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This is an honest question.

I have a car that gets 40mpg on the highway. The car weighs 2227 lbs. and has about 100hp & torque.

While cruisers can get about 50mpg but weigh far far less.
 

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My VW Golf TDI averages 46mpg. Highway only driving it will get over 50mpg. My Vulcan 900, which I baby, gets close to 50mpg. Maybe the bike manufacturers just aren't willing to do what it takes technology wise to increase the mileage.
 

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I've wondered about this too. Does the more cylinders in a car give it a better performance ratio? I figured that it does and that performance can either be tuned for speed or gas mileage. Not that I have any proof, just what I always thought...
 

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My VW Golf TDI averages 46mpg. Highway only driving it will get over 50mpg. My Vulcan 900, which I baby, gets close to 50mpg. Maybe the bike manufacturers just aren't willing to do what it takes technology wise to increase the mileage.
Again, aerodynamics!!! Wind drag! A person sitting on a bike going down the road is like attaching a parachute to the bike. Saddles bags increase drag. Space around the engine increases drag. Sticky compounds in the tires causes drag.

My little wedge shaped car, with the windows up, cuts through the air with the greatest of ease and gets fantastic fuel mileage.
 

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Again, aerodynamics!!! Wind drag! A person sitting on a bike going down the road is like attaching a parachute to the bike. Saddles bags increase drag. Space around the engine increases drag. Sticky compounds in the tires causes drag.

My little wedge shaped car, with the windows up, cuts through the air with the greatest of ease and gets fantastic fuel mileage.
Why do scooters get 80-100 mpg then. They are the same shape as motorcycles.
 

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I agree with the aerodynamics. My Ninja 250 was one of the best vehicles I've ever owned for gas. And my old 1991 Civic hatchback. A wopping 90hp in that thing! So I think engine size has a lot to offer as well.

Scooters have tiny engines usually, the ones getting that kind of gas mileage anyway.
 

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Again, aerodynamics!!! Wind drag! A person sitting on a bike going down the road is like attaching a parachute to the bike. Saddles bags increase drag. Space around the engine increases drag. Sticky compounds in the tires causes drag.

My little wedge shaped car, with the windows up, cuts through the air with the greatest of ease and gets fantastic fuel mileage.
Okay, I can see aerodynamics playing a bit of a factor at high speeds, but why isn't the city mileage better?
 

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Okay, I can see aerodynamics playing a bit of a factor at high speeds, but why isn't the city mileage better?
I dont think it's aerodynamics.

Why does a scion xB get good gas mileage then. It has a flat up and down windshield just going against the wind. That has more resistance than a slim human body. I would defintely think that a thin motorcycle can cut through the wind better than a boxed shape scion xB.
 

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Scooters get 80-100 mpg.
Scooters = pea size engine + slow speeds + narrow tires

Wind drag goes up as speed increases and it's not linear.

Narrow tires decrease rolling resistance.

CV transmissions/clutch keep the little pea sized engine on it's power curve most all the time.

Scooters don't sound good when you jump on the throttle :)
 

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I dont think it's aerodynamics.

Why does a scion xB get good gas mileage then. It has a flat up and down windshield just going against the wind. That has more resistance than a slim human body. I would defintely think that a thin motorcycle can cut through the wind better than a boxed shape scion xB.
Magic!
 

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Scooters have tiny engines usually, the ones getting that kind of gas mileage anyway.
My Honda Helix has a 250cc...not really a tiny engine. She will get 69mpg if I stay in the 55mph range.
The minute I push her out of that range (~70) then the milage drops to about 58mpg.

I have been wondering for years why there isn't a 100mpg bike. Some of these beemer cruisers and other sport tourers are pretty well areodynamic....considering the weight to hp ratio.

We need an engineer here.

Also...all these tuner computers that are added for new pipes...would any of them have settings to up your gas mileage? Even 3-4 miles per gallon could pay over time.
 

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V-Twin single pin crank engines have never been known for efficiency... and momentum and aerodynamics have a lot to do with it. I would guess that a rider on a motorcycle is subject to more wind resistance than a car, even if the car is larger... there was a great article in Hot Rod about 15 years ago explaining why a NASCAR car of the time had a higher top end speed than and F1 car... It was because the resistance from the air was pushing hard DOWN on the F1 car, but the big brick of the NASCAR car was "punching" through, allowing air UNDER it letting the force of the air go "through" it... Article did a much better job than I did of explaining it.

Also, think of it this way... take the size of the engine... in my case it's 1.6L in displacement (slightly less). The cylinders have to displace a certian amount of fuel per revolution. The ratio of gas to air will be drastically different depending on load of course... so, a 1.6 L car engine would get similar gas mileage as a 1.6 L engine (if the effeciency is the same), all other things being equal. Throw in the theory that car engines ARE more efficient (because they have to be), and the extra momentum from the weight of the car AT SPEED (less engine use needed to maintain level or downhill running), and the added wind resistance on the bike (maybe)... I can buy that motorcycles get the same as a good gas mileage car of similar engine size.

Take the same situation, a car and a motorcycle, hauling butt all over town in bumper to bumper traffic... I would guess (and know from personal observation) that the bike wins the gas mileage wars there... you have taken out the wind resistance AND the momentum advantage the car gets.

Anyhow, just an opinion from a bored guy on a quiet friday at work... wishing he was out on his bike.
 

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My Honda Helix has a 250cc...not really a tiny engine. She will get 69mpg if I stay in the 55mph range.
The minute I push her out of that range (~70) then the milage drops to about 58mpg.

I have been wondering for years why there isn't a 100mpg bike. Some of these beemer cruisers and other sport tourers are pretty well areodynamic....considering the weight to hp ratio.

We need an engineer here.

Also...all these tuner computers that are added for new pipes...would any of them have settings to up your gas mileage? Even 3-4 miles per gallon could pay over time.
I rode my 900 Classic LT in a charity ride where the police esscort only went 45 miles and hour. I filled up when it was over and got 65 mpg... my normal is around 55 so speed makes a difference.

I've seen several diesel bikes that get well over 100 mpg. There are a lot of guys repowering the Royal Enfield bikes with 403cc diesels and getting 130 or better.

I'm building a diesel bobber with one of the 403cc diesels; I hope to get better than 100 mpg using veggie oil.

Something like this Diesel Powered Bobber Chopper

Another cool site DieselBike.net The Original Diesel Motorcycle website.
 

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Could be because the motorcycle industries know the mind of the rider. If it was more fuel efficient, it would be slower off the line or top speed. Who would want that in a motorcycle?
Look how many people on this board that has done something on their bike to give it more power, increase torque, or speed because that's what they want.
Would you buy 900 cc bike that gets 75 mpg, IF it took 10 seconds to get to 60 and had a top speed of 60? Not me!
 
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