Custom VF500 exhaust w/pics

Discussion in '1st & 2nd Generation 1983-1989' started by slowbird, Nov 6, 2011.

  1. slowbird

    slowbird Member

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    Guy on VFRD made a Custom Exhaust for his VF500.

    [​IMG]
    [​IMG]
    [​IMG]


    I think it looks great...who knows how it'll flow. Will look pretty sweat if it's coated.

    What would you call this? A 4-2-1?
     
  2. invisible cities

    invisible cities New Member

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  3. matt1986vf500f

    matt1986vf500f New Member

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    Oh that looks so sweet!!
     
  4. InterFester

    InterFester New Member

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    4-2-1 or tri-y. Looks great. I'd leave it the way it is, looks trick. If it went all nasty with use I'd bead blast and paint. It'll prolly work fine.
     
  5. slowbird

    slowbird Member

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    There was a discussion on a previous VF500 exhaust thread regarding the Length of pipe needed per Cylinder to help ensure smooth flow of exhaust pulses.

    I don't think this set was made with anything like that in mind.
     
  6. InterFester

    InterFester New Member

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    A rough calculation based on a similar engine would be around 20" headpipe length before merge. This length is also based on redline rpm. It should work better than OE regardless. Collector size is less important but can also be figured out.
     
  7. invisible cities

    invisible cities New Member

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    If I could ask, what intel are you basing this on?

    From everything I have read it is pretty hard to tune these bikes and most systems fall short compared to the stock set-up.

    Also adding to the puzzle, all the 'back in the day' images I have seen of track set-up First Gen V4s show 4-2 (staggered length) exhausts.
     
  8. InterFester

    InterFester New Member

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    A member on another board who worked for Graves MotorSports at the time used their exhaust design program to calculate dimensions for my 1997 TL1000S. It's a single pin 90degree V-twin. The VF500F engine is effectively this times two.
    Redline and where you want power to be the best affects the head pipe length. Higher or peakier the shorter the headpipe. Longer will help with midrange and broaden the power and the torque curve. 10,500 is redline on a TL and my optimum headpipe length is 20" to 23". The VF500 is similar. This was also pairing one front and one rear then merging all 4 instead of pairing fronts and rears.
    Most OE exhaust is close in length and diameter but they do such a terrible job on merges and bends sometimes.
     
  9. matt1986vf500f

    matt1986vf500f New Member

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    I wonder if that guy would make more to sell?
     
  10. InterFester

    InterFester New Member

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    In real general terms, displacement will affect pipe diameter but so will shooting for higher peak power. Cam timing affects pipe length as well as shooting for peak horsepower and higher rpm range.
    A street pipe will be smaller diameter and longer versus an all out race pipe. Pairing the fronts and the rears keeps the timing more manageable from a scavenging perspective but this depends on how soon after that they all merge into one. The ol' skool race bikes may have kept them separate for this reason.
    My comments were from a street pipe perspective, largest area under torque curve for broad less peaky power delivery that improves on the OE system.
     
  11. slowbird

    slowbird Member

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    I don't think just having a simlar degree cylinder banks makes it similar. Won't Crank angles come into play as well as other factors?

    I don't think just making custom exhaust is guaranteed to gain performance on a VF500.

    Hell...even throwing cans on these bikes are known to hinder performance.

    (for the record I still think the custom made exhaust I originally posted is hella cool)
     
  12. ferrarone

    ferrarone New Member

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    This is fantastic. I love seeing new things on old 500's.
     
  13. InterFester

    InterFester New Member

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    There has been alotta discussion on this over on TLZone and TLPlanet for TL1000's. None of the systems I've ever seen for a 90 degree V, be it custom or Yoshimura, M4, what have you, have unequal length primaries before the merge except some OE systems but they do it to compensate for packaging.
    The primary length I suggested looked to be about right was based on rpm at redline, not so much engine layout or firing order.
    The race systems I've seen on most Honda V-4s are really just a pair of 2-1's, even the ones that merge right before the muffler do so just to have one muffler, they avoid the benefits of merging sooner. This may be because the odd firing order doesn't offer the advantages an even firing order does.
     
  14. invisible cities

    invisible cities New Member

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    Thanks for the post.

    For reference, a 4-2-1 exhaust system on an RC30:

    [​IMG]

    [​IMG]

    Similar to the design above (the primaries are not staggered) but the front tubes, on this RC30, are longer before they merge.

    If I could ask, is there a benefit to having longer primary tubes up front before the merge?
     
    Last edited: Nov 10, 2011
  15. InterFester

    InterFester New Member

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    I can't think of any good reason for the front bank head pipes to be longer than the rears. Maybe they make up for it in a longer tail pipe after the merge.
    That system is basically two separate exhaust systems that merge to utilize one muffler. It treats the engine like two separate engines, two parallel twins that probably fire evenly so they scavenge each other equally.

    If I build an exhaust for my 500 I'll just try to improve on the factory design by eliminating the collector box and improving all transitions to smooth flow. Also make all merges 30 degrees, this is suppose to flow and scavenge the best.

    The guy who came up with the dimensions for my TL exhaust also did a simulation for a very different motorcycle engine, a Suzuki Intruder 1400. Long stroke under square V-twin that stops making power about 4,500rpm. For largest area under torque curve, best all around street pipe, 49" long primaries before merge. Everything about this engine is opposite that of a sportbike engine.
    He ran simulations for other engines and the trend I noticed that as rpm went up, primary length went down. This isn't an exact science but a good estimate.

    Amazingly, most OE exhaust systems have very similar lengths to what he came up with but with smaller diameter pipe and wonky merges and transitions. The pipe above looks OE with it's stamped tight radius bends and bulky connections.
     
  16. JamieDaugherty

    JamieDaugherty New Member

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    FYI - You must have unequal length primaries on a V engine. Lots of math involved here so I won't bore you with that. Just keep in mind that if you make all four pipes the same length it will be, by definintion, a poorly performing system. That's the downside of any V engine configuration - the exhaust must be tuned to a certain rpm and it will lose efficiency as you move away from that point. Unless you run 4-4 or 2-2 where you never merge the front and rear together there isn't anything you can do about it.
     
  17. InterFester

    InterFester New Member

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    What V engines do this? I haven't seen this done but I definitely haven't seen everything out there. I know Ducati used to run a shorter rear headpipe to their undertail mufflers on some models but it was also a different diameter to make up for the shortness.
     
  18. JamieDaugherty

    JamieDaugherty New Member

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    All of them! As I mentioned before this is exhaust design 101, but to give you a quick overview:

    In an inline-4 engine the exhaust gas pluses exit the head at time intervals that equal 180 degrees of crankshaft rotation. These pulses are evenly spaced, think of them like cars on a freeway onramp, each with their own lane. When they merge together there will be equal space behind and in front of the cars. Now you have a V engine where the engine has a 90 degree V and 360 crank (let's say). That means one pulse comes out, then 90 degrees later (180-90) the next does, then 270 degrees (180+90), then 90, then 270, and so on. When these cars try to merge you will have too tight a space between some and too big between others.

    The only way to solve this is by giving the cars a different distance to travel - thus unequal primaries. The problem here is the timing of that (actual lengths) will depend on the flow losses and such, meaning you can only get it perfect at a single rpm. It's ok at small deviations from that rpm but progressively gets worse as you get further away. That's why V4's have such a dip in the midrage. Just look at a dyno chart and you'll see what I mean.

    I hope this helps!
     
  19. NorcalBoy

    NorcalBoy Member

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    I respectfully disagree with the midrange dip comment and that it is caused solely by the exhaust configuration. I do agree that any exhaust system is somewhat of a compromise, but the biggest contributor to the power dip in the midrange rpm's, is the jetting or FI mapping, as this is the rpm range where the regulatory agencies determine the emissions output. I have a VFR that has no dip in the midrange, with multiple dyno runs to back that claim up.

    I won't get into why I disagree with some of the other provided information, as this would be the nuclear option and there is enough fighting on the internet already.

    Here are a few words that can be added when you google Exhaust 101:

    Material Thermodynamics
    Back Pressure
    Resonance
    Reversion
    Resonance Chamber
    Scavenging
    Velocity
    Pressure Wave Dynamics
    Cylinder Head Efficiency
    Stoichiometric Ratio

    Typically, the internet isn't the best location to gather definitive information on subjects like this, the best way is to find an engineer that actually designs, builds, and tests these components for a living, and, is willing to share real world knowledge based upon extensive experience. Books on exhaust theory, design and construction are also a good method.



    .
     
  20. slowbird

    slowbird Member

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    ..
    :popcorn:
     
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