were NW 35 gust 48 km/h. I was driving north.

I'm finding that a quartering headwind is the worst for mileage. Does anyone else find this?

Last week I got an awesome tailwind and got 50mpg for most of my trip driving at 90km/hr. Happy!

[Frank Lee]

It's true, the quartering headwind is even worse than a straight headwind. Sounds just like the trip I just took- I'm sure it'll be an awful tank even though I slowed down to 50mph for about 300 miles. And the wind was so STRONG!

[turbothrush]

Yep ..I have had an MPGuino in my Civic vx for almost 3 years now. And your right the wind makes a huge difference. Like as much as 10 mpg for me in a strong wind. Because of this I try to mention the wind in my fuel log so as not to lead people astray (I have a long commute) . I get 58 mpg at 60 mph with 0 wind ,flat road, 65 -70 degrees. If I read 62 mpg on the mpguino I have tailwind . Simple as that. And yes headwind in Yaw is worse than direct headwind

[MetroMPG]

Makes sense - a quartering headwind will encounter a dramatically larger "apparent" projected area, and the Cd of the vehicle at that wind angle will be horrible.

[mort]

In addition at least 2 tires are forced to skid.
-mort

[skyking]

I think a quartering headwind will spank the trailer jockeys even worse. The way the relative wind tries to get through the gap, and also you would lose any semblance of air passing over the tow rig and onto the trailer nicely, sans a tight fairing system.

[kurzer]

you need a 4WS car and fiddeling with the controls, to make the car runs like a dachshund...

[slowmover]

Yesterday was doing some errands. Against the wind (almost a headwind) saw the overhead cut 6-mpg in one direction . . and on the return trip saw an increase of 10-mpg over the "norm". Boy, was it quiet on the return leg. A steady 25-30 mph wind with gusts past 50-mph will do that, ha!

Small craft warning advisories for the Bay and surrounding waters is always worthy of note in reading weather forecasts, but the warnings about tall road vehicles is quite another level. One has to expect that any vehicle may wander into ones' lane, even the low and aero with prevailing side winds and gusts. Folks tend to over-correct at the wrong moment. Distractions from being lane-centered are of more serious consequence.

.

[JRMichler]

There's a graph in Hucho showing wind tunnel data for drag vs wind direction. The worst drag was with a direct crosswind.

[Diesel_Dave]

Here's some of my own historical data:


This is average mileage vs releative wind direction. 0 deg is a direct headwind, 90 deg is direct crosswind from the right, 180 deg is a direct tailwind, etc.

This was ~150 days worth of data, where I filtered out days with wind speeds <5 mph, and then rounded the relative direction to the nearest 45 deg.

There's obviously some noise, but generally it looks to me like it follows the "conventional" thinking that direct headwind is worse, direct tailwind is best. Of course, this plot doesn't take wind speed into account, or temperature, or rain, or traffic, or other things, etc...

I've also noticed that wind direction often correlates with temperature, i.e., a south wind usually accompanies higher temps; a north wind generally means colder. FYI, my morning commute is SSE, evening is NNW.