Anti-reversion cones are a device you put into your
head pipes, near the cylinder head, to discourage
reversion (i.e. a positive pressure wave in the pipe
that interferes with cylinder fill if it arrives
during overlap). Some are bell shaped like pictured
above and others are a pure cone shape.
At various times I've tested these things (both
styles) on exhaust systems that both showed and
didn't show evidence of reversion. The results have
always basically been about the same ...
They always seem to either cause a small loss over a
wide range, or on occassion I'll see a small loss at
only higher rpm's.
My guess is they'd be more effective on a system
where the pipe was oversized for the motor size and
target rpm. I'll continue to test these as I get
time and if I get a result on a particular setup
where they show a real advantage I'll report back.
In the meantime, it's not high on my list of
worthwhile performance mods.
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