Re: Warm vs Cool air

["Rich Wagner" <drsavage@domain.elided>]

Frank wrote:

>1- Has anyone noted the afore-mentionned change in their cars? (ie: am I
>totally crazy?)

As anybody who's ever fallen in love with an Offy will tell you, the intake
side of an engine can make a lot of noise.  Most manufacturers go to some
trouble to muffle the noise by drawing intake air from inside one of the
fenders, around a headlight bezel, or from a front end valance panel. 
They're even more careful about it when it comes to diesel engines, which
have no throttle.  Take off the air filter, and you'll hear even more
noise.  Nope, you're not crazy.


>2- Is there any drawback to drawing in warmer air from the engine bay than
>cooler air from outside?

Yes.  All of Alfa's 2 liter engines produce different amounts of power
depending upon the model year, but let's say the the engine in your car
produces 129 HP at sea level on a standard day (72 degrees F), breathing
outside air.  Now let's say we reroute the intake plumbing so that it's
breathing air from the engine compartment, and let's say that the air in
there is 110 degrees F.  Breathing that air, the engine will make about 114
HP.  So you can see that it's important for an engine to breathe the
coolest air that can be found.  Unfortunately, that often means ducting the
outside air to the engine, making more of a mess in the engine compartment,
and muffling the intake noise at the same time.


Rich Wagner
Montrose, CO
'82 GTV6 Balocco

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