Let’s start with the theory that best exhaust flow will include 2 1/2 cylinder
volume, in the exhaust pipe, before the 1st restriction…. So, for a 1 3/4″
pipe with a 1 5/8″ ID that works out to a 57″ long pipe…Before the first
baffle or restriction….Pretty damnlong pipe, right???
So, all commercial exhaust for Harleys are too short for max torque and horse
power…
But, the exhaust flow can be “tricked into good flow in a much shorter pipe.
One trick, like that used on a Thunder Header is the outside “can” at the end
of the muffler or terminus of the pipe..
The other shown here is not muchdiscussed or sold…. It is a simple reversion
dam, placed, not at the exhaust port, but very near the end or terminus of the
pipe, and INSIDE it……It can be made from one typical drag pipe baffle…
Pay attention to the direction of the baffle on installation..
Putting it in backwards with KILL power.
Putting it in will enhance torque and horsepower and make carburetor
tuning much easier…
Yeah, this crap really does work….We’ve been playing with exhaust pipes, mufflers, drag
pipes ect…..for over 40 years a few things that do work…Remember, the more volume in
the pipe/s before entering a restriction/baffle or atmosphere the smaller the exit opening
can be and the engine will still develope good power and torque…That’s why a Chevy truck
with a 350 can get good power with a single 2 inch exhaust pipe….Volume in the pipe
allows the the exhaust to cool and contract the futher it travels…
Keeping the velocity up with correct sized tubing with the proper length and reversion
dams makes for excellent flow and power from the engine.