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Old 05-14-2008, 02:41 PM   #65 (permalink)
Duffman
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Quote:
Originally Posted by monroe74 View Post
I understand why the last 10 degrees would have a small effect. But I don't understand why the effect would be considered zero, or negative. In other words, I don't know why 80% would be considered preferable to 100%, if one is trying to minimize pumping losses and optimize BSFC.
Not zero and definately not negative but too small to matter. Pulling numbers out of my ass here but if you go from 100 CFM at 80 degrees and 102 at 90 degrees you have had a 2% increase in airflow but at the same time your A/F goes from 14.7 to 13.5 it has become 8.9% richer. 1.02x1.089= 11% more fuel. This jives with what you are telling us, but you have only maximised airflow by 2% which is really negligible and overall your FE will be negative becuase you are using 11% more fuel.

Thats why I put more value in the A/F ratio, the fuel injected may infact be very close to linear with pedal position but the airflow wont be throughout the whole range.

Last edited by Duffman; 05-14-2008 at 02:46 PM..
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