GT500 heads - Page 3

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Thread: GT500 heads

  1. #31

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    Exhaust pressures historically have run much higher than intake pressures especially at initial blow down when the exhaust valve opens. That said the engine power output is simply the total amount of fuel and air that can be burnt per operating cycle. You want to optimize the intake and especially on a turbo application you have little you can do to change what happens after the exhaust valve opens.

    Newer design turbos can produce impressive boost (and therefore power) figures at lower exhaust pressures than their older siblings. These turbos may or may not spool as quickly as some of their higher pressure hot side cousins. You need to spend time with your Turbo supplier to optimize that metric for your build. That said you'll notice that rules making bodies focus on inlet side performance (boost) when attempting to normalize performance between cars with different types of superchargers. They don't do the same for the hot side design metrics — there is a reason. You've got to keep you eye on the ball and not be distracted by side shows. Other than keeping the hot side plumbing as short and hot (at the turbine) as possible along with minimizing unnecessary bends in the tubing your horsepower is intimately associated with the compressor side of the device.

    There is an argument that can be made that restrictive exhaust plumbing creates pumping losses that are paid for with horsepower that never gets to the rear tires but the real world numbers argue that the low hanging fruit, power production-wise, is on the inlet/compressor side.

    Don't try to over-science this process, you'll be much happier.


    Ed

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  3. #32

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    So Ed, what do you consider good flow numbers in that .200 to .400 lift range on a C head

  4. #33

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    Don't forget the low off the seat lift is equally important to the cylinder's filling efficiency. The Livernois flow numbers are a poster child for the low lift and also the 0.200 to 0.400 lift range. You are unlikely to find any "C" head measurably outperform them in this range and when you look at the graph in post #4 the trace that sits clearly aboven anyone else is the Livernois Stg 3 head.


    Ed

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