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  1. #1

    Join Date
    Apr 2008
    Plainfield, IL

    Bigger intecooler pipes

    Hey guys. I was thinking about upgrading from 2.5" pipes to 2.75" pipes. Does anyone feel that could loose performance or would it only gain?

    I would think it would allow more flow to be right at the throttle body. But at the same time I feel that it would take more cfm, hence bigger pipes, to get to full boost.

  2. #2
    ABSOF*CKINLUTELY enjoisht's Avatar
    Join Date
    Mar 2010
    talk to Craigo..... He did this and gained 1-2mph top end if im not mistaken... the mor volume the better

  3. #3
    Moderator Snoman's Avatar
    Join Date
    Apr 2006
    South Chicagoland
    Youll definatly see better accerlation..Top end???Dont think 2 MPH is warnted by only going a 1/4 in..I could be wrong..We will see after i get Missys ski to RPM back out and install them..

  4. #4
    home of the dislexic fingers breon's Avatar
    Join Date
    Aug 2007
    port st lucie fl
    for every gain there is a loss will gain flow but loose throddle want to keep the vol of air a small as possible between the charger and the valves for the most the larger the intercooler pipes .the less throddle response you will have ..but i also run 2.75..but i also have a smaller intake plenum

  5. #5
    Orlando Shark's Avatar
    Join Date
    Mar 2009
    Orlando, FL
    I run them and they are great, can't talk about the 2.5''s since I've never ran them.

  6. #6
    deansta's Avatar
    Join Date
    Jan 2009
    I'm sure bumble bee Gprxp runs 3.5inch pipe .. I could be wrong it might even be 4 inch..,

  7. #7
    Richieb's Avatar
    Join Date
    Oct 2008
    Sydney, Australia.
    I changed the piping on mine for the same reason.

    When calculated out, the amount of air dramatically increased, BUT..!!, theres no point in exceeding the output diameter of the intercooler, or velocity of the air as it exits causes all sorts of flow problems.

    Best thing is to keep the diameter of ALL the piping from charger to TB all the same.

    The only exception is slightly smaller diameter from the cooler to the TB, as air volume will effectively decrease, so you need to maintain velocity, never, ever larger.

    One hell of a fun bit of engineering math to get right for all occasions..(impossible almost)!!

    Best way is the same all across the board... and too large, ie 3in would start to get the air resonating etc up and down at certain conditions, reduce charge velocity compared with the TB opening, and more..!!, and as per usual, will hinder, rather than help.

  8. #8
    Swedish Viking Craigo's Avatar
    Join Date
    Jun 2008
    Quote Originally Posted by Speed_Freak_039A View Post
    Hey guys. I was thinking about upgrading from 2.5" pipes to 2.75" pipes.
    I gained accelleration and .9 MPH top speed when I installed a 2.75" pipe from the SC to the IC in my Stage II setup. I used a 2.5" pipe from the IC to the TB, because the TB is 2.25" anyway.

    I believe I found gains with this setup for a couple of reasons.

    1) The 2.75" pipe fits around the outside of the SC outlet (and not abutting the SC outlet) allowing less resistance.

    2) The 2.75" pipe allows you to use up nearly the entire 3" diameter going into the IC - allowing more volume of air to be cooled sooner.

    3) The radius of the 2.75" bend is much more gradual than the 2.5" radius - allowing less resistance to the IC.

    Try it. I bet you'll find a gain in top speed and accelleration - I did.

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