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even fire vs odd fire

Discussion in 'The Hokey Ass Message Board' started by Tiger II, Aug 12, 2008.

  1. Tiger II
    Joined: Mar 10, 2007
    Posts: 96

    Tiger II

    So a discussion came up regarding odd and even fire. Supposedly the Viper V10 is odd fire and the Ford Triton V10 is even fire. Any of you smart folks out there explain the difference.

  2. btbsandman
    Joined: Mar 15, 2007
    Posts: 72


    Well I have the 198 V6 oddfire Baby Nailhead in my 1962 Buick. The oddfire has more "rumble" that can be felt in the car when idling at a stoplight. It has a more throaty sound from the exhaust.

    I took this from a Buick Board that describes the oddfire issue in the V6...

    "The firing interval that proved best was every 150 and 90 degrees for each crankshaft throw with a cylinder firing order of 1-6-5-4-3-2, alternating between the cylinder banks. "That was a little bit different than people were accustomed to, and if you sat in the car at idle you had a kind of little dance that you went through, so we said it had a personality of its own."

    I have no clue about the evenfire stuff....
    Joined: Jun 15, 2006
    Posts: 3,149


    Simply put the even fire engine fire in even degrees of crankcase rotation etc. The odd fire engine are uneven spaced firing events.
    Chevy and buick both made some odd fire engine over the years as well , the odd fires ran ok but were a little rough at idle.
  4. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,041

    Relic Stew
    from Wisconsin

    Kind of Depends on the angle of the V of the block. V8's are even at 90°, V6 and V12 are even at 60°. When a V6 is based on a V8 block, they are 90°, so they are odd-fire, unless the crank has the pins offset to make it even. Both the V-10's mentioned are 90° blocks, Ford uses offset crank pins, Dodge does not.

    Here is an even fire 90° V6 crank. Funky stuff going on with journal offset.

    Last edited: Aug 12, 2008
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  5. bryan6902
    Joined: May 5, 2008
    Posts: 1,137


    Chrysler/Dodge ran the 3.9L v6 which is an odd fire engine for years, actually until 2003 I think in Dakota pick-ups. Just did training for Chrysler cam in block engines and they mention nothing about odd firing engines on the new Viper 8.4L. It does have variable valve timing though, which is insanely awesome in it's simplicity. Kinda makes me angry none of us thought of it first.
  6. Since you asked about V-10's
    The Viper uses common crank pins which creates a 54 degree -90 degree firing order as that's when the pistons come up due to the common crank throws, hence ODD Fire.
    The Ford uses split crank pins that bring the pistons up every 72 degrees, hence EVEN fire.
    At least that's how I understand it.
    Last edited: Aug 12, 2008
  7. no55mad
    Joined: Dec 15, 2006
    Posts: 1,649

    from nipomo, ca

    As said above, with the Buick V6's, the odd fires had two rods on one crank journal like the V8's. The even fire V6's had a seperate crank journal for each rod.
  8. RAG66
    Joined: Jun 1, 2008
    Posts: 160


    Oh man,
    You guys on here scare the crap out of me with all the smart thinking & tech knowledge! Great stuff I didn't know I needed to know!:cool:
  9. BeatnikPirate
    Joined: May 21, 2006
    Posts: 1,414

    from Media, Pa.

    I dug up this old thread because the new "Street Rodder" mag has an artical on a 32 Ford modified with an "Indy inspired" odd-fire V6.
    It says that AJ Foyt and others used Buick and Chevy powered race cars using an odd fire arrangement to create lots of horsepower.
    The artical says that ,with the odd-fire design "groups of two cylinders are separated by 90 degrees of rotation (like in most v8 engines) with other groups separated by 150 degrees of rotation (it's 1-6-5-4-3-2 firing patern requires 720 degrees of crank rotation for all cylinders to fire)."
    I don't get it. Does this really produce more power? If so, can someone please explain how this is and how come more engines aren't set up this way? :confused: Thanks
    dogwalkin likes this.
  10. r759ca
    Joined: Dec 23, 2008
    Posts: 38

    from nor cal

    i could be wrong but seems to me all motors take 720 degrees of rotation to fire all cylinders
  11. r759ca
    Joined: Dec 23, 2008
    Posts: 38

    from nor cal

    oops edit that, that is unless they are two stroke engines
  12. rq375
    Joined: Sep 23, 2008
    Posts: 97

    from Washington

    The other issue is strength, common rod journal (odd fire) cranks are stronger
  13. cheap-n-dirty
    Joined: Jan 28, 2002
    Posts: 508


    Here is my 259 inch 1979 Buick even fire v5. it was the protype for the Indy and nascar stage 2 motors. it had 1.88 inch intakes and made 350 hoesepower on gas. it also has a dry sump oil s[​IMG]ystem. the lower end is good for over 8000 rpms.

    Attached Files:

    Last edited by a moderator: Jun 1, 2014
  14. pinery
    Joined: Aug 3, 2014
    Posts: 1


    I read a few years ago that pulsed power at the rear wheels affected characteristics of how the tires would break free. This was in the context of motorcycle racing: when in a turn accelerating and you are near the threshold of loosing traction, pulsed power smooths out the transition so you can feel a little slippage and adjust your throttle. Smooth power makes the loss of traction more sudden and compensation with the throttle might be to late. That's what was said regarding pairing up of cylinders so that they fired at the same time. Big bang engines.
    HowlerMonkey mentions it in this forum topic at PhysicsForums but I can't find the original article. The same might be true for straight line acceleration...
  15. Hnstray
    Joined: Aug 23, 2009
    Posts: 8,100

    from Quincy, IL

    This is a very old thread. However, the biggest difference I see in your references, compared to the discussion of V6, V10 engines is the frequency of power pulses. In a 2 cylinder engine, the pulses, whether spaced or paired, still have considerable degrees of crank rotation between them. On the V6, and even more so on the V10, uneven power pulses are much closer together, and therefore relatively "smoother" in applying the power pulses to the drivetrain.

    The thing that has to be kept in mind is, all common four cycle engines fire all the cylinders, whether one or sixteen, even or odd fire, within 720 degrees of crank rotation. So, the fewer cylinders, the more "pulsing"......the more cylinders....the less extreme the pulses. Also, for a given displacement, say 2 liters for example, the number of cylinders has a great deal to do with the 'ferocity' of the power pulse since the fewer the cylinders, the more displacement each has and the corresponding power per cylinder is greater and vice versa.

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