Wind = reduced fuel mileage

[Rocker66]

I have noticed that the recent strong winds have reduced the fuel mileage that I'm getting on my commute quite a bit

 

[dduelin]

I agree. I refer to my 1000 mile ride yesterday where a stiff headwind brought the mileage down about 6 to 8 mpg.

http://nc700-forum.com/forum/nc700-...did-you-do-your-nc700-today-38.html#post10556

 

[Billy Budd]

Wind is concentrated air, more mass to push around the bike equals more energy required to do so.

 

[Naked_Duc]

I track my mileage in Excel and I also include temperature and rain. After 1 year and 8000 miles on the CBR, I can draw the following conclusion:

1) temperature makes a difference. Cold and dense air require more energy to push thru. Some might argue that denser air would enter the engine and create a bigger combustion. With a carb, it might be slightly true but with EFI, the CPU auto adjust for the mixture so there isn't any measurable gain in HP to offset the higher air / drag

2) wind and rain would only add to air you are trying to push the bike thru.

3) any sort of braking is a loss of kinetic energy. heavy traffic, stop and go, or frequent change of speed = bad mileage.

4) laws of aerodynamics: once you are in 6th gear, you should get the same mileage no matter the speed (RPM and speed is fixed) IF you are in a vacuum. The co-efficient of drag really picks up once the air flow becomes turbulent and that's at around 50mpg. so you want to maximize your MPG, slow down.

NOTE: being on the 250 for a year really changed how I ride. I am more conscious about being smooth and carrying speed thru turn. Anything can be felt on the bike since it's so light (360 lbs) and so low on power (24 hp).

 

[Daboo]

...The co-efficient of drag really picks up once the air flow becomes turbulent and that's at around 50mpg. so you want to maximize your MPG, slow down...

Back in the last century, the government pushed the speed limit down to 55 mph. The reason was to save gas, or that's what I remember. Anyway, the point is they published a lot of info on why it would save gas. I remember seeing a chart that showed how much gas you used as the speed increased. It was a pretty slow climb as speed increased...till you hit 60 mph. Once you passed 60, it increased dramatically.

In my non-engineering mind, it makes sense that if your airspeed increases (ground, plus head wind), you'll be using more gas, just as if you were actually traveling that much faster.

Chris

 

[Naked_Duc]

it's all about how the air flow over a surface. Air can flow over a surface smoothly at a low speed, even over some imperfection. As the speed picks up, the flow becomes turbulent. If the object has a high coefficient of drag (like a brick), the effect is even more pronounced. If I remember it correctly from my engineering class (we actually did an experiment in the lab), the transition point was at about 50 mph and 55-60 is when the turbulent starts (over smooth surface). After that point, the effect of drag (wind resistant) increases at the square of your speed - wind resistant at 200MPH is 4 times of that at 100MPH.

So when you add head wind, it compounds the problem - you need much more energy going against head wind than the energy you will save going with a tail wind.

 

[mike5100]

I think the styling of a bike will change over the next few years to reduce the drag. Leading the way are the electric bikes competing in the Isle of Man TT. I remember the guys who won last year did it by paying a lot of attention to the back of the bike and fairing in the riders legs so that air flow slipped smoothly off the back. It goes without saying that you need a good full fairing on the front of course. But then these riders are happy to crouch down behind the screen whereas your average rider will want to sit more upright. I think as riders we will have to take lessons from the cyclists and we'll hopefully get super slippery textile suits and more aerodynamic helmets.
Mike

 

[ducatievans]

I wish I had a moto2 front fender

 

[showkey]

I think the styling of a bike will change over the next few years to reduce the drag.....
Mike

There is and will always be a compromise with style vs drag vs costs vs is it sale-able ?

 

[SilverRocket]

If you knew you were going to be riding into high winds, and wanted the same mileage you'd been getting, would changing sprockets to lower the rpms help?
Not a practical solution, just wondering...

 

[670cc]

If you knew you were going to be riding into high winds, and wanted the same mileage you'd been getting, would changing sprockets to lower the rpms help?
Not a practical solution, just wondering...

Nope. Lowering the RPM might put your power output below what’s needed to maintain speed. Then you’ll just need to downshift, negating anything gained by the sprocket change. The work of pushing the wind has to be done. There will be an ideal RPM for the engine at your given speed, but the fuel economy is gonna stink either way.