re: Muffler Madness

[Ken <kkeith@qnet.com>]

Jim Griffin <JGriff@pobox.com>
> 
> I've noticed that on my Syncro (and as well on my 100 with V-6), that
> when I first start the car and drive a bit, the exhaust is not nearly as
> loud as when it gets going a bit down the road, until it starts to warm
> up. Then, once it is "warmed up", it sounds noticeably louder/throatier.
> 
> In other words, it is almost as if all of a sudden, the engine/exhaust
> finally "clears it throat", and starts breathing freely.
> 
> What sort of mechanical/scientific phenomenon is happening here?
> Certainly there is some rational, scientific explanation for it. How
> about it?

Jim/List,

Let's see, Maryland huh?  Are we talking in the morning, when it's cold?
My non-engineer mind would make me suspect it could be one/both of two 
things:

1.  The moisture in the exhaust upon startup (the "steam" you see coming 
    out until the engine's warmed up) is not letting the baffling
material 
    move as freely as it would when dry, so it's cannot dampen the 
    vibrations as effectively as it would after warmup.

                                  and/or

2.  The colder pipes and such have a chilling effect on the hot gasses, 
    and denser gases move slower, so the vibrations would not be as
loud.

I really don't know.  My exhaust seems to be a little bit louder upon 
startup, and then gets quieter.  But then again, that's when the idle 
slows down too! 

Or maybe that exactly what it is, the "choke" action going away after 
warmup.

Any of you smart people know why this is?  :-)

Ken