Mileage: Auto vs. Motorcycle - Kawasaki KLR 650 Forum
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post #1 of 13 Old 04-12-2012, 02:10 AM Thread Starter
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Mileage: Auto vs. Motorcycle

Another thread on here about KLR mileage made me think of this again: didn't want to jack it.

Perhaps it's just because I don't have very much smartness, but this whole scenario makes no sense to me. Can anybody explain it?

Consider my 4-wheeled vehicle and my KLR:

4WD Toyota Tacoma:

Large front surface area (drag)
4 large tires
Curb weight: 3877 pounds
142 hp 4-cylinder engine
MPG: 22

2009 KLR650
2 small tires
Curb weight: 460 pounds?
37 hp engine
MPG: 45-50
(Approximation: I've never checked it but have a lot of crap hanging off of it and I'm fat.)

Wouldn't you think, comparing the sizes of the engines and the weights, that the KLR would obtain significantly more mpg than the Toyota? I mean, it weighs about, what, a 12th as much or so but only gets about twice the mpg?

An even more dramatic example is the behemoth my wife drives, the 2005 Durango:

4500 pounds with a 330 hp engine, basically 10 times the weight and roughly 9 times the horsepower of the KLR.

Average 15 mpg. The KLR only does about 3 times better than that.

I'm stumped: would explain why I'm not an automotive engineer, I guess.

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post #2 of 13 Old 04-12-2012, 09:45 AM
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I'm not an automotive engineer, and I'm fat, too..

But my guess is wind resistance.. I dunno..

Just to add to the issue.. I had a FZ6.. Even less engine size than a KLR, made 3 times the horsepower than the KLR, and got 5mpg less than the KLR does..

On the other hand, it was pretty..
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post #3 of 13 Old 04-12-2012, 09:56 AM
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Bikes have absolute crap for aerodynamics. Throw a bike and a rider in a wind tunnel, and you can see some serious FAIL!
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post #4 of 13 Old 04-12-2012, 10:06 AM
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Originally Posted by thetable View Post
Bikes have absolute crap for aerodynamics. Throw a bike and a rider in a wind tunnel, and you can see some serious FAIL!
That as well as the autos mentioned have complex fuel injection systems with computers and sensors that are constantly doing calculations to achieve best mpg ratings.

The Klr however just has a carb. No sensors or any fuel monitoring. Just jet size controlling fuel.

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post #5 of 13 Old 04-12-2012, 10:35 AM
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Motorcycle engines are generaly tuned for performance vs. fuel economy. BTW they also generate more polution than a car as a result. More sophisticated fuel delivery/ignition mapping can improve the mileage but most riders want the performance. Consider the power to weight ratio of a motorcycle vs. a car.

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post #6 of 13 Old 04-12-2012, 10:36 AM
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I think it is largely aerodynamics.

My KLR is averaging 44mpg tracked of about 9,600 miles. My BMW, with twice the horsepower and driven about 10mph faster, is averaging 41mpg tracked over about 11,300 miles.

I have an F-250 4X4 with a manual transfer case and hubs, 4.30 rear end, V10 with about 310 horsepower. That thing will get 15mpg on the freeway if I run at 62mph (trucker speed).

Today's cars and trucks have some pretty good aerodynamics! Motorcycles, not so much.


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Last edited by Tom Schmitz; 04-12-2012 at 10:54 AM.
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post #7 of 13 Old 04-27-2012, 06:02 AM
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Good points on the aeros, gents.

Other than the totally slick fairing, it's a bumpy mess on our scooters.
The wide cowling/ air ram into the radiator is a gaping forward facing parachute, the mirrors, brushguards, feetpegs, riders' legs, elbows, windshields,
side luggage, etc all contribute to air braking. Another factor is the
vaccuum in our wake trying to pull us back to a lower speed. (tail cowls
are a huge bonus on cafe' racers) We sit upright with dead air/ turbulence
behind the spine also causing a flow void.

The Geo Metro of the mid 90's got 50+ mpg on gas alone.
So does the KLR.

Still with all those factors figgered in, I don't get why we can't pull 80-100 mpg
at ordinary steady cruise. Same questions and no answers here, Planbro.

This is my son, with whom I am well pleased." ----God
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post #8 of 13 Old 04-27-2012, 09:07 AM
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Kinda fat here too! (as long as we are being honest)
That sail of a fender on the 1st generations probly are not working in our favor either.
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post #9 of 13 Old 04-27-2012, 09:57 AM
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There are many contributing factors to this issue.

1) Aerodynamics, as said above, are terrible on a motorcycle. A good example would be a naked bike or cruiser, they usually see an improvement in mpgs with an after market windscreen.
2) Displacement and performance. The amount of power that is gotten from these tiny engines is crazy. Look at a 600cc sports bike. 120 hp out of that thing! that is 200 hp per liter (find a car that does that without turbocharging). This is why many 600cc sport bikes actually have worse mpg ratings than 1000cc versions.
3) technology is typically light years behind on motorcycles. We still have carb bikes! cars have direct injection gasoline.
4) Gearing - bikes are not geared like cars. If they had a "highway only" gear like most new cars have then we would see a bump in mpgs. Some new 4 cylinder cars have a top gear that spins less than 2000rpm at 60 mph. My diesel does 1600 rpm at 60 and the new audi a4 with 8 speed auto does 1500 rpm at 60 mph
5) Riders - most people do not ride their bikes like they drive their cars. Quicker accelerations, higher revving shifts, higher speeds, less highway driving, trying to keep up with their buddies on faster bikes, etc.
6) competition - most motorcycles already get twice the mpgs as the average car, so manufacturers have no incentive to concentrate on improving mpgs because consumers are already getting that benefit. I think as car mpgs improve, motorcycles will start in the same direction. Look at the new honda coming out NC700X or whatever its called, concentration on mpgs and commuting.

Here is a great example for technology. The BMW G650 Sertao gets 65 plus mpgs with a 650cc thumper that has 42 whp. It is heavier than the klr and has the same size wheels, but it has fuel injection and a modern motor (relatively speaking).
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post #10 of 13 Old 04-27-2012, 10:12 AM
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i'm skinny and it doesnt help, so dont bother cutting out cheeseburgers. i would expect that large bore motors to have less frictional losses per displacement measurement than small bore motors. ie a small piston creates relatively less power and relatively more friction than a large piston? i dunno, i just made that up. i know my more aerodynamic zx 11 gets much crappier mpg than the klr, but then again it does 90km/h in first gear

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