I don't understand gas mileage for motorcycles vs. cars.

[fuzzybabybunny]

Honda Fit: 117HP, 106 ft-lb @ 4800, 2604lb, 32mpg
Suzuki GSXR600: 124hp, 51 ft-lb, 412lb, 44mpg

The GSXR is about the same horsepower as the Fit, is *6 times* lighter than the Fit, but only gets 33% higher fuel mileage. Even with a 200lb person on it to make it 612lb, that's still 4.25 times lighter than the fit.

Why the huge difference? I always thought weight was a big factor in fuel economy.

 

[Eli]

Hmm...

You know, I'm actually intrigued by this too. You're right, the number disparity is huge. I don't really know how to adequately explain it.

Is it possible that a car is more aerodynamic than a motorcycle? It doesn't seem like that would make up for it though.

:hmm:

 

[Ronstang]

Can your motorcycle cruise comfortably at 70 mph with the engine spinning only 1500 rpm?

 

[EightySix Four]

The Honda Fit's motor and transmission is designed for maximum fuel economy for an acceptable level of performance.

The GSXR's motor and transmission is designed for maximum performance for an acceptable level of fuel economy.

To be more fair to the motorcycles, look at something like a Honda S2000. The combined is a mere 20mpg out of a 2700lb vehicle with a 2l motor.

Honda S2000: 237HP, 162 ft-lb @ 7800, 2765lb, 20mpg
Suzuki GSXR600: 124hp, 51 ft-lb, 412lb, 44mpg

 

[Eli]

Can your motorcycle cruise comfortably at 70 mph with the engine spinning only 1500 rpm?

Hmm. Good point.

So it would have to do with the mere 51ftlbs of torque available on the motorcycle? And of course the different design targets.

It probably does have a lot to do with engine RPM, but what about a Harley? They don't have an eleventy billion RPM redline, and get even worse mileage.. lol.

 

[Elfear]

I've often wondered about this phenomenon as well. The only thing I could come up with was aerodynamics and maybe engines that aren't as sophisticated as modern car engines?

 

[Greenman]

I don't know why it works out that way, but I do know that if I'm trashing the V-Rod, mileage goes down to around 25mpg. Piss poor for a 1250cc engine.

 

[Eli]

Hmm. The S2000 analogy is a good one.

Yep, it's all about design and gearing....

You could probably make a motorcycle get 80MPG pretty easily. But it wouldn't be fun to ride anymore.

 

[LTC8K6]

Weight has much more of an effect in stop and go driving. Cruising on the highway isn't affected much. Accelerating the extra weight a lot vs accelerating it basically once to get to cruise speed.

 

[Kelvrick]

You're comparing a sport/racing design bike to a gutless wonder minicar, that is why. Also, bikes have bad aerodynamics and past certain speeds, needs to overcome air resistance with an even smaller engine that is running high rpms.

The fit is designed around economy transportation and is on the low end of features and power. Why not compare that to the same in the bike world, ala suzuki's own gs500f. 439lb and 59mpg.

EDIT: My old 1998 yamaha yzf600r would get 55+mpg combined. My 2006 honda cbr600r would get 30+ in combined regular riding. Thrashing it brought it down substantially.

 

[Viperoni]

The bike's motor probably isn't tuned for maximum efficiency at cruising rpm's... tough when you're cruising at say 4k and can redline at 2-3 times that.

FWIW: http://answers.yahoo.com/question/index?qid=20080906204223AAxrYF8

 

[JulesMaximus]

The Honda Fit's motor and transmission is designed for maximum fuel economy for an acceptable level of performance.

The GSXR's motor and transmission is designed for maximum performance with zero thought given to fuel economy.

To be more fair to the motorcycles, look at something like a Honda S2000. The combined is a mere 20mpg out of a 2700lb vehicle with a 2l motor.

Honda S2000: 237HP, 162 ft-lb @ 7800, 2765lb, 20mpg
Suzuki GSXR600: 124hp, 51 ft-lb, 412lb, 44mpg

FTFY

 

[Throckmorton]

The gearing is set up on the bike for performance. People on Ecomodder regularly get 100mpg out of motorcycles with aerodynamic fairings and the taller gears that lower drag lets you run http://ecomodder.com/

Motorcycles aren't very aerodynamic at all. When you think about it, a bike has maybe 1/3 or 1/4 the frontal area of a car, but the coefficient of drag is much much higher.

Edit: found this http://www.r1-forum.com/forums/showthread.php?t=235116

 

[Throckmorton]

BTW there are some modded Ninjas on Ecomodder... you might want to look into that.

http://ecomodder.com/forum/showthread.php/101-5-mpg-my-2003-ninja-250-a-8686.html

 

[Throckmorton]

What about car gas mileage? A Miata gets about the same gas mileage as a 300hp Mustang or Camaro with half the power, 2/3 the weight, and less drag.

 

[the DRIZZLE]

If you look at some of the design competitions for super efficient vehicles a lot of the entries are very small displacement motorcycles with a bubble built around the rider for improved aerodynamics. I believe they have gotten over 100 mpg this way.

 

[Zap]

If you look at some of the design competitions for super efficient vehicles a lot of the entries are very small displacement motorcycles with a bubble built around the rider for improved aerodynamics. I believe they have gotten over 100 mpg this way.

Try 214MPG. Look at the links Throckmorton gave.

 

[Zenmervolt]

Honda Fit: 117HP, 106 ft-lb @ 4800, 2604lb, 32mpg
Suzuki GSXR600: 124hp, 51 ft-lb, 412lb, 44mpg

The GSXR is about the same horsepower as the Fit, is *6 times* lighter than the Fit, but only gets 33% higher fuel mileage. Even with a 200lb person on it to make it 612lb, that's still 4.25 times lighter than the fit.

Why the huge difference? I always thought weight was a big factor in fuel economy.

Weight is only a big factor in city mileage. On the highway during steady-state cruise, weight has pretty much nothing to do with anything (this is also why weight is largely irrelevant to top speed). Weight really only comes in when you have to accelerate.

Also, motorcycles are vastly less aerodynamic than cars. A typical car will have a drag coefficient between 0.3 and 0.4. Most motorcycles have a drag coefficient of nearly 1.0. Even with less frontal area, the higher Cd of a motorcycle will yield greater total drag.

Finally, engine RPM is the 800-pound gorilla in the fuel economy equation. With an automatic, the NA-market Fit spins a (relatively) leisurely 2,160 RPM at 60 mph. The GSXR600 is running at 5,250 RPM, roughly 2.4 times as fast as the engine in the Fit. The GSXR engine, while smaller, has 140% more combustion events per unit of time than the engine in the Fit; in fact, in terms of total volume of air being pumped through the engine at 60 mph, the GSXR's engine is only moving about 3.5% less than the Fit's engine.

Overall, it's actually rather amazing that the GSXR manages to do as well with fuel as it actually does.

ZV

 

[FiLeZz]

My ducati 1098 gets about 22 mpg and only weighs in at 377 dry.

 

[Zargon]

I've often wondered about this phenomenon as well. The only thing I could come up with was aerodynamics and maybe engines that aren't as sophisticated as modern car engines?

bike engines are pretty advanced, they miss out on some 'features' like VVT that cars have, due to the size and weight restrictions.

Aero is definately a factor as well


and, MPG just dont matter to the manufacturers much.

 

[roguerower]

My Triumph 675 gets 40ish on the Highway, but drops to 30s when being thrashed.

No fairings, high redline, cruises @ 5k on the highway. Sportbikes were not designed with fuel economy in mind, they are meant to go balls fast around a track.

As far as Harleys go, I don't know why they get such shitty gas mileage since all the people I see riding them do so slower than a 90 year old women barely peeping over the steering wheel in her mid-90s cadillac.

 

[QuantumPion]

The motorcycle engine can generate higher maximum power, but the average power required for cruising at maximum efficiency is much lower. E.g. the bike requires 25 HP for cruising, while the Fit requires 50 HP at the same speed.

 

[Zenmervolt]

The motorcycle engine can generate higher maximum power, but the average power required for cruising at maximum efficiency is much lower. E.g. the bike requires 25 HP for cruising, while the Fit requires 50 HP at the same speed.

Wrong. The power necessary to maintain speed is almost exclusively a factor of aerodynamics (drivetrain losses and internal engine friction also come into play, but by far the largest factor is aerodynamics). As explained earlier, even with their smaller frontal area, motorcycles actually tend to have more drag than cars due to motorcycles having absolutely atrocious coefficients of drag.

The typical car only needs at most 25-30 hp to cruise at freeway speeds on level ground.

To double speed, you need 8x the horsepower. So if a 150 hp car can hit ~120 mph, then by extension that car is only using about 19 hp when cruising on level ground at 60.

ZV

 

[hanoverphist]

i never noticed the disparity in torque/ HP for motorcycles before. is that a regular thing for mortorcycle engines? hi HP low torque?

 

[Throckmorton]

i never noticed the disparity in torque/ HP for motorcycles before. is that a regular thing for mortorcycle engines? hi HP low torque?

Yeah because they're small displacement. They make a lot of horsepower for their size by revving high.