backpressure

Discussion in 'Gearhead Garage' started by funkgab, Apr 24, 2014.

  1. funkgab

    funkgab Junior Member

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    someone explain backpressure to me..

    recently i installed a downpipe (eliminated the front cat) from a cali spec 1.8 liter motor.. i seemed to have lost alot of bottom end torque, but gained high end..

    the piping diameter is 2.5".. the stock piping is a sad 1 7/8 " so the exhaust goes from a 2.5 back to a 1 7/8

    i was planning to do the whole exhaust in 2.25 or 2.5 for a motor swap i'm planning to do later (2.4L)
    if i went 2.5 or 2.25 right now, would i lose even more bottom end? (leaning towards 2.25 to keep it more civil)

    also would it be better to just sell the downpipe with the cat and run stock until i swap? (since the 2.4 uses a different header/downpipe setup)
  2. Commissar Smersh

    Commissar Smersh 2020 Staff Member

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  3. mullet1

    mullet1 Junior Member

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    at least it's a good question...... so many people don't actually understand what is going on, they're just going off of badly performed expiriments from 40 years ago.

    REALLY short TL;DR would be: what you did likely decreased backpressure..... at higher engine speeds. at lower speeds, you likely caused the opposite. there is a lot more to it than this, but an engine is a long series of compromises to meet a target goal.
  4. funkgab

    funkgab Junior Member

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    well smersh, they basically just say i need portmatched and high flow everything with a shorty header... in the dsm link and the honda one says i need high flow, not back pressure
  5. Commissar Smersh

    Commissar Smersh 2020 Staff Member

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    Right. You need the best "flow" for where you want your power band.
  6. nidex

    nidex Hood Rich

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    BRO JUST FUCKIN PUT A TURBO ON THE SHIT THEN YOU AINT GOTTA WORRY BOUT NO MUHFUCKIN BACKPRESSURE.
  7. hans5849

    hans5849 Serious as a heart attack

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    Thank you for this genius statement
  8. funkgab

    funkgab Junior Member

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    i've actually considered a turbo for a while, but the california hippy smog is getting harder and harder to pass now
  9. nidex

    nidex Hood Rich

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    Can't you register the car in Nevada or some shit?!
  10. mistawiskas

    mistawiskas kik n a and takin names

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    Nope....severe consequences for not updating auto registrations in California. You only get 30 days to re-register a vehicle in both Calif and Oregon.
  11. nidex

    nidex Hood Rich

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    No, I'm saying get a mailbox in Nevada and do all your registration through Nevada. Meaning the car would never be registered in California... cheating the system.
  12. mistawiskas

    mistawiskas kik n a and takin names

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    What I'm saying, is if you're registered in another state, you'll be sporting that state's license plates. You can only get away with it for so long before you get called out on it and the consequences
    are just not worth it. California has extreme registration fees. They have built a system of cross checks to nail people who try to do exactly what you suggested in order to bleed people for
    every registration dollar they can bilk from them.
  13. Commissar Smersh

    Commissar Smersh 2020 Staff Member

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    California may have a limit on how long you can reside in state with out of state plates as well.
  14. 86mcss

    86mcss Devouring your Soul

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    6 months
  15. Commissar Smersh

    Commissar Smersh 2020 Staff Member

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    That's what I thought. However, enforcing it is probably fairly difficult.
  16. mistawiskas

    mistawiskas kik n a and takin names

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    Sooner or later those tags need to be renewed.
  17. hans5849

    hans5849 Serious as a heart attack

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    I live in IL but I have FL plates, my plates are good until October 2015 for the cost it would be to renew my plates for one year in IL.
  18. mistawiskas

    mistawiskas kik n a and takin names

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    In Oregon it costs 86 dollars to register and 45 dollars for new plates for a new car. In Washington, the same thing costs $1700 and in California well over $2000.
    Do you see why those two states are rather strict on registration?
  19. Commissar Smersh

    Commissar Smersh 2020 Staff Member

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    Source? My vehicle would cost me $121 for new plates where I moved from in SoCal according to the DMVs online fee page.
  20. mistawiskas

    mistawiskas kik n a and takin names

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    Last edited: May 14, 2014