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Thread: MPG's and BMW?

  1. #61
    Registered User kthflieger's Avatar
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    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.
    "Wer reitet so spaet durch nacht und wind -es ist der Vater mit seinem Kind" -- Goethe
    R1200RT, F800GS
    '80 GL1100

  2. #62
    Registered User PittsDriver's Avatar
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    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?

  3. #63
    Dances With Sheep GREGFEELER's Avatar
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    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-f...cycle-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.
    Greg Feeler
    BMW MOA Director & Ambassador
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  4. #64
    Polarbear Polarbear's Avatar
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    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

  5. #65
    Norm Norms 427's Avatar
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    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.
    Now: '12 R1200RT Midnight Blue Metallic / '11 Ural Patrol 2WD ridden to Alaska / '09 KLR 650 / '05 HD Heritage Softail / '08 Harley Sportster 1200C / '85 Yamaha VMax bought new. I wasn't ready to say goodbye: www.shaunlunt.typepad.com

  6. #66
    Registered User PittsDriver's Avatar
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    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.

  7. #67
    Registered User 36654's Avatar
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    Quote Originally Posted by GregFeeler View Post
    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.
    Cave contents: 99 R11RS, 2013 Toyota Tacoma, 03 Simplicity Legacy, 97 Stihl FS75, Dewalt DW625 & DW744

  8. #68
    Registered User 36654's Avatar
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    Quote Originally Posted by GregFeeler View Post
    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-f...cycle-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.
    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
    Cave contents: 99 R11RS, 2013 Toyota Tacoma, 03 Simplicity Legacy, 97 Stihl FS75, Dewalt DW625 & DW744

  9. #69
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by 36654 View Post
    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.
    Greg Feeler
    BMW MOA Director & Ambassador
    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  10. #70
    Registered User 36654's Avatar
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    Quote Originally Posted by GregFeeler View Post
    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......
    Attached Images Attached Images
    Cave contents: 99 R11RS, 2013 Toyota Tacoma, 03 Simplicity Legacy, 97 Stihl FS75, Dewalt DW625 & DW744

  11. #71
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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!
    Attached Images Attached Images

  12. #72
    100,000+ miler 32232's Avatar
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    Quote Originally Posted by Tomcat503 View Post

    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!
    When I was a kid, there was an Isetta in our neighbourhood with the same accessory.
    Dave

    '06 Triumph Scrambler (Trans-Labrador veteran)

  13. #73
    R100GS, '89 Guenther's Avatar
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    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)

  14. #74
    On the Road
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    R80G/S gets from 54 mpg riding like a granny to low 40's normal riding to low 30's balls to the wall.

  15. #75
    2011 R1200RT ka5ysy's Avatar
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    Quote Originally Posted by Polarbear View Post
    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.

    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.
    Doug, 2011 R1200RT Polar Metallic
    MSF #127350 NAUI #36288

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