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Re: humidity & how our cars run

To: Paul Murch <murch@atlas.chem.utah.edu>
Subject: Re: humidity & how our cars run
From: Robert Allen <boballen@sky.net>
Date: Sun, 23 Feb 1997 23:23:42 +0000
Boy Howdy!

Ain't all that school'n payin' off! Ya'll must be a real hoot in deer
camp. Boy was I off in left field. I was figurin' it was some
combination of. . . 

A) Water as a lubricant. Car slips through the air stream better. (The
Whamo Slip'n Slide Theory.)

2) The water under the tires is lifting the car off the roadway. If the
car ain't pressin' down as hard, obviously, it must weigh less. Thus
power-to-weight ratio increases (The Big Puddle, Little VW Theory.)

iii) The water droplets turn to steam. Steam wants to expand. Raises
compression while cooling and the car sounds faster. (The whistling Tea
Kettle theory.)

four) All that water swirling around grounds the dynamo. Dynamo no
longer a drag on the motor. More power to wheels. (The Raining Prince of
Darkness Theory.)

sinko) Due to the streaming water overtaking the windshield wipers and
defeating the defogger, the squrriely handling due to hydroplaning, the
strange whistling noises coming from under the bonnet, and the slowly
dimming head lights and instruments lights, the driver breaks out in a
cold sweat at onset of adrenalin high -- greatly enhanced feeling of
speed. (The Seat Bottom Pucker Factor.)

Or I could be all wet.

Bob Allen, Kansas City, '69CGT, '75TR6

Paul Murch wrote:
> 
> Ray Gibbons responded to Tom Gehring:
> 
> On Sun, 23 Feb 1997, Tom Gehring wrote:
> 
> > Partial credit to a couple of the previous  writers.  But water neither
> > displaces air nor increases oxygen content.  For a given temperature and
> > atmospheric pressure a cubic foot of air contains the same amount of
> > oxygen no matter how much water it has in it.  However, as an earlier
> 
> > Tom Gehring
> > Chemical Engineer & '65 MGB owner
> 
> Tom,
> 
> I hesitate to dispute a Chemical Engineer, but what about Dalton's Law?
> 
> Each gas in a mixture exerts a pressure according to its own
> concentration, independently of the other gases present.  That is, each
> 
> <<<<<<<<<<<Snip>>>>>>>>>>>>>>
> 
> For a fixed pressure P, the partial pressure of oxygen would be less in
> humid air than in dry air.  I contend, then, that a cubic foot of dry
> air
> contains more O2 than a cubic foot of humid air, if the pressures are
> the
> same.
> 
> Ray
> 
>    Ray Gibbons  Dept. of Molecular Physiology & Biophysics
>                 Univ. of Vermont College of Medicine, Burlington, VT
>                 gibbons@northpole.med.uvm.edu  (802) 656-8910
> 
> But what about the partial pressure of the gasoline that you are adding
> to the system?  Dry air contains about 21% oxygen, adding water vapor to
> the air will decrese the overall percentage of oxygen but
> it but will it not also lower the percentage of fuel that you are able
> to get into the air?  I think that the performance increases that are
> seen have more to do with the density of the air entering the intake.
> Lower temperature = more O2 per/liter.  There was a discussion of air
> boxes a while back for T series cars where the conventinal wisdom seems
> to be the colder the air going into the intake the better....is the
> reason for injecting water into the air cleaners more for being a swamp
> cooler effect, cool the air to make it denser?
> 
> just my 2 cents
> 
> Paul Murch
> University of Utah (5000' and low density air)
> Chemistry (Organic Ph.D. in a month)
> 66b


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