exhaust system idea

[Gary Derian]

Its a great idea.  A few years ago I designed a muffler, like a turbo
muffler, that had a butterfly in it.  When closed, the exhaust passed
through lots of perforated holes and was damped by 2 Helmholz resonators.
When open, the exhaust went right through with minimal silencing.

Mistubishi 3000's had a setup where the muffler outlet was partially
constricted at part throttle to improve silencing.

Gary Derian <gderian at oh.verio.com>

>
>I occured to me yesterday to ask a basic question about exhaust systems.
>Since it's an advantage to have staged throttle bodies (like in 4 barrel
>carbs) why not do the same for an exhaust?  I imagine such a system could
>have a HUGE pipe between the header and the muffler and then two pipes
>exiting the muffler and going out the back.  However one would have a
>butterfly valve in it and at low RPMs and low engine load it would be
>closed. However at high RPM and/or high load it would open.  This second
>tube could even bypass the muffler to reduce back presure.  OK, what am I
>missing here?  Are the gains too small to be worth it?  This system could
>be quiet most of the time and a screamer when you want/need it to be.
>
>cheers,
>james
>