Gas mileage comparison to cars

[professor]

I am going to use my old Prisim (Toyota) as a comparison point, it gets about 30 mpg around town and weighs 2800# (race weight= includes driver and any junk in the trunk). Why doesn't a 250 pound bike and rider get 300 mpg?

 

[loquin]

bike/rider is less aerodynamic.

A small bike motor is a less efficient engine. Especially a two-stroke. Older two-stroke designs pump 25% (or more) of the fuel into the air, unburnt.

An auto uses a transmission to match the engine rpm to the ground speed, so that the engine is running in it's most efficient power band. Most bikes have a single gear ratio, meaning that the acceleration/top end speed are always compromises

Even with the lower efficiencies, a GEBE with a 25 to 33 cc motor can get over 200 mpg.

Also,

 

[professor]

Good answer Lou. Had not thought about gearing too.

 

[cabinfever1977]

Mine gets 180mpg, thats pretty good.

 

[motor_head]

the smaller the engine the more fuel it uses per hp, and as loquin said 2 strokes release alot of unburned fuel through the exhaust

 

[plinko]

I am going to use my old Prisim (Toyota) as a comparison point, it gets about 30 mpg around town and weighs 2800# (race weight= includes driver and any junk in the trunk). Why doesn't a 250 pound bike and rider get 300 mpg?

Where's Gilligan,Skipper,Mary Ann,Ginger,And Mr and Mrs Howell residing now?

 

[professor]

Saw an article on Mary Ann snagged for Mary Wanna posession.
My origional thought was the motorbike is about a tenth the weight of an economy car so should get ten times the fuel milage. But they don't.