xlr8r

The point of an aerodynamic small-engined scooter is to sell in an environment where small engines cost less in road tax, in insurance costs, and where it may be possible to ride them without a seperate motorcycle licence or when still too young to drive a car. In other words, Europe. The aerodynamics are there to appeal to younger riders, and to keep the rain off mature owners who have so far always driven cars and are not used to real weather. It's a cultural thing entirely: gas mileage has nothing to do with it. The point of big-engined cruisers, on the other hand, is so that the motor turns more slowly at a given speed and gives a relaxed and economical ride along with long engine life, which in a consumer society obsessed with this year's model is a point often ignored. The point of in-line fours is to provide acceleration above all other considerations, and assumes that fuel is a cheap and endlessly renewable resource. Therefore both cruisers and scooters will have a place in the future, but inline fours are approaching the end of their period of supremacy. Since you are in the US rather than Europe, stick with your Nomad and make it last.

nolaandy

I don't know what the mileage is on the "new style" large scooters. There are numerous details that affect mileage. In stop and go situations weight plays a bigger role than aerodynamics. Also, in traffic large engines will burn more fuel than smaller engines of similar efficiency. The importance of aerodynamics increases with speed. Around town it isn't a big deal.



The crossover between big engines and small engines under acceleration conditions varies a good bit (big HP engines work less to accelerate a given mass than smaller HP engines, so you have to work smaller HP engines harder). Again, a variety of factors are at work here.



No jaw flapping can predict the outcome. Real world experience would tell the tale.



The points of small-engined scooters are good mileage, small size, easy handling in cramped quarters, performance good enough to keep up with traffic, inexpensive to buy.



Perhaps a better choice than a scooter would be something like a 250 Ninja or 500 twin something-or-other. Economical to buy, cheap to operate, fast enough to get on the interstate.

TheFox

It's all about revs. That monster V-Twin spins at a much lower rpm at cruise speed than a 600, and because the fuel used is a factor of volume moved in a given timeframe rather than a simple measure of displacement, those big cruisers get better mileage than one might normally think. Also, because the torque curve is so much better down low, there's no need to use a lot of fuel to accelerate from a stop, saving even more.



I'm just a leatherneck ground pounder though; I don't have a fancy engineering degree or anything. I don't know what the hell I'm talking about.



--The Fox

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TheFox

Awesome breakdown. You get a gold star.



(Seriously. This is the most intelligent post I've read in a long time.)



--The Fox

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Mike_L

Ditto on the fuel mileage. I thought a Burgman or Silverwing would make a great commuter, until I saw the mileage. My Buell XB12R pulls in nearly 50mpg under my normal riding conditions and almost never dips below 40mpg on the street.

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'04 XB12R Firebolt
'82 Sabre V45
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'01 XR100R (wife's toy)

fumanchu

nice explanation. i hadn't considered the rpm/torque difference.

philosophize on bro man.

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Rubble

Who cares? The people who ride them find them to be fun, convenient modes of transportation. Ride what you ride and let others ride what they ride.



For the life of me I can't figure out why these things have to go under the microscope every three to four months.

Maybe it's because most people riding them tend to smile and have a good time. That's simply a product of being themselves and not giving a rat's ass what anyone thinks of thier ride.





Rub

dylanmo

I know good people who have worked for Boeing, and they all hated it with the fire of a thousand dying suns. I got talked out of Phantom Works that way.

fumanchu

thanks for the previous explanations about twins versus in-line four's, but it got me to thinking (using the explanations above as a reference)... 1500cc's at 3500rpm (the nomad's peak torque is around 3000rpm) is burning more than 600cc's at 7000rpm (my general in-town max), so i'm skeptical of the huge gap in fuel economies. i looked into the MO archives for some corroboration (anecdotal as it may be), and i found this excerpt from the classic tourer comparo 2003:



"OBSERVED FUEL MILEAGE:


BMW R 1200CL: 38.8Mpg


Harley Road King: 39.4Mpg


Kawasaki Nomad: 32.6Mpg


Victory V92 TC: 31.5Mpg


Yamaha Silverado: 37.9Mpg


*Note: Mileage was taken on a group test ride, with all bikes rotated through 5 test riders, over 300+ miles of mixed freeway, surface street, canyon and country roads. This is a very fair and accurate "Real World" situation, with all bikes measured at the same time."

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seruzawa

Fuel consumption also depends on throttle opening. A larger displacement engine may run at a smaller opening than a smaller engine thus evening out the fuel usage.



It's gonna take x amount of horsepower to push a bike through the air. Say it's a full sized naked cruiser. Whether that bike has a 1500cc engine or a 600cc engine it still takes x horsepower. Fuel usage will tend to be the same in comparable bikes despite displacement. This is why both 600cc and 1000cc sportbikes will run similar fuel mileage at the same speed. You gotta burn the same amount of fuel to develop the same horsepower in similarly efficient engines.



As another example I once put a larger countershaft sprocket on my KZ750 to reduce engine revs on the Interstate. My fuel mileage did not change one bit. It took the same amount of horsepower to push the bike through the air and thus used the same amount of fuel.



Having fewer cylinders, etc twins are capable of getting better fuel mileage than 4s because they have less internal friction. Just calculate the surface areas of two large pistons vs 4 small ones to see the comparison. Then you/ve got more cam bearings, rod bearing, etc. All increase internal friction.

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