after market airflow meters

Ron Schroeder rjs at bnl.gov
Thu Mar 22 18:38:06 GMT 2001


At 12:37 PM 3/22/01 EST, you wrote:
>Hello Ron,
>
>    Interesting formula, could you please tell me where it came from ?  I
was 
>just looking at a few datalogs and (assuming this formula applies at peak hp 
>rpm, WOT) I get an average reading of 1.6 inHg.  This would imply that the 
>most to be gained with a different intake would be around 4.8%.  This engine 
>has a 70mm throttle on a plenum with 2 feet of 3 inch tubing to a filter.  
>Does this imply that multiple throttle bodies with much larger area and 
>velocity stacks would only gain 5% hp ?
>
>Paul Saltwick

Hi Paul,

As a first order aproximation with a constant A/F ratio and rpm is that
power is proportional to the amount of air that you are getting in the
engine.  With 30"Hg(0 psia) being no power and 0"Hg (14.7 psia) being
absolute max for a non-turbo engine a linear interpolation would be 3 1/3%
per inch.  Other factors such as tuned stacks would have some affect too
but this is the biggest factor.

With your example you are right, less than 5% (Unless you can also increase
rpm).

Ron Schroeder
WD8CDH
E. E. S.
wd8cdh at bnl.gov
rjs at bnl.gov
ron at 112motors.com
631 344-4561 Day
631 286-5677 Nite
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