I note that many people are leaving much power on the table. The ends of

the runners where they enter the plenum should have the look of a trumpet
bell. The radius should be at least two diameters of the pipe being
supplied. A sharp corner at the inlet will flow about half what a well
radiused tube will flow. Get on a flow bench and try it. If the tube
prodrudes through the wall of the plenum it should have a fully radiused

bell shape as seen on the "Twinn Induction" web site.

A fragment of pop rivet stem, a tiny piece of a stone, a chunk of

featherfill or a safety wire clipping can destroy a rotary before you can
say "what?". I would run an air filter with as much surface area as I could
install. I run a 14" X 5" K&N element. Too big for an airplane but not too
big from the power standpoint. You can't loose power by adding filter area.
If all of the runner ends are radiused the throttle body will limit engine
power and should be very large indeed. If the runners are not radiused, or
poorly radiused then that will limit engine power and the size of the
throttle body doesn't matter at all.

Lynn E. Hanover

Lynn,
There is a chap locally who produces tube flanges at right angles directly
out of a piece of tube with a nice radiased edge - I don't know how better
to explain it nor do I know how he does it but it looks like a piece of tube
with a flange with a nice radiased edge at right angles to the tube - it is
not welded but drawn out of the tube itself. Would this work Lynn or does
the tube (with the bell shaped end) have to be extended into the
other larger tube.
George (down under)

 
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