Date: Fri, 04 Oct 1996 13:40 +0000
From: OMJAMA@uop.com (OMJAMA)
Subject: AIR BATH

I had an chat with Martin at Autobahn Designs today about the AIR BATH
that was featured in the October issue of EC.  

The Air bath is apparently still under development. It will funnel air to a
housing that is designed to surround the P-flo type intake filter.   I thought
it might be easier to just buy a ram air system than make one.  (Although
KAMEI makes a snorkel that replaces the reflectors on A3 VW's that
looks like it would flow plenty of air, maybe there are ducts that are
available???)

I was thinking of replacing my cracked fogs (fish tanks now) with the
snorkel and routing a duct to the air box.  Has anyone had good luck with
the CATZ or PIAA  lights or do they get chewed up by road debris too.

Just for laughs I calculated what the static pressure of air streams at
different velocities would be....@70 F

0.0156 psig @30 mph   
.0626 psig@60mph   
.141psig@90mph

So you can see that at highway speeds the extra air will make a small
difference (on the order of atmospheric pressure variations).
The only trouble is you have to move enough air (about 300cfm!!!) to keep
up with engine needs otherwise the airbox pressure will drop...no effect
in that case.

Just thinking out loud..

Omar 
92 SLC
92 GTi


Date: Tue, 15 Oct 1996 00:58:46 -0400
From: Eeeeees@aol.com
Subject: Hotair

In a previous post relating to the slavish use of cone type aircleaners to
replace the stock aircleaner in watercooled VWs in general and Corrados I
suggested that the increase in inlet temperature due to inducting under-hood
air out weighed the advantage of greater air flow.  Peripheral advantages
such as a more aggressive sound and looking ⌠Cool■ were left to individual
preference. Rooting around on some the links on Jan▓s Page I came across
Bowlings Automotive Formulas
........http://devserve.cebaf.gov/~bowling/auto.html........  This site has a
bunch of ⌠equations■ that can conveniently predict automobile behavior when
various variables are plugged in. One solves for the effect of inlet
temperature given engine displacement and horsepower.  I ran VR6 numbers for
several ambient temperatures.  The results are listed below.  Note that the
results are inverted, the table assumes constant performance therefore
horsepower appears to go up with temp.


Engine   Uncorrected   Corrected     Corrected     Friction
               Air  
RPM      Horsepower    Horsepower    Torque     Horsepower        Temp
------------------------------------------------------------------------------
------------
5400        172.0                  176.2               171.4       43.2
                    70
5400        172.0                  179.3               174.4       43.2
                    80
5400        172.0                  182.9               177.9       43.2
                    90
5400        172.0                  186.9               181.8       43.2
                  100
5400        172.0                  191.7               186.4       43.2
                  110
5400        172.0                  197.3               191.9       43.2
                  120

Members of the list that have temporarily relocated the MFA temperature
sensor to the air inlet tract can tell us what a typical temperature
differential between outside ambient and underhood air is.  I lost track of
that valuable data.  Note that a 10 degree increase will account for a HP
loss roughly equal to the numbers quoted in tuners ads.  You can bet the ads
are not conservative and you can bet the hood was up for the dyno run. 

Some have suggested ducting cool air towards the cone filter.  This
suggestion ignores the true nature of the under-hood environment.  In short
it is like a hurricane under there.  The only sure thing is that while some
places are hot other places under hood are even hotter.  One of the main
functions of a front spoiler on a street vehicle is to reduce the air
pressure under the vehicle so that air passing through the radiator has some
place lower in pressure to exit.  Changing the attitude of the vehicle front
to rear even slightly can dramatically alter under hood temperature.  Because
of the above factors the safest strategy to assure cool dense induction air
is to pipe it in from the front of the car with no leaks.  The effect
illustrates why your car goes so good when you first fire it up on a cool
 morning with maybe a little fog.

Stock VW can be improved but you have to pay attention to what you want to
improve the most; it might be looks, it might be sound and it might be 0-60
but it might not be all three at once.