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  1. #1
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    all motor exhaust size info(back pressure doesn't give you power)

    delete
    Last edited by dillon.ornelas; 21-06-2015 at 11:19 PM.

  2. #2
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    I have a 3" exhaust on my K24, it's great. When I took my car to the exhaust shop to have it made the old fogies behind the counter literally laughed in face, following that up with 'you won't get up any hills with that'... Their opinion changed though once the exhaust was finished. Lol. Old badgers.

    Pretty loud though for a daily lol
    part time potato

  3. #3
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    It's interesting that this thread comes up as I am about to arrange for a mandrel bent stainless in the coming month. It was suggested to me that a 2 1/4 would be sufficient as I will have light mods (mild cam, extractors possibly higher compression pistons). I was leaning towards a 2.5 inch and am now solidly confused... and I have done a fair bit of research!

    Oh, and in case you were wandering - I have a B20A gold top engine - the original JDM B20A made for the 2nd gen prelude
    1986 JDM DOHC B20A Gold Top Prelude: http://www.ozhonda.com/forum/showthr...-honda-prelude
    Want JDM? I can source it for you - PM for details

  4. #4
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    Lol yes keeping this high revving angina quiet will be somewhat if a mission. The exhaust guy already said that even at 2.25 it will be loud and 2.5 even more so!
    1986 JDM DOHC B20A Gold Top Prelude: http://www.ozhonda.com/forum/showthr...-honda-prelude
    Want JDM? I can source it for you - PM for details

  5. #5
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    Having no exhaust and a bigger exhaust is 2 different things.

    Also that 3" exhaust is on a 2.2L. try it on a B16 with just bolt on and you'll see why they say to large will loose LOW END POWER!!!!!!!!!

    Not to mention the crap sound you get out of a over size exhaust!

  6. #6
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    Only time a bigger exhaust will make an engine lose power in any part of the torque curve is if the header you are using does not suit your engine,the only thing it will do is make noise with a bigger than needed setup for the street.I have always found after tuning more Honda's than I care to remember that as a rule of thumb these sizes work best for street cars
    1600 to 1800cc 60 to 65mm exhausts noise levels can be controlled without killing power by restrictive mufflers
    1800 to 2000 +cc 65 to 75mm exhausts moderate noise levels and very good power levels.
    The life of a 4 stroke engine
    It sucks it squeezes it bangs it blows

  7. #7
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    Having had a K swap and falling for the you need a 3inch trap. Sure it works, but you dont need it that big. Also muffler Vs straight pipe, You do not gain power by removing a muffler, the same goes if you add 4 mufflers to the system. The japanese are firm believers in 3inch (76mm?) being too big. With my current car, it come with a 3 inch system. I drove it for a while then went to a off the shelf 70mm japanese system which i think drives nicer, far more responsive and isn't any where near as loud. So having done both ends of the spectrum (3inch straight pipe k swap car, 3inch with muffler and 70mm system), i would without a doubt choose the 70mm over all of the others. Drivability is worth more to me then internet stardom.
    BONUS ROUND
    There is still room on the bandwagon for you.

  8. #8
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    all motor exhaust size info(back pressure doesn't give you power)
    just to correct you here, a smaller exhaust doesn't create backpressure, it has a better scavengeing effect (i.e. more negative backpressure than a larger exhaust from the exhaust flowing faster)
    S P A M | W O R K S
    hehe.
    PHC


  9. #9
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    Quote Originally Posted by dillon.ornelas View Post
    how does exhaust back pressure effect power?
    It’s actually not that complicated and it’s a proven fact..

    Possible reduced power/torque not to mention potentially reducing engine longevity.

    1.
    Exhaust systems primary function is to remove exhaust gasses from the engines combustion chambers as fast as possible!
    Good systems are designed suck out gasses at the highest pressure rate possible by designing the systems to act like a vacuum based on combined heat, pipping size and bends designed for optimal air flow.

    So to get the most out of your motor she needs to breath smooth and fast and why large systems can have a negative effect on your engine's performance,
    Bigger not always better when it comes to flow characteristics

    2. Engines are designed with back pressure in mind and are designed to rev to a selected RPM’s for that motors power band that’s based on a particular back pressure rate.

    So if you change the exhaust systems size your potentially unbalancing the motors high RPM power band by changing the pressure on the exhaust side that might contribute motor longevity
    Last edited by Lukezen27; 25-08-2013 at 06:54 PM.
    161.4KW ATW Tuned By TODA
    EG5 JDM B16A SiR-II TURBO

    13.28@106.6mph 2.117 60ft On RE001

  10. #10
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    if bigger better just run a 4". Think you could get a extra 10kws

    All the dyno paper youve supplied are from bigger displacement or worked K20 putting out 155kws atws.
    Get one on a stock b16/18 and watch the power loss of a 3'' over a correct sized performance exhaust.

  11. #11
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    and you have yet to provide any form of evidence to show you are correct

  12. #12
    3 inch is good for a k series , or turboed b series. 2.5 is gud for a b18 2 inch is gud for a b16 etc
    The Internet knows this , what's the point of this thread ?

    Have you driven a street car ( or any car) without an exhaust ? No power at all.

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