dont understand fuel consumption disparity between car & bike

S

SkyRider

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so...

my dual sport bike gets 60 mpg
my suv gets 20 mpg.

suv has inline 6, 3 litre engine.
bike has 1 cyclinder 250cc engine.

bike has 1/12 the displacement
but fuel consumption is only 1/3 of the car

car weights 4850 lbs with driver
bike weights 470 lbs with rider
car weights 10x more, but fuel consumption is only 3x more.

so, seems like my bike's fuel economy isn't that great, OR, car's fuel economy isn't that bad...

thoughts?
 
SkyRider said:
the amount of effort u used to post that pic u could've wrote something actually useful, lol
Click to expand...

Okay...well....

You're assuming that there's some kind of semi-linear relationship between fuel consumption and the size of the vehicle/# of cylinders. There isn't.

/thread.

Have a nice day :D
 
I think he meant to say that there's no directly proportional relationship between fuel consumption and either engine displacement, cylinder count, or vehicle weight, which is what you are suggesting in the original post. But I would call them all semi-linear relationships.

A few things to consider; bike engines are in fact less energy efficient than car engines and secondly bikes are very aerodynamically inefficient for their size.
 
At 100 km/h in top gear, the engine in your SUV is probably turning at around 2000 rpm.

The engine in the 250cc bike is probably spinning at 6000 rpm at the same speed, maybe more.

It may be 1/12th the displacement but it's spinning 3 or 4 times as fast.

It also depends on how hard the engine has to work. How much air is the vehicle pushing aside as it moves? The truck has a lot more frontal area. The drag coefficient of the truck probably isn't great, but it's better than a bike plus rider.
 
to accurately compare, you would need to find a algorithm (right word?) including

drag coefficient
RPM
displacement
stroke/bore
weight
torque/HP
drag of the tires on pavement
rotational weight of the wheels

and probably more.
 
rukus said:
to accurately compare, you would need to find a algorithm (right word?) including

drag coefficient
RPM
displacement
stroke/bore
weight
torque/HP
drag of the tires on pavement
rotational weight of the wheels

and probably more.
Click to expand...

+1
There are lots of variables involved than just engine size and weight
 
fastar1 said:
I think he meant to say that there's no directly proportional relationship between fuel consumption and either engine displacement, cylinder count, or vehicle weight, which is what you are suggesting in the original post. But I would call them all semi-linear relationships.

A few things to consider; bike engines are in fact less energy efficient than car engines and secondly bikes are very aerodynamically inefficient for their size.
Click to expand...

Yea, this is what I meant. Good catch :D
 
The passenger weight to vehicle weight ratio is what throws it off. Say you weigh 1/2 as much as your bike, that's bad.
If your SUV weights 5000 lbs, and you weight 2500, fuel mileage is going to suck. Now lift your weight off the bike, with a pillow,
mileage will roughly double. Pillow in the SUV - no dice.
 
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