Topic: Why Bikes Really Get Lousy Fuel Mileage - All Things Considered

[BobbyR]

I have often said that Motorcycles are really ineffcient, considering how little weight you are moving compared to a car. Here is an article that explains the science behind why you get the mileage you do.
This is not about how much mileage you get, IT IS ABOUT WHY YOU GET THE MILEAGE YOU GET.
Nice article, read and enjoy: http://www.motorcyclecruiser.com/tech/0905_crup_motorcycle_fuel_economy/index.html 

[myhondas]

Very interesting reading Bobby....thanks

[HavocTurbo]

I really like this part....

Despite being much narrower than any car I can think of, including Formula one and Indy cars, motorcycles have coefficients of drag that are on par with your average cross town bus, and that is exactly what puts the bricks to us when it comes to fuel economy.

[BobbyR]

I really like this part....

Despite being much narrower than any car I can think of, including Formula one and Indy cars, motorcycles have coefficients of drag that are on par with your average cross town bus, and that is exactly what puts the bricks to us when it comes to fuel economy.

I did also, it shows the dymanics involved as we ride. We punch a big hole in the air it seems.

[Gordon]

I've always been kind of curious as to how much of a difference in aerodynamics my windscreen makes when I have it on my bike in the Winter.  I'm sure it helps at least a little bit since the air is going around and over a smooth, curved piece of plastic instead of slamming straight into my chest and shoulders. 

[IAmCitizenMe]

Very interesting, indeed. Thanks.

A properly designed windshield offers better protection and reduces drag.

What would be a properly designed windshield for our CBs?

[Gordon]

Very interesting, indeed. Thanks.

A properly designed windshield offers better protection and reduces drag.

What would be a properly designed windshield for our CBs?

I think anything that's not just a flat board acting as a sail is probably better than nothing when you're talking about streamlining. 

[HavocTurbo]

I would assume the difference could be felt, just like laying down on the tank vs. sitting straight up with no shield.

One thing that always interested me was.... How come no one uses wind tunnels for bike design? Especially for high end sport bikes?

[Gordon]

One thing that always interested me was.... How come no one uses wind tunnels for bike design? Especially for high end sport bikes?

Who says they don't? 

[HavocTurbo]

Well you know what happens when you assume.... 

I worked for Kawasaki for about 5 years. Corporate and in a dealer. Not once (and I looked) could I find evidence that they used a wind tunnel for fairing or body work design.

I've called and talked to techs, directors in charge of design, even know a few higher up's that could find out for me. I wanted to watch one in action.

So maybe I'm wrong and this is top double secret probationary stuff?

[TwoTired]

What would be a properly designed windshield for our CBs?

The frame mount types are more stable than the bar mounted ones.

Lot's of Vetter's out there.        But, wheels are meant to be re-invented.

With the Vetter's I have, you feel the wind at your >>>back<<, pushing you forward.

[mystic_1]

From the article:

In John's case, his ACE 750 gets roughly 33% better mileage than his car, which all things being equal, would be considered a stellar improvement if we were comparing apples to apples. But as he points out, the car weighs considerably more than the bike, and I'd add that it can also accommodate four people, so it's no surprise he's questioning his bikes fuel efficiency, and he's by no means alone in that.

That's a bit of a red herring, the fact that the car _could_ accommodate four people.  If you actually put four people into the car, the fuel economy goes down.

Since we're comparing apples to apples, I'd say we should be comparing the amount of gas required to move a person from point A to point B, all other things being equal.  On that basis motorcycles are more efficient than cars as there's less extra weight that has to be moved along with the person (weight of the vehicle).

mystic_1

[super pasty white guy]

here's a interesting bit on the Moto Guzzi wind tunnel research program

http://thenewcaferacersociety.blogspot.com/2008/08/youtube-moto-guzzi-wind-tunnel-rolling.html

spwg

[TwoTired]

Want better fuel economy?  There are quite a few techniques/ides here:
http://www.craigvetter.com/pages/470MPG/Vetter%20Fuel%20Economy%20Contests.html

[CaféElite]

here's a interesting bit on the Moto Guzzi wind tunnel research program

http://thenewcaferacersociety.blogspot.com/2008/08/youtube-moto-guzzi-wind-tunnel-rolling.html

spwg

I was going to mention that as well.. I think I recall first seeing that in the Long Way Down euro TV show where Ewen Mcgregor (sp?) rode that BMW. One of places they stopped was there I think.

[BobbyR]

From the article:

In John's case, his ACE 750 gets roughly 33% better mileage than his car, which all things being equal, would be considered a stellar improvement if we were comparing apples to apples. But as he points out, the car weighs considerably more than the bike, and I'd add that it can also accommodate four people, so it's no surprise he's questioning his bikes fuel efficiency, and he's by no means alone in that.

That's a bit of a red herring, the fact that the car _could_ accommodate four people.  If you actually put four people into the car, the fuel economy goes down.

Since we're comparing apples to apples, I'd say we should be comparing the amount of gas required to move a person from point A to point B, all other things being equal.  On that basis motorcycles are more efficient than cars as there's less extra weight that has to be moved along with the person (weight of the vehicle).

mystic_1

I think you are missing the point. The motorcycle will always be handicapped vs the car. The inherent design makes it so, and there is very little that can be done about that. If we use the industry standard of fuel useage per ton mile, the bikes still lose. As pointed out in the article you can make a very areodymanimc bike, but it would not be very rideable under many conditions.
We have to live with the fact while we may use less fuel from A to B than in our cars, we are still not efficent. Nonetheless an interesting explantion of the dynamic forces on a Motorcycle at higher speeds.

[grumburg]

Guess that is why my S90 gets so much better mileage than my 550. Less wind resistence at 45 vs 70 MPH.   What is a Honda Orbit?

[Tretnine]

Interesting read. Seems like I could get better mileage if I really wanted, but I'm too fond of looking cool and am entirely unwilling to make my 550 look like an acrylic spearhead.

[Bob Wessner]

What is a Honda Orbit?

[mystic_1]

I think you are missing the point. The motorcycle will always be handicapped vs the car. The inherent design makes it so, and there is very little that can be done about that. If we use the industry standard of fuel useage per ton mile, the bikes still lose. As pointed out in the article you can make a very areodymanimc bike, but it would not be very rideable under many conditions.
We have to live with the fact while we may use less fuel from A to B than in our cars, we are still not efficent. Nonetheless an interesting explantion of the dynamic forces on a Motorcycle at higher speeds.

Meh.  Twiddle numbers all you like, but if a given trip from A to B uses less fuel on a motorcycle than in a car, that's efficiency to me.  How do you define "not efficient"?

Sure, cars are more aerodynamic, but in the car you're hauling around a thousand pounds or so of extra weight.

mystic_1

[grumburg]

What is a Honda Orbit?

Thanks Bob!

[tramp]

my old 750 get about 48mpg
thats plenty good for me
i like the wind in my chest
and finally, can you really compare riding a bike to driving a car?
i think not

[Gordon]

We have to live with the fact while we may use less fuel from A to B than in our cars, we are still not efficent.

I have to disagree.  It all depends on how you look at it.  Considering that the whole point of using the car or motorcycle is to get yourself from one place to another, anything that uses less fuel to do this is more efficient than something that uses more fuel.  Sure a car can move 3,000 pounds more efficiently than a motorcycle can move 500 pounds, but the point of driving a car or motorcycle somewhere isn't to move the most total weight, it's to move you. 

[Joel]

I think you are missing the point. The motorcycle will always be handicapped vs the car. The inherent design makes it so, and there is very little that can be done about that. If we use the industry standard of fuel useage per ton mile, the bikes still lose. As pointed out in the article you can make a very areodymanimc bike, but it would not be very rideable under many conditions.
We have to live with the fact while we may use less fuel from A to B than in our cars, we are still not efficent. Nonetheless an interesting explantion of the dynamic forces on a Motorcycle at higher speeds.

Meh.  Twiddle numbers all you like, but if a given trip from A to B uses less fuel on a motorcycle than in a car, that's efficiency to me.  How do you define "not efficient"?

Sure, cars are more aerodynamic, but in the car you're hauling around a thousand pounds or so of extra weight.

mystic_1

It depends on how you define the efficiency.  If defined as the fuel per person to move one person from A to B, the motorcycle will use less fuel than the automobile and would be considered more efficient.  With more people, it changes.  The motorcycle makes some trade-offs, like aerodynamics, but makes up for it in weight savings.  Thus for the stated goal of moving a single person from A to B, the motorcycle uses less fuel and is more efficient.

[HavocTurbo]

Haha 2 posts in a row that say EXACTLY the same thing only with different words.


WOOOHOO!!!