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MPG's and BMW?

My new RT gets 40 with mixed driving. Some of the points Gunderwood makes are valid, but constant temp (water cooling ) hardly made a difference on the GW. A honda civic with twice the engine gets 50% better gas mileage. We really do need to just write it off to a great hobby with old tech. Kinda like small airplanes - that engine technology hasn't changed appreciably since 1945 thanks to our friends in government making certification of new technology cost prohibitive.
 
My 6 cylinder, water cooled K1600GT makes 100 HP per liter. My 6 cylinder water cooled Porsche Carrera 4S makes 101 HP per liter. The bike gets a little less than 40 mpg and the car gets right at 19-20 mpg. What does that mean? I have no freakin' idea. I just step on it on either and put gas in 'em when they need it. Who buys these things because gas mileage is a defining characteristic?
 
Interesting thread, but for me it's based on a false premise: that modern, high performance motorcycles should also get better fuel mileage than automobiles specifically designed for high fuel economy.

First, if you want a two-wheeled conveyance with Prius-beating mileage, buy a scooter. They get 65 to 125 MPG, and have that level of performance. 1200cc modern motorcycles will light up rear tires in several gears, and easily top 125 to 150 mph. Why do bike companies build big bikes with such extreme performance? Because people want to buy them. Why to people want to buy them? To exploit and enjoy that performance - at least part of the time. Modern, highly-fuel efficient cars use incredibly advanced (and expensive) technology. Would you pay that premium on a motorcycle and accept all the compromises that would inevitable be required? I wouldn't.

Secondly, motorcycles as a rule have terrible aerodynamics - especially the popular GS-style dual-sport bikes. A GS can have more aerodynamic drag than large truck - especially outfitted with big metal paniers and a top box! And, that drag increases exponentially with speed. Take a look at this chart of drag coefficents: http://www.bgsoflex.com/airdragchart.html. Here's an example of what truly excellent aerodynamics can do for motorcycle mileage - 214mpg with a 124cc Honda: http://ecomodder.com/blog/diy-aero-fairings-honda-125cc-motorcycle-214-mpg/

As an example, my 1990 K1 - one of the lowest drag production vehicles ever built at 0.38! - will get 50+ mpg at a steady 85~90 mph, and reach nearly 150mph with 100hp. And that's with 20+ year-old fuel and engine technology. My K1200RS will get 55 mpg at a steady 70mpg - but 39mpg at a steady 100mph (DAMHIK). Let's see your Prius do that. :evil
 
I ride daily;

To work, back home is 55 miles. Nice ride. My option is F350 dually diesel @ 15mpg.. I think we live in a time where mpg performance and HP can be acheived together, with 100mpg on a 1200cc bike! Just no desire to build it...and $$$. Somebody in Nascar designed/built a carb about 30-35 years ago that got near 100mpg for a racing engine! Sorry I have no more details, just a fading memory of it:(. Either dollars or oil politics killed it dead, likely the latter. My GSA is a flying brick, I know that and my KLT1200, "much heavier" sled did much better with its fairing, so aero counts indeed. Nice all the data thrown around here, however and I still shy at the fillups, nowing I ride a gas pig! A FUN gas pig:) and my best advantage this day to huge gas prices and a world of cages doing better, whatever reasons. Maybe a cold fusion bike will come of age:). I'm running out of years...Just imagine! Randy:thumb
 
Performance and economy don't have to be mutually exclusive. Of course, efficient small m/cycles and efficient small cars will always get better MPG than efficient large cars and efficient large m/cycles.

Today's cars can blow the doors off of yesterday's cars while getting way better MPG. (My sports car has a top speed of 198 mph in 5th gear -- 6th gear is for lower RPMs and higher MPG, and it certainly helps because I get 28 mpg highway with 505 hp.)

M/cycle manufacturers can do the same, but they're not working on it very hard. They could do more to improve MPG without adding much expense and still have as much performance and HP as ever.

Wouldn't we all like an RT with more HP and 8 to 10 MPG better economy? That's about a 20% improvement ... and I believe it can be done without noticeably raising the price.
 
In high school, I had a '72 Chevelle SS big block, 4-speed ride that got a couple of miles to the gallon and would melt the tires off it in the first three gears. My '07 C4S is just about as fast but gets 19 city, and high 20's on the interstate. And yeah, some kids never grow up.
 
Are you saying that it can't be measured?

Unless you're recording the mileage under set conditions and covering the surfaces/roads, it will be exceeding difficult to reliably measure the mileage difference arising from 114k Btu pure gasoline and 110.2k Btu 10% ethanol blend. The energy content variation amounts to 3.3% or 1.3 mpg on a 40 mpg bike.

There is a difference, but it's small. Accordingly, you would need tightly controlled conditions to really measure any difference.
 
Interesting thread, but for me it's based on a false premise: that modern, high performance motorcycles should also get better fuel mileage than automobiles specifically designed for high fuel economy.

First, if you want a two-wheeled conveyance with Prius-beating mileage, buy a scooter. They get 65 to 125 MPG, and have that level of performance. 1200cc modern motorcycles will light up rear tires in several gears, and easily top 125 to 150 mph. Why do bike companies build big bikes with such extreme performance? Because people want to buy them. Why to people want to buy them? To exploit and enjoy that performance - at least part of the time. Modern, highly-fuel efficient cars use incredibly advanced (and expensive) technology. Would you pay that premium on a motorcycle and accept all the compromises that would inevitable be required? I wouldn't.

Secondly, motorcycles as a rule have terrible aerodynamics - especially the popular GS-style dual-sport bikes. A GS can have more aerodynamic drag than large truck - especially outfitted with big metal paniers and a top box! And, that drag increases exponentially with speed. Take a look at this chart of drag coefficents: http://www.bgsoflex.com/airdragchart.html. Here's an example of what truly excellent aerodynamics can do for motorcycle mileage - 214mpg with a 124cc Honda: http://ecomodder.com/blog/diy-aero-fairings-honda-125cc-motorcycle-214-mpg/

As an example, my 1990 K1 - one of the lowest drag production vehicles ever built at 0.38! - will get 50+ mpg at a steady 85~90 mph, and reach nearly 150mph with 100hp. And that's with 20+ year-old fuel and engine technology. My K1200RS will get 55 mpg at a steady 70mpg - but 39mpg at a steady 100mph (DAMHIK). Let's see your Prius do that. :evil

Greg,

In Sighard Hoerner's classic "Fluid Dynamic Drag", it clearly shows that the rider is the biggest impediment to good aerodynamics. By merely adding the rider, the drag of a 500cc NSU tripled. Of course, a full fairing is shown to correct all that yield a 25~30% reduction versus a bare bike with no rider.

So, yes........K1 is good.......GS is bad
 
Greg,

In Sighard Hoerner's classic "Fluid Dynamic Drag", it clearly shows that the rider is the biggest impediment to good aerodynamics. By merely adding the rider, the drag of a 500cc NSU tripled. Of course, a full fairing is shown to correct all that yield a 25~30% reduction versus a bare bike with no rider.

So, yes........K1 is good.......GS is bad

Part of the low drag on the K1 is that the body work is designed to accommodate the profile of a tucked in rider. It's not for long distance touring, but if you go chin down on the tank your helmet fits under the wind stream of the top of the tiny windshield, and your back provides a flow surface that matches up with the rear seat cowling. You can actually feel this work in the triple digits range. Pertinent to this thread is the point that the bodywork of a car does this for you all the time.
 
Pertinent to this thread is the point that the bodywork of a car does this for you all the time.

As previously noted, part of the prius design package is a relatively low drag body shape. If you want mileage and travel at any significant speed, you can't build a vehicle with the profile of a brick or worse an unfaired trail bike.

A few pages from Hoerner's text are attached. What was obvious in the 30's is still true today......
 

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My GS gets about 43 MPG. I'm not thinking that with the cylinder heads, crash bars, and side cases (not to mention me sitting upright) that the drag coefficient is all that low on this bike.

On a side note, I saw a Smart Car driver with a great sense of humor this morning - he had a large "wind up key" attached to his tailgate! :lol
 

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On a side note, I saw a Smart Car driver with a great sense of humor this morning - he had a large "wind up key" attached to his tailgate! :lol

When I was a kid, there was an Isetta in our neighbourhood with the same accessory.
 
My R100GS with windshield and sidebags gets about 45mpg when riding two-up.

Riding alone it drops about 2mpg (I know, my wife is very aerodynamic).

Riding alone with camping gear mounted it drops below 40mpg.

And then there is the 50 year old Enfield with diesel engine which goes 130mpg. And that without all the modern features like direct fuel injection. Sure top speed is just 65 mph.

I think it is about time that companies like BMW bring out motorcycles with better gas mileage. Would be nice to ride 500 miles with the stock tank.

/Guenther (jumping back into my 15mpg truck)
 
R80G/S gets from 54 mpg riding like a granny to low 40's normal riding to low 30's balls to the wall.
 
Wonder where BMW MC program came OFF the track? About a dozen cars/suvs now get better gas mileage than my Beemer cycle, which I still love:). BUT, Even the BMW X5 Turbo Diesel gets 35mpg's, I have a friend bought one and drove it cross country. 35mpg average! My current GSA1200 is at 36-38mpg's. How poor:(. Of course many smaller and even the giant KLT get a lot better, but com'on BMW, step up and make something happen again!!! That X5 sled gets almost identical as my GSA????? Bad picture in my book. Many are talking now, even VW's are on top of the world regarding this. I WANT BMWMC to step UP to the plate and make a FULL SIZE bike with the same spunk as the VWs and BMW SUVs,etc...My GSA1200 should be at least ahead of the above heavy vehicles! The smaller 650-800BMWMCs do get a lot better, but why not a 1200, if the cages are doing it???Randy

I solved the problem: Drive my X5 diesel (30mpg+ average) when its raining and nasty cold, and need to haul a lot of stuff, or run long distances in perfect comfort. I ride the R1200RT (48mpg average) when the weather is nice and fuel prices are high or need to clear my head of daily garbage.

The GS and GSA have the problem of very poor aerodynamics: square, flat boxes make great spoilers and have huge coefficients of drag that hurt gas mileage plus all the stuff hanging out in the wind even without the cases mounted. The RT has great fairings and good aerodynamics, and great mileage capability. :thumb

The F and G bikes are obviously much lighter in weight, have less horsepower and present a narrow profile to the wind, and will naturally get better gas mileage than the GS bikes.
 
Not estimated. I saw it all through Texas, and a few other states going from AZ to Tn in 2009. Using 93, I get much better fuel economy. My range is 250-300 miles not the 200 that I get on 91.

I worked in the service department at a Volkswagen dealership when E10 Ethanol blend was introduced in the US. Across the board, we averaged a 10% decrease in fuel economy, as evidenced by customer's complaints and our own observations. I normally rode a motorcycle to work at the time, and noticed a drop in mileage there too.
 
My 6 cylinder, water cooled K1600GT makes 100 HP per liter. My 6 cylinder water cooled Porsche Carrera 4S makes 101 HP per liter. The bike gets a little less than 40 mpg and the car gets right at 19-20 mpg. What does that mean? I have no freakin' idea. I just step on it on either and put gas in 'em when they need it. Who buys these things because gas mileage is a defining characteristic?

If we did buy motorcycles based primarily on mileage, we'd all be on Royal Enfields, and 250cc Hondas, Kawis, and Suzukis.
 
My K1200RS will get 55 mpg at a steady 70mpg - but 39mpg at a steady 100mph (DAMHIK). Let's see your Prius do that. :evil

To get the best mpg's out of my Prius, I try to keep it @ 60 mph to 62 mph. At those speeds I can get upper 50's, say 57 mpg. What would it do at 70? Probably 53 mpg. My best trip was home to Bar Harbor, Maine, favorable conditions, 61 mpg. What would it do @ 100 mph? Hypermilers like me won't go anywhere near 100 in a Prius because it defeats the whole purpose of the car.

My problem is that my '03 RT is only good for around 44 mpg at 65 mph and it really needs to go faster than that in sixth gear. It prefers 70 mph or higher to avoid lugging on uphill sections. As I mentioned, the newer RT's do better, closer to 50 mpg at 65 mph.

I still challenge BMW to give us a diesel touring bike. If that's not possible due to emissions, then how about an R900RT or an F800RT? And yes, mpg's do matter, especially for those of us who want to do long tours.

Harry
 
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MY RT gets the best overall MPG of any bike I've ever owned that includes my 305 Honda Super Hawk. The RT is also the largest displacement bike I've ever owned.
 
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