RE: [Chrysler300] CARTER AFB Capacity Calcs

["Richard Barber" <c300@xxxxxxx>]

A value for the density of standard air at 60 degrees is 0.07651 lbs/cubic
foot.  
2,400 lbs/hour is 40 lbs/minute.
40 lbs/minute of standard air is 522 cubic feet per minute (cfm).  2,000
lbs/hour would be 435 cfm--both reasonable values for carburetors. We need
to think about those numbers.  At speed, an engine is easily gobbling a TON
of air each hour and that air will come into the air cleaner bearing a good
deal of solid contaminants that need to be removed by the air cleaner.
Engineers, technicians, tuners and current emission control computers need
to know the mass flow of air in lbs per hour in order to match that air flow
with the required amount of gasoline or other engine fuel.  That's why the
airflows in the engine lab are computed in lbs/hour.  Volumetric flow rates
must be adjusted for temperature and pressure. Current technology utilizes
mass air flow sensors in the inlet that are adjusted for flowing pressure
and temperature.

Carburetion is always a mix of compromises, most of which are now eliminated
by sophisticated fuel injection systems.  I have often repaired and adjusted
carburetors but have no tools or skills for the repair of fuel injection
systems other than to feed them a can of overpriced mouse milk once in a
while.  Combustion air systems that route cool air to the carb(s) and are
less restrictive can increase the mass flow of air slightly at a given RPM
due to lower temperature and higher pressure air to the carb(s).

To close this dialog, I'd emphasize that a carburetor must be matched to a
particular engine and service for best results.  Putting a bigger carburetor
on an engine than it needs will most likely result in diminished performance
and drivability.  Sort of like replacing factories with 24's.  Bling-bling
does not cut it with an engine or a suspension an d bigger is not always
better.

End of lecture.  Take out paper & pencil, number 1-10, we're going to have a
quiz.

C-300'ly
Rich Barber
Brentwood, CA
1955 Chrysler C-300 (attended a nice local car show today under a sunny sky
and temperature in the 60's--attendance low due to Good Guys show in nearby
Pleasanton)

-----Original Message-----
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of jlsavard@xxxxxxx
Sent: Saturday, November 14, 2009 10:00 AM
To: paulholm@xxxxxxxxxxxxx; Chrysler300@xxxxxxxxxxxxxxx
Subject: Re: [Chrysler300] CARTER AFB Capacity Calcs



In a message dated 11/14/2009 11:34:27 A.M. Eastern Standard Time,  
paulholm@xxxxxxxxxxxxx writes:

I also  remember reading that rating carbs by CFM is a later method AND not 
the  
one used by Chrysler to calculate the requirements for their  
specifications for 
the carbs they bought to use. I seem to recall that  they used a pounds per 
minute method.
Let me "Nitpick" a little here:  As I recall, we used "Pounds Per  Hour" in 
the carb lab, and also factored in air density, checked twice a  day.  
Seems like they ran as high as 2000-2400 #/hr, for a single 4bbl in  some
cases. 
 That's all that I remember, after all it's been half a century  since 
then.  Where have all the flowers gone?
 
Joe Savard
Lake Orion, Mi.





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