VFR power band

Discussion in 'General VFR Discussions' started by slowbird, May 21, 2013.

  1. slowbird

    slowbird Member

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    Why do the V4's of the VF & VFR models have such broad useable power bands while most other bikes seem to have either a more "top-end" peak power or "low-end" torquey-ness?

    I noticed when I was at a Dyno-day my VFR was the only bike (of the Dyno sheets I saw) that had such a nice even power band without any of the valleys and high peaks of the other bikes....even the liter SS bikes!

    It can't just be the V4 engine layout can it? Can't other bike manufacturers get the same thing working with Cams, intake runner lengths, headers etc etc.
     
  2. Y2Kviffer

    Y2Kviffer Insider

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    I noticed that with mine too. Even the dyno operator commented on the pull...
     
  3. slowbird

    slowbird Member

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    It is quite unique to our bikes.


    When I owned my old VF500 I rode my friends EX500 for a few hours.
    Even though it was much newer and in "better shape" it felt buzzy and you really needed to wind the engine out to get any power.

    Yet both bikes were considered street bikes with a modest touring ability. City bikes.
     
  4. Outboard John

    Outboard John New Member

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    And isn't it weird that a current inline 600 four can make more peak horse power than our v-fours ever could.
    One of the regular members here has a quote at the bottom of their screen (probably from a cycle journalist) that goes something like " the v-four has what inline fours don't have enough of, and v-twins have too much of". Gotta love the v-four!

    John
     
  5. slowbird

    slowbird Member

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    That's a nice quote.
     
  6. DCS

    DCS New Member

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    To answer the original question, absolutely it is the V.

    From an engineering perspective, comparing inline to V of equivalent displacement, V = more torque sooner. Horizontal opposed = maximum torque immediately available.

    V2 = massive torque with low redline. V4 = lots of torque delivered more smoothly, sooner in the band. Inline 4 = higher redline with expected development of massive HP in the upper band.

    You can overcome the low-end torque deficit of the inline 4 with displacement, leaving the end user with the optimal combined experience of grunt and peak HP. Busa, ZX12, Blackbird.

    You can also go the same route with the V (ie VFR12), delivering incredible full-band power delivery with a huge V, but you'll never be able to wind it as fast a similar sized inline, so it won't shine like the huge inlines at the top of the band.
     
  7. CandyRedRC46

    CandyRedRC46 Member

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    No that is way off base.
     
  8. DCS

    DCS New Member

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    Oh yes huh!
     
  9. ridervfr

    ridervfr Member

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    You have to rev that EX500 to make power, I enjoy riding it as much as the viffer though. Did a 600 mile trip on it with not so-much-as-a-hick-up. Its no Vee-Four though...I run the EX wide open on the highway at about 110 or so, and 1000 RPM under red line...I run the viffer 9000 rpm on the highway and it loves it!!!
     
  10. CandyRedRC46

    CandyRedRC46 Member

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    So I am sure you've got some good reasoning behind the powerband of an Aprilia RSV4 vs a CBR1000rr...
     
  11. slowbird

    slowbird Member

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    Yeah....that's one of the reasons im asking.

    I've always been under the impression the V-4 engine configuration made the nice broad powerband but I'm seeing dynos of the RSV4 and R1's and they look pretty much the same.

    If a smooth, broad powerband is attainable in any engine configuration why don't we see it as often in bikes that don't have the displacement?
     
  12. CandyRedRC46

    CandyRedRC46 Member

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    its just marketing, the v4 often gets associated with the vtwin due to their sound and feel. so broud powerband is an easy selling point of our v4 engine, even though it is really the relatively small 36mm throttle bodies, the extremely long and narrow exhaust primaries and the relatively tame 225 degrees of duration on our intake and exhaust cams that make for the flat powerband.

    powerband is just a factor of cam profile and timing, port size, bore x stroke and how much air an engine can flow versus how much air it should flow based on it's displacement, better known as volumetric efficiency.
     
  13. DCS

    DCS New Member

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    Without delving into an internet pissing match...

    An x-cylinder V engine with y-displacement will make more torque earlier in the rpm range than an x-cylinder Inline engine with y-displacement, assuming both are fueled, aspirated, and exhausted in the same manner. This assumes that "inline" implies parallel cylinders and "V" implies an angle of approx 30° between the cylinders. Ig the designers intended it, the straight engine will rev to a higher rpm range and create more HP along the way.

    If'n you don't like this, no one cares. Get a little education, and then re-evaluate your propensity for liking vs. learning.

    The actual dyno plots of various different motorcycle engines are a function of many many variables, including but not limited to length, diameter, and flow characteristics of induction pathways; efficiency and flow characteristics of fuel delivery (duty cycle vs demand across intended range of operation); consistency of fuel atomization in low vs high and laminar vs turbulent flow environments; valve port dimensions and placement relative to flow design objectives; intended compression; exhaust flow efficiency; exhaust flow harmonics and tuning; whether the exhaust system is designed for best available harmonics across a wide rpm range or optimal harmonics within a specific narrow range of intended operational rpms; drivetrain efficiency; the resolution of fueling parameters (whether the computer operates on 0.5, 1, 2 or 5 unit increments in terms of baro pressure, air temp, throttle position, rpm, etc). Etc.

    slowbird asked a question. I gave him a decent answer. Sort of a lunch-hour doodle. Not a super formal precise description of the vagaries of engine design. But accurate and well informed. You said it was way off. Wahfuh you talking about?

    For any engine, the greater the angle between neighbors in the firing sequence, the more time the crank is exposed to peak force of cylinder detonation on an axis closest to the centerline of the crank. This is an important element of engine design with respect to efficiency of power output. The extreme example is a well designed horizontally opposed engine. Think of how the rods are working on the crank in a 4 cyl HO engine, and then think about how those same rods are working on the crank in a straight 4. Then think about torque development. Think about whether the bike will walk away from a dead stop using only the clutch and no throttle. Try it on small or medium sized engines in straight, V, and HO configurations, and see what I'm talking about.

    In general terms, V engines develop more torque lower in the rpm band than straight engines. In general terms, straight engines can be rev'd higher than V engines, and therefore have a higher top end during which more HP can be developed.

    Yes, there are exceptions, especially in the form of exotic high-rev'ing V-12 race engines that scream murder non-stop. For a very short life. No one has yet designed an x-cylinder y-displacement V engine that can be routinely rev'd to the same rpm threshold as an x-cylinder y-displacement inline engine and deliver anywhere near the same lifespan.

    V's do this, straights do that. It's okay. They don't have to be the same, nor one better than the other.

    K?
     
  14. CandyRedRC46

    CandyRedRC46 Member

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    You are reading way too far in to things and having an engineering period all over this thread.
     
  15. CandyRedRC46

    CandyRedRC46 Member

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    What I find really comical, besides how worked up and upset you are getting bashing my education and what not is that there are people just like you arguing about inline sixes versus v sixes. They will fight it to the death saying that the inline six layout makes more torque than a v six of similar state of tune, displacement etc...

    I don't see the reason to insult my education, just because I have a different view on engine configuration than you. That doesn't really reflect to well on your character. I am simply stating that I believe that the powerband has less to do with the firing order and more to do with the actually tuning of said engine. If you view differently good for you.
     
  16. Thack

    Thack New Member

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    This is a very intresting thread. I have heard the argument v6 vurses I6. And I would have to say that the I6 is old school and has a long stroke vurses most v6 short stroke pluse the displacement difference. Not really apples to apples comparison.

    I would love to see bore, stroke, cam profiles, intake and exhaust all being equal how much difference engine layout makes.

    Tom H
     
  17. slowbird

    slowbird Member

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    Bhahahaha!!!

    Yes that would be nice, wouldn't it?

    So it's not so much the VFR's V-four Engine layout that creates the powerband....yet all VF's/VFR/V45's have the same power delivery.
     
  18. jethro911

    jethro911 Member

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    Can we agree to stop using the term "power band" please. It bring back memories of the jokes we would play on new technicians when we would tell them to go to the stock room and get a new power band. It was funny but silly at the same time. What are we really talking about here eh?

    I think referring to torque or HP curves is what we are talking about right? Sorry but power bands are made of rubber and are found in model airplanes. :potstir:
    Yes I know it was an expression used widely in the past to describe the breadth of the RPM range where a bike made usable power but that was then.

    It is an interesting subject though. One would wonder how such a comparison would turn out if bore and stroke were the same as well as lift and duration on the cams. Not to mention fueling, ignition, ram air effect if any and cooling of the cylinders. One thing that would never be the same is internal friction because the different configurations demand different quantities of moving parts in the valve train as well as a different bottom end.

    I always thought that the Vee twins generally made more torque as a result of longer stroke vs bore ratio but that isn't always the case anymore. They do generally carry a heavier flywheel though and I don't think that has changed. hmmmmmmm

    I just wrote a whole bunch and said nothing. For this I apologize and creep back into my man cave. :frown:
     
  19. Rollin_Again

    Rollin_Again Member

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    You guys should resume this argument when you are both drunk :chaingun:


    Rollin
     
  20. Robclo

    Robclo New Member

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    Don't feel bad, some of it actually seeped into my grey matter and lifted a little more fog. And I know now not go looking for a power band if Billy asks.
     
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