after market airflow meters

[Ron Schroeder]

At 02:01 PM 3/22/01 EST, you wrote:
>Ron wrote:
>
>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).
>
>Hello Ron,
>
>    Have you ever seen any published empirical data that verifies this 
>concept ?  Unless there is substantial error in MAP sensor readings, it does 
>not prove out in my experience. Where does the linear hp/inHg assumption
come 
>from ? The error may be in the assumption 30 Hg = 0.  What happens to your 
>theory when VE exceeds 100% ? 
>
>Paul Saltwick

Hi Paul,

This is based only on restriction.  If the fueling is off, changing the A/F
ratio without changing the restriction could possably improve (or reduce)
power by 10% or so.  I have seen this published in various places in the past.

Its actually a linear hp/psia relationship (first order, neglecting
internal friction etc....etc...). 

Changing VE (like changing cam overlap or intake length) would change the
relationship but if VE was over 100% and remained the same then the
relationship would hold.  

I am sure that it is a change in A/F ratio rather than change of
restriction that makes most of the improvement (if any) with an aftermarket
MAP.

Sometimes it is like "Our new MEGABLASTER Ignition system (with new plugs)
will put out 15% more power than your origional ignition system (with worn
out plugs)".

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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