Re: Warm vs Cool air

[Simon Favre <simon@domain.elided>]

There's no mystery here. You're also not imagining things. With an open
intake hose, any sound that burbles out of the air box will reverberate
under the hood, making the car sound "throaty". With the hose connected,
there's more hose for the sound to dissipate in, and all the remaining 
sound is out in front of the car. If you stick your ear out front by the
air intake while somebody revs the motor, you'll hear the same sound, tho
somewhat muffled.

The hot vs. cold issue is simple thermodynamics. An engine that breathes 
cool air will produce more HP than the same engine breathing hot air. 
This was the source of Fred's somewhat harsh comments that anybody who
tosses the stock air box for a "high performance" filter is kidding
themselves. If you get a high performance filter that goes INSIDE the
stock air box, you may get a slight improvement in power with better
filtration. I happen to like K&N filters.

Franco Forlini wrote:

>Upon returing home and popping the hood, I noticed that I forgot to replace
>the black flexible tubing that joins the large cigarette air filter on the
>spica air intake to the front of the car. I put the tubing back, and presto,
>the beautiful sound from the engine was gone. Now this change in sound may
>simply be a figment of my imagination, but I doubt that.

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