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Exhaust pipe diameter

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  • Exhaust pipe diameter

    I'm building a 3.4 / 3400 turbo engine[hyper-tec pistons] using an s10 blazer for a platform. I'm trying to be reasonable in my expectations of boost and hp. What would you suggest as max boost / hp for a street driven vehicle ... 2.5 or 3 " single exhaust.

  • #2
    I like to use 3" as a minimum exhaust diameter if I'm running a single tube. The more free flowing you make the exhaust the easier the turbo will spool.
    You have to keep in mind that turbines work on a pressure differential (and some thermal properties), so the lower the pressure (or restriction) after the turbo, the easier it is to get to spool, and the more HP potential you have.

    FWIW, I have ran 2.5" on my Franken60 (3.2L 660 built from varioud generations of the 660, including a gen3 top end), and 3" on both my Nissan 2.8L I6 and my turbo LX9.