[Budd]

Motorcycles get roughly double the mileage of a compact car, right? But cars are more than double the weight of what a bike plus rider weigh. What about motorcycle engines make them so inefficient. Is it the high RPM for quick acceleration? I would assume that a sportbike would be more aerodynamic than a car.

So, why aren’t there motorcycles out there getting 200mpg?

[ShannonG]

I think it’s the tendency to be heavier on the throttle. I dirve my Suzuki car like a granny; I drive my Suzuki motorcycle like a banshee.

I hear you though, and I’ve wondered the same thing many times. Many bikes are still carbeurated; would that be a factor? Compression ratios? Bikes are way higher compression engines than cars. It must take more gas to create that kind of combustions.
I’m just throwing ideas out there; I really don’t know.

[WeaponZero]

Just making a logical guess here but I would assume it comes from the fact that motorcycles are under higher stress from the riders and how we are on the throttle of a motorcycle vs a car. Not sure if compression ratio would factor in there. Compression ratio generally only tells you what octane fuel you should be running mostly.

[ShannonG]

I sounded SO SMART until you posted. Way to ruin my Thursday.

[Anonymous]

I read something about this before, and its due to two main reasons. first and most important is that a motorcycle + rider has a much higher coefficient of drag compared to a car. The coefficient of drag is defined as how much wind resistance an object feels compared to a solid plane of equal height and width. Most cars, especially fuel efficient compacts, are designed to minimize this drag, while the upright nature of a bike and rider leads to a much higher CoD, I think for example, a normal sedan has a CoD of 0.3, and a normal bike has a CoD of 0.7,
The other reason is that car manufacturers have spent a long time trying to make their engines more efficient, while in motorcycles, the focus has always been about power, not fuel efficiency, giving bike makers little incentive to shoot for super efficient engines.

[AaronMerlot]

I think it is the the weight that is the big difference.
This is what I drive/ride and my real world mpg
2007 Suzuki GS500f 58-63 mpg, weight 396.8 pounds, Horsepowe 47
2005 Suzuki Forenza 27-30 mpg,weight 2701 pounds, Horsepower 126
Car= 21 pounds per 1 horsepower
Bike = 8.42 pounds per 1 horsepower
http://en.wikipedia.org/wiki/Power-to-weight_ratio
just so you know I am not an engineer, I just play one on TV.

ShannonG what car do you drive?

[ShannonG]

I have an ’01 Suzuki XL7. It’s the world’s smallest 7 passenger SUV! I get the same mileage you do in your Forenza.

[Author]

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