Big Fuel Penalty in Head / Crosswind conditions

[ChewChewTrain]

Originally Posted by OliverGT

I know this is good information to have, but I'm not quite sure what changes or decisions you could make having this information. Although I suppose at the very least it would let you know why your MPG for a certain trip was not as good as it should be.

Oliver.

I would use this information to know if it was economical to drive to the supermarket. If not, I would simply wait a month until the wind direction was more favorable to get much needed infant formula.

[ChewChewTrain]

Originally Posted by Draigflag

The original topic is here with my results. I saw an epic 20% dive in strong headwinds with added rain just to rub salt in the wound!

http://www.fuelly.com/forums/f8/headwind-18370.html

Thanks. That was a very interesting discussion.

[Draigflag]

Maybe a pitot tube would work? Although it only points in one direction, you could at least determine if there was a headwind or not? I don't know, probably don't know what I'm talking about...

https://en.wikipedia.org/wiki/Pitot_tube

[ChewChewTrain]

Originally Posted by Draigflag

Maybe a pitot tube would work? Although it only points in one direction, you could at least determine if there was a headwind or not? I don't know, probably don't know what I'm talking about...

https://en.wikipedia.org/wiki/Pitot_tube

Yeah. Measuring crosswinds would require a separate instrument.

Paul, how well does the Insight drive without the battery connected?

[Draigflag]

It's a bit slow Doug, but it was never a fast car to begin with! Requires lots of high revs, something I've not done since having a low revving torquey diesel. Still, I tackled a steep hill at 70 MPH in 3Rd gear with a passenger no sweat, lightweight construction has lots of plus points.

[Charon]

Originally Posted by OliverGT

Charon,

Not quite sure how this would work, given that the car is moving through the air as well as the air moving relative to the ground.

Maybe if you had something like an aeroplane, where you get both ground speed and air speed, where airspeed will include any tail/head/side wind. it still doesn't really give you side wind information though.

I know this is good information to have, but I'm not quite sure what changes or decisions you could make having this information. Although I suppose at the very least it would let you know why your MPG for a certain trip was not as good as it should be.

Oliver.

In an airplane in flight, unless you are slipping it, the airflow is always directly along the axis of the airplane. The pitot tube points directly forward and gives the airspeed. There is no direct way to measure ground speed, although GPS now does that (doppler radar can also do it). Airplanes almost always fly at least a little "sideways" to correct for side winds. In planning a flight, the pilot uses the forecast winds, the airspeed of the aircraft, and the desired direction of flight to calculate the resultant ground speed and the crab angle (the angle at which the airplane is pointed into the wind). The reverse calculation could be used given the ground speed and the angle of the wind to calculate the wind speed and direction. Not that it matters in a car, because there isn't much you can do about it.

Articulated trucks (semis) and trains are particularly affected by crosswinds, because the crosswind "blows away" the hole the front unit makes in the air, so the following units (trailer, train cars) are affected by the air more than if the airflow were straight along the axis of travel.