Help me decide on a sports tourer (or rather close to it)

Discussion in 'Road Warriors' started by nemuro, Nov 8, 2012.

  1. Bugz

    Bugz Been here awhile

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    Let me rephrase; A V-motor does not have a lower efficiency grade when compared to a inline motor. A V-motor does not burn more fuel compared to an inline motor when performing the same amount of labor.

    Both engines being optimized for the job obv.
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  2. PhilB

    PhilB Long timer

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    Okay. Never mind.

    PhilB
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  3. DannyZRC

    DannyZRC Been here awhile

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    don't forget that almost part of almost an engineer.

    V engine has heavier cam drive (twice the length of camchain, more cam bearings etc).

    V engines have serious packaging constraints on intake and exhaust plumbing.

    V engines in motorcycle have relatively large imbalances in combustion forces, so bearings need to be built bigger and heavier to withstand the stresses, as well as the torsional fluctuations all through the drivetrain.

    If you just look at each combustion chamber, sure, a cylinder is a cylinder, but if you look at the practical evidence that almost every V engine is a guzzler relative to it's single-headed counterparts, the writing is on the wall as they say. Proof in the pudding. Etc etc etc.
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  4. Gryphon12

    Gryphon12 Long timer

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    I'm a civil engineer, not a mechanical engineer, but as a life-long gear-head, that sounds like a rational explanation to my original query. Thanks!

    Also, as I've said before, most riders don't care. They find a bike that they love and they ride the wheels off of it. I just have a very bad habit of overthinking just about everything. Since I can only affort one bike at a time, my bad habit keeps me busy between bikes. And I learn a lot in the process! :rofl
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  5. Bugz

    Bugz Been here awhile

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    Do not take this post as me being a smartass. Just like to comment on these V4 gass guzzlers:wink:

    It is not written on the wall as they say. You'll find a lot of Big V engines in the diesel industry (ships etc) and not because of their love for fuel :ear(Not that they are more efficient compared to a inline engine...just a lot smaller because of the V design)


    Even if a v4 would have TWICE as much friction losses it would still be a total of 4%. Whoop-di-doo. It's not even close as twice as much. It's not even close as 2% more friction losses. Friction losses pretty much only consist of the friction caused by the pistons which is the same for a V4 or I4 engine.

    Even if it was twice as much...What does your regular I4 1000cc return for fuel economy? 40ies mpg? Now according to your theory the V4 would get economy of 39.2 mpg because of being a v4.

    Pretty sure that the RCV V4 honda in MotoGP is a gas guzzler compared to the rest of the field. Man that bike is slow. Fair enough. The thing has pneumatic valves :ear

    A V engine does not have large imbalances in combustion force. When properly designed it doesn't need a balance shaft where a I4 does need one to cancel out all vibrations. Even if it had harmonic vibrations it doesn't mean it can't be fuel efficient though obv. some energy will be lost because of those vibrations.

    I'm not really sure of your point mentioned about the intake and exhaust valves. Do you have any information on this since I really can't find any about it in my books.

    Where honda get's it wrong (regarding fuel consumption....their V4 engines are a gem regarding driving charasteristics) is with the B.SFC

    If you want to know what actually determines fuel consumption regarding a ICE I'd say look at this posted a few weeks ago;

    My post from the Honda NC 700 thread. This will give you information about SFC or specific fuel consumption. As I said before, I'm dutch and I might use some words which arn't technical correct. You should be able to understand though.
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    Hello lads,

    I'm just a lurker on this forum pretty much. Really like the website but somehow I don't post very often here though I do like to get involved in this ungoing fuel consumption discussion! (I'm dutch. my dutchized english isn't THAT good).

    I'd like to start with efficiency of engines and specific fuel consumption.

    Most people do know that the thermal efficiency of a normal petrol engine is about 30% whereas the thermal efficiency of a diesel engine is about 40%. We're talking about car / motorcycle engines here. Industrial diesels found in ships and energy plants can go up to 50% currently.

    What most people do not know is that the efficiency of a combustion engine is far from constant. It is about as variable as it gets (variable as in running conditions, not because the stars don't allign that well on mondays). The easiest way of 'seeing' the different thermal efficiencies of an engine is by using a SPF diagram (Specific Fuel Consumption Diagram). Let's use one I found on wikipedia from a VW 3 cylinder 1.5. diesel engine found below;
    [​IMG]

    On the x-axle there is RPM and on the Y-axle there is the effective pressure of the engine. For the sake of simplicity the Y-axle can be read as a form of power output. The red lines are the working borders of the engine. It will nut run above those conditions.

    SPC (Specific Fuel Consumption) is how much fuel you need to get a certain power output. SFC is defined as SFC = r / Pe where r = gramms of fuel (weight) en Pe is effective power of the crankshaft. In other words; The higher the SFC the higher the efficiency of anengine is. In the above diagram we see that the ultimate sweet spot of 206 kilogram / kilowatthour with regards fuel consumption of this engine is at about 15 Pe and 2300 RPM. For maximum fuel efficiency one would have to create driving conditions to get this.

    The reality with modern cars and motorcycles is that it is near impossible to achieve these running conditions. Running on a 80% load with modern cars will end you up flying way above the speed limit! Our engines in cars and motorcycles are incredibly overpowered with regards what they have to do; My estimate is that most cars / motorcycles will be running on an engine load of around 25% (and that's for european cars, not the american supermarktet V6 / V8 / V12 SUV's. They will do much worse). You can see in the SFC diagram that an engine load is way below the optimum SFC. If we take an estimated 250% load of an engine at 2500 RPM (highway conditions) we can see that the SFC is 260ish. You need 260 - 206 = 54 gramms of fuel extra just because of how we design our cars / motorcycles. You don't need 150 BHP to get a car in motion. 40 HP is more that sufficient to get you op to 85 mph.

    I think the main reason for manufactures is that people don't really want these cars yet. People want a car / motorcycle that's responsive to their foot / wrist which means we want pretty low end gearings (I think most motorcycles go above 6000 RPM on the highway @ 85 mph) and want power.

    Now back to Honda's claim. I'm very willingly to believe it will achieve 60ish mpg figures under highway conditions. It's build in a way it will obtain a high engine load since it has such long gears / low maximum RPM, and I think even the NC is still quite a bit away from maximum efficiency! It's not that a Honda fireblade doesn't have a sweet spot, it's just nowhere near normal driving conditions.

    Don't get me wrong. Í do not know anything about building or constructing engines. I just have a good understanding of operating principles and efficiency regarding combustion engines. If anyone sees major flaws in what I've written feel free to correct me.

    I do not know exactly what causes the sweetspot (apart from that it obvious has to to with pressure ) and I do know that engineers can build engines to suit their operating conditions (a racecar will have a sfc sweetspot around it's maximum RPM under full load, since that's the place it will be running during a race) but engineers cannot peform miracles. You cannot build a sportbike to suit maximum economy if the engine has 180 bhp on tap.



    Some reading stuff;

    SPC on wiki; http://en.wikipedia.org/wiki/File:Brake_specific_fuel_consumption.svg

    http://autospeed.com/cms/title_Brake-Specific-Fuel-Consumption/A_110216/article.html

    http://www.heat2power.net/en__wasteheat_in_ices.php
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    Feel free to educate me. I love to get it all wrong.
    #45
  6. DannyZRC

    DannyZRC Been here awhile

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    I never said anything about valves, I said plumbing. I was referring to intake and exhaust manifold, airbox and header length tuning etc.

    Motorcycles don't (usually) have 6+ cylinders, so V2 or V4 engines are the V engines in question, and those have uneven firing, which means larger torque variations, which means heavier driveline parts, which means more parasitic losses through the drivetrain. The big V engines in ships have many cylinders, which can be arranged to have even firing, so this is a problem not shared between large and small V engines.

    I never attributed the economy difference only to the frictional losses in the engine, you are accidentally strawmanning me due to the language barrier.

    A V4 doesn't need a balance shaft, an I4 needs 2, but a balance shaft is not the cure for torque fluctuation in the output, that's handled elsewhere in the driveline and has friction penalties associated.

    A V4 GP bike can have the fueltank under the seat to make room for a complex and expensive to manufacture airbox, it can have carefully hand welded exhaust manifolds, but it's easier to package effective airbox and exhaust solutions with low manufacturing costs on an inline engine.

    There are some theoretical disadvantages which can't be overcome in a V engine, but there are many practical disadvantages which can be but aren't overcome due to cost.

    In any case it's a giant derail, I'll stop ;p
    #46
  7. Bugz

    Bugz Been here awhile

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    Don't get me wrong. I didn't mean to 'strawman'(that's the first time I've read that word lol..)

    Ok. I have to take a look at torque fluctations again then. Starting to get really curious how big these friction penalties are.
    #47
  8. sweetwater

    sweetwater Been here awhile

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    Nemuro....where'd you go? What did you pick? Tell us how it all washes out in the end...
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  9. ChangJiangMonkey

    ChangJiangMonkey SHANGHAI'D

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  10. JerryH

    JerryH Long timer

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    A motorcycle is not a car. A motorcycle is supposed to be fun, and is supposed to require a lot of skill to ride properly. Motorcycles are dangerous, there is no doubt about that. And they are not for everybody. Nor should the be. It takes a special type of person to ride a motorcycle. For the rest there are cars.

    To me a motorcycle is supposed to be a MACHINE and that means no electronics (electronics, not electrics, motor vehicles have electrics) A motorcycle is supposed to be a very basic elemental machine. For me they are an escape from the technology I have to live with the rest of the time. Still, FI would not absolutely prevent me from buying a motorcycle with it. I would avoid it if I could.

    But ABS is an entirely different matter, and I will never own or ride a motorcycle with it. To me the whole purpose of riding a motorcycle, and where all the fun comes from, is in controlling the bike. It comes form using all the skills I have learned over the past 35 years (all accident free on the street) to make the bike do what I want it to do. I will not have a computer taking over control of MY motorcycle.

    And for those who think ABS will always save them, well, not so. Many riders have gone down on ABS bikes by overbraking on slippery surfaces. ABS prevents the wheel from completely locking up, but it comes close enough to cause you to loose traction, and if you are leaned over when that happens, you are going down. So not only does ABS interfere with your control of the bike, but it also prevents a false sense of security.

    I am surprised to find so many proponents of ABS on an adventure riding forum. Riding a motorcycle at all is dangerous, adventure riding is a lot more dangerous. It's hard to accept the fact that a real adventure rider (most of whom seem to have a pretty macho attitude) would feel they need training wheels on their bike (which is what ABS is to me) Adventure riding is all about taking chances, about risking your life and safety to do something which most people and even many riders would consider crazy. Anyone willing to ride a motorcycle from Alaska to the tip of South America surely would not need or want ABS.

    The fuel system and brakes on many bikes are already controlled by computers. Hoe long will it be before everything is? What will there be for the rider to do? Where will the fun come form? Just how much are you willing to give up for safety? Life is full of risks. Risks are what makes life worth living. There is a lot of pleasure in using your skills to beat the odds. And if you ride a motorcycle at all, the odds are already stacked against you. Maybe the best safety device is to already be dead. That way you do not have to worry about getting seriously injured or killed.
    #50
  11. DAKEZ

    DAKEZ Long timer

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    Agree

    Define "a lot" It realy is not that hard.

    COMPLETE :topes A motorcycle is only as dangerous as the one piloting the motorcycle.


    Way to mow down the masses with your free flying and erroneous statement.

    More :topes I agree it is not for everyone but anyone that can remain remotely focused can safely pilot one with a little practice. Does that constitute Special?

    This does NOT jive with what is above. A motorcycle IS a machine which means it is NOT inherently dangerous. What makes a motorcycle (or any tool or machine) dangerous is the one at the controls.
    #51
  12. dddd

    dddd Been here awhile

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    You describe very well YOUR perception of it. I dont ride a bike for the thrill of danger nor to brag about skills. I ride it for travelling, go far and experience these places, roads, wheather better than in a car. Not to mention the fun to lean, carve a turn, saves on gas and slip into tiny places to avoid congestion... But you have every right to buy a challenging machine. Just dont say that tech doesn't have its place on ANY bikes.
    #52
  13. bikeseamus

    bikeseamus n00b

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    I agree that motorcycles aren't more dangerous than cars. The "jaws of life" that emergency rescue people use were NOT designed to free people trapped inside flaming motorcycles.I have been riding now for over 50 years and can say I have avoided head on collisions on four occasions and being T Boned at intersections on two occasions BECAUSE I was riding a motorcycle. Cresting hills, I always ride in the outside 12" of the road.... Once on a bridge in Kona I avoided being smashed when a car driver fell asleep as he was crossing the long bridge. I was poised to leap into the Ocean to avoid being hit... stopped on the side of the bridge, when he whizzed by and missed me by a foot or two. The other 3 times happened when the oncoming cars crested the hill inside my lane. Avoiding a head on collision would have been impossible on anything but a bike, end of subject. I was saved from 2 T Bone accidents by always riding a motorcycle with plenty of horsepower. These two potential murderers blew the red light at the intersections and would have hit me if I weren't able to power out of the potentially deadly crash. Saved by the horsepower that allowed the accelleration.
    Horsepower saved me from certain injury, end of subject.
    As for injection on a bike..... I enjoy being able to not worry about cleaning garfed up old petroswill from my carbs every Spring. Don't misunderstand me, I am an ex professional bike tech and carbs are great fun to dial in and tune. Pop them off and clean them without all that electronic stuff to buy and learn how to use.... cool. On the other hand, as I have owned injected bikes I have grown fond of the fine tuning they are now capable of delivering. Early injection systems were buggy and inconsistent, but motoevolution has taken place and the new injection systems are superb. I enjoy simplicity in my bikes, but also enjoy not breaking down in the middle of nowhere. I lived in Interior Alaska for 15 years and am speaking from that experience. Breakdowns in Interior Alaska often result in death.
    I enjoy arriving alive and on time.
    One can choose to invite the grim reaper ahead of schedule by being dangerous with ANYTHING. Give a fool a gun and he will very likely do something dangerous with it. Give that fool a book of matches and he will likely do the same. Strong drink, powerful drugs, wildly fun women... fast cars or bikes.... the list goes on and on.... If a fool has a stick he will find a way to be stupid with it. Modern bikes are fun partly because they are so powerful and handle so well.
    When in the hands of a dangerous person, they can be dangerous. They have saved my life when touring and in daily use, and are not dangerous when I am driving them, end of subject. I would thank Mr Dangerous to please stay away from me. Keep the danger in your own lane, please, and tell me how kissing that walnut tree or oncoming truck works out for you.
    #53