Exhaust Diameter vs engine power

Discussion in 'Engine Topic' started by jtwoods4, Mar 29, 2010.

  1. jtwoods4

    jtwoods4 Member

    Mar 19, 2010
    Atlanta, Ga.
    As the size of the exhaust system increases does the engine gain or lose power? For example, I have an L34 396 V8, what effects does a 2.5 inch vs 3.0 inch exhaust have on the engine performance/power/etc....
  2. dcozzi

    dcozzi Veteran Member

    May 1, 2002
    Phoenix, AZ
    Bigger exhaust supports more power but there is a point of diminishing return.
    You start to lose lowend torque when header primaries are too big and when the rest of the exhaust flows too freely as well. The cam profile also has a big effect on this. Lots of variables to think about.

    As a general rule, I like to think 2.5" all the way back to the rear bumper is good up to 500HP. After that, 3" can give you noticeable gains.

    Some people say 550HP is where you should start using 3". I had 523HP at the crank on a 406" motor and going from 2.5" to 3" made a difference. Sounds waaayyy cooler too.
  3. 76z28

    76z28 Veteran Member

    Jun 29, 2009
    3 inch will give you more top end
    2.5 is the way to go though
    that is what i just put on mine SOUNDS AWESOME
  4. jtwoods4

    jtwoods4 Member

    Mar 19, 2010
    Atlanta, Ga.
    I bought the car with 3 inch exhaust so I am wondering if I will get better performance with 2.5 inch, I am changing the CAM back to almost stock (little bigger) from the massive thumper that is in there now. 396 engine
  5. Simon@London

    Simon@London Veteran Member

    Feb 16, 2009
    London Ontario
    Yes it will.
  6. NYH1

    NYH1 Veteran Member

    Feb 27, 2010
    Central New Yorkistan
    Are you going to keep the 396 in the car? Or do you plan on putting a higher power 454, 496 or 502 in it sometime down the road?

    If it were me and I was going to keep the mild 396 in it, I'd go with 1 3/4" full length headers and a 2.5" full length dual exhaust system. There are a bunch of difference exhaust systems out there for gen II Camaros. I went with the Flowmaster system that uses the transverse muffler. It sounds great and has a lot more ground clearance.
  7. z28rod

    z28rod Veteran Member

    Apr 30, 2009
    hopewell junction,ny
    john lingenfelter did extensive exhaust tube dia. hp tests, he found that 2.5" tubing would support up to like 500 hp before needing 3"dia.
  8. Rick WI

    Rick WI Veteran Member

    Jul 9, 2001
    Madison, WI
    Restriction is lost power. Tailpipes especially are a power grabber. You really can't have too big of an exhaust, just poor tuning and lack of space.
  9. 5spd540

    5spd540 Veteran Member Lifetime Gold Member

    Sep 19, 2009
    Guyton, GA
    Going with a small cam 2.5 would be better than the 3.0 it has on it now.
  10. tallman1970

    tallman1970 Veteran Member Lifetime Gold Member

    Jul 31, 2000
    This is nice to know,I wasn't thinking on doing a 3".

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