Steve,
The point of the crossover, as you may know but didn't make clear, is not
just to equalize the pulses but use one pulse to "scavenge" the next. Just
like drafting in bicycles (or NASCAR), each pulse can pull along the next
one. Knowing that, the X design has an obvious advantage over an "H": no
right hand turns. Having said that, I think you have to have a pretty
sophisticated design to take advantage of scavenging: if two pulses
arrived simultaneously in an X pipe I suspect you'd create unpleasant
turbulence. Two stroke dirt bikes have custom designed expansion chambers
in their exhaust to take advantage of scavenging, and one dent can
dramatically alter their power.
In short I think an "H" pipe is better than no crossover, and a WELL
DESIGNED "X" pipe is better than an "H" pipe. I suspect a badly designed X
could be worse than an H. I know the whole plumbing nightmare made me
decide not to bother. Either crossover makes transmission access more
challenging unless you install flanges, and in my experience every exhaust
seam is prone to leak. Interesting theory, though!
Michael
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