Quote:
Originally Posted by aerohead
*EFI and CPU will automatically recalibrate ignition timing and mixture,which headers will tend to lean out.....
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there's a terrible assumption.
Quote:
Originally Posted by TimRogers
So, if you find that you "need" a length of 108", a length of 54" will also have good effect at your chosen RPM (and at double that RPM as well of course.) If you can make the length of the "midpipe" from the collector to the muffler that same 54", that will help to reinforce the pulses at your chosen RPM as well.
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I was going to bring this up since no one else has... it would be nice to get primary lengths to work with the initial exhaust pulse, but incredibly impractical for most situations(as has been discovered), but secondary, tertiary, etc can also have some noticeable effect, with each reflected pulse getting weaker.
going to the tertiary pulse, that's a primary length of 36", which isn't too unreasonable. you'll end up with less scavenging effect, but material cost and packaging issues would be far less of a burden. you'll also get a side benefit of having a 2nd strength pulse at 4000 and even a full strength pulse at 8000 (not that I see that being a design goal or anything). that actually should round out your powerband pretty well, since you'll also have a 4th strength pulse at 1000 and even a 5th at 500.
in reality..... look at the factory manifold, it would be somewhat difficult to make a worse design. it is in no way made to take advantage of any exhaust tricks, just simply somewhat correctly sized and made of a cheap, easily formed material.