vtec

Discussion in 'General VFR Discussions' started by jjake, Feb 28, 2007.

  1. jjake

    jjake New Member

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    what are the advantages of vtec
     
  2. Bubba Zanetti

    Bubba Zanetti Member

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    None that I know of...

    (Warning: The above statement is not meant to offend, damage, corrupt, or inflame the VTEC owners on this forum. It is a statement of fact and does not represent the views of VFR World and it subsidiery companies and entities. :biggrin: )

    From my understanding, Honda uses this technology in some of their cars. In a very simple statement...it was supposed to deliver more power. Does it? Who knows...it seems on all the Dyno info people have put on the site show all VFR's are very similar in HP.

    I am sure a 6th gen owner will provide the complete mechanical explanation on the VTEC. I have it but can't find it LOL!

    It's all preference my man. You'll be happy whether you buy a VFR with VTEC or not! All VFR's rock!

    BZ
     
  3. mordred

    mordred New Member

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    Emissions cheating
     
  4. VaRollOn

    VaRollOn New Member

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    its main purpose is to add complexity, cost of maintenance and extra weight. Small prices to pay for the "BOOST" at 7K:pound:.

    VTEC is for crap but the new bikes are still a well put together package of which I happily own. I'd have kept the FZ1 or bought ZX14 or something if HP was the end goal. Now, that 1098 will have me drooling for years...
     
  5. grinder

    grinder New Member

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    Ignore the above negatives they are mostly bias from what I can make out. VTEC is intended to provide more optimum air flow for the speed of the engine. Very simplistically put, at lower engine revs two valves allow better fuel mixing and at higher revs four valves allow better mixing. VTEC in theory gives better power down low while retaining power at higher revs. It is not intended to give more power at high revs. Based on the dyno curves I have seen and riding both 5th and 6th gen bikes I would say it is true that there is more power down low. However, the differences is not great and some people find the extra valves kicking in annoying. On the 05 and earlier there is a slight hesitation as they kick in which gives the feel of a more abrupt transition than there really is. 06 and later have a slightly different activation point which is supposed to reduce this effect. Personally I like the VTEC. It has never caused me any problems and a little bit of extra low down grunt is usefull in the real world. Gen 5 riders tend to think is a giant pain in the butt and hate it and also tend to be very vocal about their preference. I had the opportunity to buy either a gen 5 or gen 6 and opted for the 6 as I felt for my style of riding it was a better bike, not by much but better.
     
  6. mello dude

    mello dude Administrator

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    The only way to really tell is to put the dyno curves on top of each other. Then you will know that Honda did it for emissions only not for any power boost.

    If Honda did it right, it would be like my 6 cylinder VTEC Acura. The power is smooth from down low all the way to redline, no mid-range surge.

    MD
     
  7. RacerX

    RacerX New Member

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    what he said

    I like the tecknology not love the tecknology. I wish it had 30 to 40 more horse power and 15 more foot pounds of torque but in the real world
    I dont need it just want it
     
  8. grinder

    grinder New Member

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    The problem with the dyno curves are that there are several different ones out there. The one I put the most stock in was completed on the same dyno in the same session. Basically this shows a small improvement for the 02 over the 01 for most, but not at 7000rpm, of the range.

    Comparing the VTEC Acura to the VTEC VFR is not really reasonable. The Acura has a much more sophisticated system than the VFR and it is a true variable system while the VFR is an on/off system. Given the space and weight limits of a motorcycle I feel it is a reasonable compromise. Is it worth it? I think so but I can appreciate others feeling that it isn't.
     
  9. jjake

    jjake New Member

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    Well the reason I asked the question is I dont see 2 valves compared to 4 on the bottom end giving you more power, more gas and air equals more power, if Im not missing something, but I bought this bike for me and the mrs to ride together,so it will serve its purpose, when I want to run I take the 600rr out, later
     
  10. imnohero

    imnohero New Member

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    VTEC (or any variable valve system) is supposed to do the following:
    1) Widen the available power band, not necessarily provide more power
    2) Improve fuel economy
    3) Improve emissions

    All of these things are good and bad depending on your point of view.
     
  11. grinder

    grinder New Member

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    The reason the two valves works better at lower speed is the speed of the air flow into the cylinder. At low rpm the flow of air into the cylinder through two intake valves is slower. If you only let the air in through one intake valve the air has to speed up to compensate for the smaller area. Higher air speed mixes the fuel and air better. As the rpms increases you need more air to get more power so you open the second valve to let more air in. The speed of the air is no longer a problem as you are moving a lot more air and it automatically moves faster. In a perfect world you would vary the intake opening size to exactly match the optimum air speed. It is very complicated and expensive to do this so the VFR has a simplified system were the Honda engineers picked what they thought was the best balance. Later VFR's, 06 and on, activate at a slightly lower rpm to compensate for the dropoff in power which happened on the earlier VTEC engines. In theory it is very simple but in practice it is a very complicated equation and some compromises have been made. There are benefits but they are not large as the Gen 5 engine was pretty damn good in the first place.
     
  12. mello dude

    mello dude Administrator

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    Well grinder - you sound like an engineer (I resemble that remark) - I agree with you the theory above and -- also from your previous post if you really want to split hairs you should try running a 5th and 6th back to back on the same dyno. (Anybody do that?)

    If you look at a 6th curve its fairly obvious where the VTEC kicks in - it's about a 7 ft-lb jump within 200 RPM. The 5th is already ahead of it at 6000 Rpm and the torque curve is way smoother. By 7500 they pretty well even up.

    I spent a two week trip - trading back and forth from a 5th and 6th and the VTEC just drove me nuts. I consider the engine the heart and soul of a bike, and well I just felt the 5th motor rocks.

    Grinder - it looks like we're gonna agree to disagree on this - both bikes are excellent in thier own way - so screw it! Let's ride.

    MD
     
    Last edited: Mar 1, 2007
  13. Spike

    Spike New Member

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    However, the gen 5 won't pass the same emissions testing as the 6.0 version will. So it appears that what Honda tried to do, and I say try. Is to add all the emmissions stuff, make the gen 6 really really clean, and have about the same power as the previous version. Which, from an engineering stand point is actually pretty impressive.

    Especially if you remember back in the 70's when the stricter emmissions requirements were first rolled out on the cars, and performance generally plumetted, not dropped, just plummetted.
     
  14. grinder

    grinder New Member

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    True true. Pity were are so far apart. It would make a good discussion for a cold winter day with a few beers.
     
  15. mello dude

    mello dude Administrator

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    I'm beer up for that!:biggrin:


    MD
     
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