Bike fuel consumption - why is it so lousy?

Discussion in 'Cars, Bikes 'n AFVs' started by gobbyidiot, Oct 9, 2009.

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  1. I'm probably repeating myself, but jesus, a lot of small cars will do 60mpg + if driven carefully, and you are talking about a load of mass, rolling resistance and air resistance. A middleweight bike, with a fraction of all of these, struggles to match the car, never mind beat it.

    How hard can it be to make a 500cc bike that would do 100mpg in normal use? My guess is that bikes tend to be leisure (or part leisure) tools, and people tend to subconsciously compare the fuel consumption to a car. Plus, the manufacturers have spent nothing like the money on engine development.

    There has to be a market for something like the old Kawasaki GT550 - shaft drive and no hassle - but with much better economy.
     
  2. Well if you want to accelerate as slowly as a 60mpg car then I'm sure they could be made that way.

    Just buy a scooter!!!
     
  3. bikes don't fall under the same emmission and durabiltiy requiremnts set down by the coordinating european council. Thusly this also means they are way behind on mpg requirements. Other factors are that bikes will rev to [11-15k] well over the 5-7k rpm of car engines unless you have a lumbering vtwin - this burns a considerable amount of fuel. it's also down to gearing ratio and torque availabilty from a 'small' bike engine matted to what can only be described as a very flimsy gearbox! It's not as simple as making them more economical but changing compression ratios/valve timing etc, you'd have to completely redesign the bike engine and gearbox - costly business when nobody is screaming for it!.
     
  4. You could always try an Enfield diesel. :lol:
     
  5. A significant part of it is air resistance. Bikes are NOT very streamlined compared to a modern car and cannot reasonably be made so due, mostly, to the size and shape of the large nut that holds the handlebars to the seat.

    Add to that the fact that the bikes you are looking at are performance optimised rather than economy optimised (look at the power outputs and compare to similarly sized car engines in your econmic cars).

    There are plenty of economical bikes out there but they dont sell well. (Harleys, for example, can easily return 50MPG+) Most UK bikers go for the sports/sports tourer or supersports genre. Would you buy a Ferrari and complain about the fuel economy compared to a diesel skoda?
     
  6. Oh and I forgot to mention riding style. I dont try to make my car accelerate as-fast-as-it-can every time I pull away. My bike on the other hand.....................
     
  7. i have the same problem.
    Sooooooooooo

    I slowed down a little
    and
    change the rear sprocket to a smaller size

    has given me about 2 extra litres a day back (on my normal journey)

    Now I just need to work on been lighter
     
  8. This is exactly the reason why... If you have a bike with an efficient (in terms of power/weight ratio) engine then fuel efficiency will be low. On the other hand...

    Yonks ago I had a big beast of a 500 single that could go like shit off a shovel but drank the benzino. Can't have it both ways...

    They don't make big soft bikes that can pull a sidecar c/w wife & kids at 40 -50 mph any more cos ppl dont want them.
     
  9. My old Harley Sportster used to return 50+mpg whether I caned it or not, mates CBR1000 on the other hand used to return -30mpg if caned and over 60 mpg if ridden sedately. My GN250 was a plodder and returned around 60mpg however it was ridden, my current Z550 ltd might do 45mpg if I`m lucky but thats on open carbs and a fairly straight through pipe.
    Unfortunately with both cars and bikes, manufacturers have to do a trade off between performance and economy because customers want the best of both worlds. With modern electronic sytems it is possible to downtune an engine at the expense of performance but people would then moan about that...you can`t please all of the people all of the time. :(
     
  10. Its funny but my highly tuned Harley 1200 sportster with a modified CV carb actually gives better economy than my almost stock 1200 sportster with fuel injection. Just shows you never can tell. Overall around 50 MPG with very little difference between town and open road or variation in speed. I think the worst I ever got out of either one was 40MPG and the best around 55MPG and that is from a comparatively heavy 1200 ridden like a tw&t wherever I go. I personally do not think 50MPG is bad considering my tendency towards throttle abuse.
     
  11. Get real, if you buy a modern sports bike i.e. R6, R1 you are buying the equivalent of a top end hyper car as far as performance goes. How many mpg do you get from Ferrari etc.

    If you want economy you need to buy a boring mid engined, fully faired commuter, economy and no fun.
     
  12. Get one of these,

    [​IMG]

    85mpg.
     
  13. Its a common complaint,but yes it is entirely accurate that most bikes have abysmal MPG.The reasons are many and varied but it appears to my mind at least that the newer bikes are even worse than older bikes.


    Bikes do have a few advantages though that make up for the the crap mpg....

    1) Filtering,so even if you are burning fuel at least you are actually moving.

    2) Multi-fuel engines....oK not quite, but almost every bike will happily run on any grade of petrol whereas certain car engines get all stroppy....useful during the last fuel strikes,where I would just go to the shortest queue rather than a specific pump.

    3) Parking....Shedload easier on a bike and less time/fuel wasted doing so....the Nice council around Fleet and Aldershot even let you park on the pavements.

    4) Its a BIKE! if I wouldnt fuel economy and aerodynamic efficiency I would have bought a poxy Ford Ka....rather than my old BMW GS.
     
  14. Hehe

    As a youth I once owned an ex WD (it was that old) BSA M20... side valve, girder forks and all. It would run on paraffin but smelt like a primus stove and if the mixture lever was set to rich produced an impressive smoke screen.

    I kid you not...

    edit to say here you go
     
  15. brettarider

    brettarider On ROPs

    Don't bank on it! my lambretta does approx 100 miles to a 12ltr tank then theres the cost of a decent fully synth oil to consider at £10+ mind you it is tuned