rmsnoel Posted January 6, 2013 Share Posted January 6, 2013 Ive a 5efhe manifold to fit to my 4e. i dont have the downpipe 2-1 section but the exhaust guy in work was more than happy to make it up.My question us the 4efe has a few inches of secondary pipe whereas the 5efhe has almost 12-14 inches of pipe. Do any of you guys study motorsport fancy calculating primary and secondary lengths for a 4efe for mid-range performance.The size of the collector pipe - Where the exhaust pipes all converge - is also important. It doesn't matter how many cylinders the engine has, or how large it is; It all depends on airflow. From the same magazine as I got the inlet length diagram, I also have one for the exhaust. It's used the same way, but you need to find out the number of degrees your cams have between when the exhaust opens to when the inlet opens, then read up to the revs, then to the numbers on the left hand side, which give you the length of the exhaust in feet. Another example, the same 4AGE as I mentioned before, you'd want the effective exhaust length (The distance from the middle of the exhaust valve to the first muffler) to be about 3 3/4' long.With the length of the individual pipes coming from the head, a good rule-of-thumb for a 4-2-1 system is to make the 2-1 pipes (called the 'secondaries') join together at about half the distance that you've calculated in the above diagram. The 4-2 pipes (called the 'primaries) should be half that again. With a 4-1 system, make all the primary pipes half the length in the diagram. If your engine makes 200hp, then you'll need about a 2 1/4" ID pipe, and with more power you'll need a bigger ID pipe, of course. Turbo engines are a different beast, however - Bigger is (usually) better! With any turbo engine of reasonable power you'd have to think about a 3" pipe, perhaps larger ... In any case, the tip of the exhaust should exit at a point where there is a low pressure region to minimise back pressure. It's a cheap form of weak turbocharging. Quote Link to post Share on other sites
rmsnoel Posted January 6, 2013 Author Share Posted January 6, 2013 http://www.billzilla.org/exhaust.gif4efe intake opens 2' btdc exhaust opens 38'bbdc Quote Link to post Share on other sites
rmsnoel Posted January 26, 2013 Author Share Posted January 26, 2013 (edited) .. Problems posting graph Edited January 26, 2013 by rmsnoel Quote Link to post Share on other sites
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