Problem exhaust drone: Solution 1/4 wave, or Helmholtz resonator?

[jondee86]

I have wondered if something like this could be implemented on a 4AGE ?

Quote:A four-stroke power valve is a device fitted to four-stroke engines that
constantly adjusts the internal diameter of the exhaust system to better
suit engine speed. At low engine speeds the wave pressure within the pipe
network is low. A full oscillation of the Helmholtz resonance occurs before
the exhaust valve is closed, and to increase low-speed torque, large-
amplitude exhaust pressure waves are artificially induced.

This is achieved by partial closing of an internal butterfly valve within the
exhaust at the point where the primary pipes from the cylinders join. This
junction point essentially behaves as an artificial atmosphere. The alteration
of the pressure at this point controls the behavior of reflected waves at this
sudden increase in area discontinuity. Closing the valve increases the local
pressure, inducing the formation of larger-amplitude negative reflected
expansion waves.

A servo motor controlled by the ECU opens and shuts the valve.[1] The
valve goes from being almost fully closed at idle speed, through to fully
open at higher engine speeds. This ensures superior low to mid-range
performance, more linear power output and reduced exhaust noise levels
while the valve is in its reduced opening position.

It might even be a solution for the mid-range drone

Cheers... jondee86