214 mpg motorcycle and add 13 mph to the top speed to boot!

[forester]

Imagine what could be done on a larger bike?

http://ecomodder.com/blog/diy-aero-fairings-honda-125cc-motorcycle-214-mpg/

Awesome!

[Kraz]

Imagine what could be done on a larger bike?

Guzzi, for the win!

[forester]

That is a pretty sweet fairing for such an old galopy I have to admit.

[Rincewind]

Imagine what could be done on a larger bike?

http://ecomodder.com/blog/diy-aero-fairings-honda-125cc-motorcycle-214-mpg/

Awesome!

But wouldn't a larger bike negate a lot of that high-efficiency that the lightweight 125cc is capable of getting?  

[Giaka]

Ninja 250? They get 60 to 70 mpg in stock form. Wonder if we could double that?

[Kraz]

That is a pretty sweet fairing for such an old galopy I have to admit.

I think the V-8 might use too much gas though...

[Oxblood]

If you want to see something cool, look up Tom Mellor. He is a local Vancouver rider who has competed in speed races down at Bonneville. He has set numerous records on a partially modified Triumph 750. I forget what year but I melieve early to mid 70's. The only mods are a disc style front wheel, and hand made aerodynamic fairing. It is trick looking bike. The one in that post is just some hipster's idea of making his sub-scooter/moped cool.

[lharrell79]

I would think a larger motor would equate to higher speeds.  At higher speeds, resistance is going to come into play, and MPG's will decrease significantly.

Lucas

[AutoXer]

Don't forget the work being done by Craig Vetter, he's been doing this for years.

[Busa@11K]

But wouldn't a larger bike negate a lot of that high-efficiency that the lightweight 125cc is capable of getting?  

Any vehicle is going to get better gas mileage with less air drag.  When a vehicle is at constant speed, the weight of it only effects the power required to overcome the rolling resistance.  All the rest of the power is used to overcome aerodrag, which is the majority of the power used.

If you could take away all the air drag, everything on the road would be getting huge increases in gas mileage.

[Baz]

Read an article a while back on the wind resistance of a motorcycle.

It appears that the most slippery stock bike at the time of testing (The Hayabusa) had wind resistance equivalent to an average sedan.

The power required to increase top speeds had to climb in huge multiples for that reason.

[Busa@11K]

Read an article a while back on the wind resistance of a motorcycle.

It appears that the most slippery stock bike at the time of testing (The Hayabusa) had wind resistance equivalent to an average sedan.

The power required to increase top speeds had to climb in huge multiples for that reason.

Here's a comparison between a slippery bike and a slippery car.

Hayabusa: Cd = 0.56, frontal area = 6.0 ft^2
Gives a CdA of 3.36 ft^2

C5 Corvette: Cd = 0.33, frontal area = 20.7 ft^2
Gives a CdA of 6.83 ft^2

The Cd on the bike is a lot worse, but the frontal area is a lot less, giving a CdA about 1/2 of the car's.  The CdA is what really counts when it comes to defining the aerodynamic drag of the vehicle.

BTW - the HP needed to overcome aerodynamic drag increases as the cube of the velocity ... so you need tons of HP to go really fast.  

[Kraz]

Read an article a while back on the wind resistance of a motorcycle.

It appears that the most slippery stock bike at the time of testing (The Hayabusa) had wind resistance equivalent to an average sedan.

The power required to increase top speeds had to climb in huge multiples for that reason.

   I don't know if I buy that - no average sedan with 200hp does 200mph... I think it's the wind resistance (or lack thereof) that allows a 200hp bike to do 200mph... or am I missing something?

[Baz]

I don't know if I buy that - no average sedan with 200hp does 200mph... I think it's the wind resistance (or lack thereof) that allows a 200hp bike to do 200mph... or am I missing something?

Power to weight ratios come into play also. 200 hp works better in a 500 lb vehicle vs a 4000 lb vehicle.

Here's a comparison between a slippery bike and a slippery car.

Hayabusa: Cd = 0.56, frontal area = 6.0 ft^2
Gives a CdA of 3.36 ft^2

C5 Corvette: Cd = 0.33, frontal area = 20.7 ft^2
Gives a CdA of 6.83 ft^2

The Cd on the bike is a lot worse, but the frontal area is a lot less, giving a CdA about 1/2 of the car's.  The CdA is what really counts when it comes to defining the aerodynamic drag of the vehicle.

BTW - the HP needed to overcome aerodynamic drag increases as the cube of the velocity ... so you need tons of HP to go really fast.  

A Bang on explaination. Thank you Mr. Busa!

In The case of the Buggati Veyron, (Worlds fastest production car) They only require 270 HP to get the car to 155 mph, but require 1001 hp to get it to its top speed of 253 mph.

Explained here.




Incidentally they had to add 199 HP to the Veyron just to get an additional 5 mph out of it to keep its fastest car title.

[Busa@11K]

Power to weight ratios come into play also. 200 hp works better in a 500 lb vehicle vs a 4000 lb vehicle.

Power to weight only matters during acceleration ... as does of course also aerodynamics at the higher end of the acceleration period.

Only thing that really matters at a near constant speed is aerodynamic drag and rolling resistance (which is somewhat dependent on the vehicles weight).

[spd2918]

When speed doubled, drag quadruples (iirc).

[Busa@11K]

When speed doubled, drag quadruples (iirc).

True .... because aerodynamic drag force is a squared function of velocity.

Required HP is a cubic function of velocity ... so if the speed doubles, the required HP needs to increase by 8 times.