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Thread: Oxygen sensor placement with H-Pipe?

  1. #1
    Lifetime Member samh_08's Avatar
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    Default Oxygen sensor placement with H-Pipe?

    How close to a H-Pipe can I be with my oxygen sensors? Currently I dont have any cats and my O2 sensors are mounted 6" past the 4 pipe header collector.

    I believe H-Pipes need to be fairly close to the collectors to work properly, but I dont want to mess with my tuning. I would think having it too close would skew the readings somehow. Anyone with first hand experience?

    Also, I have true dual 2.5" exhaust right now. How much smaller does one make the h-pipe?

  2. #2
    Senior Member
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    Quote Originally Posted by samh_08 View Post
    How close to a H-Pipe can I be with my oxygen sensors? Currently I dont have any cats and my O2 sensors are mounted 6" past the 4 pipe header collector.

    I believe H-Pipes need to be fairly close to the collectors to work properly, but I dont want to mess with my tuning. I would think having it too close would skew the readings somehow. Anyone with first hand experience?

    Also, I have true dual 2.5" exhaust right now. How much smaller does one make the h-pipe?
    Typically an H-pipe is 2/3's the diameter of the rest of the exhaust. You can get some decent low-mid rpm torque with an H-pipe.
    I read somewhere that you can take a crayon and with the exhaust hot, drag the crayon from your header collector towards the rear of the car. The point at which the wax crayon stops burning, is the point at which the H-pipe should be located. I have no personal experience with this.

    If your header collectors are 2 1/2" and your exhaust is the same diameter, the h-pipe serves as the termination point for the tuning effects of the collector, If you have a 3" collector and 2 1/2" the collector termination occurs where the 2 different diameters come together.

    peace
    Hog
    1997 rcsb stock L31 longblock, Marine Intake with 28# EV6 injectors, L35 2700 stall TC,Hooker LT's 2.007 60ft

  3. #3
    Lifetime Member Chevy366's Avatar
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    I would stay before the crossover of the H pipe, about like you are now.
    2005 1500 HD , Custom OS3 SD tune .
    2006 Trailblazer
    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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