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Exhaust design and anti-reversion

Discussion in 'Normally Aspirated Forum' started by RobT, Jun 4, 2011.

  1. RobT

    RobT Full throttle trip

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    Been reading around exhaust design recently and come across some interesting info about anti-reversion - that is elements of the exhaust manifold design that stop exhaust gas going back into the cylinder when the engine is in its induction stroke.

    Some of these 'devices' are simply a step in the exhaust tract - often the manifold flange being slightly bigger by approx 1mm than the exhaust port

    [​IMG]

    http://www.team-integra.net/forum/14-performance/57159-jdm-type-r-header-vs-dc-jdm-header.html

    Sometimes however anti-reversion cones are used in the head end of the primary pipe

    [​IMG]

    [​IMG]

    and sometimes people go even further and fit these devices

    [​IMG]

    [​IMG]

    [​IMG]

    Do they work? seem to

    http://www.team-integra.net/forum/14-performance/57178-anti-reversion-headers.html
     
  2. RobT

    RobT Full throttle trip

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    http://bugattimanifolds.com/types-of-exhaust-manifolds

    Explains why modern touring car-types use 4-2-1 design manifolds, and not 4-1s as you would expect following theory that a 4-1 is the optimum design for a full on race manifold

    [​IMG]

    also a bit on anti-reversion at the end
     
    #2 RobT, Jun 4, 2011
    Last edited: Jun 4, 2011
  3. RobT

    RobT Full throttle trip

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  4. RobT

    RobT Full throttle trip

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  5. m0rk

    m0rk sarcasm comes free
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    That makes sense. Is there room on yours to modify and add these in?
     
  6. RobT

    RobT Full throttle trip

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    Probaby yes.
     
  7. Slimy

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    Here's a question for you, with a 4-2-1 manifold what makes up the -2- pairings? Is it simply cylinders 1+2 and 3+4? Or is there some other better combination?

    I'd hazard a guess that having cylinders with opposing exhaust strokes would work better, so with a 1-3-4-2 engine sequence would 1+4 and 2+3 be the optimum?

    I can't really see how that BTCC exhaust is laid out, then again I don't know the firing order either.
     
  8. RobT

    RobT Full throttle trip

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    The vw mani above is 1-4 and 2-3 pairing so that opposite cycle phase cylinders are paired. This is so that the negative pressure pulse from exhaust stroke on one cyl acts to draw air into the cyl for the intake stroke of its pair
     

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