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Walt Puryear
- 3
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I’ve been trying to understand why a carbureted engine runs richer with altitude. I understand there is not as much power since less dense air results less mass charge and that oxygen percentage is lower at higher altitudes.
Since a venturi’s drop in pressure is given generally by the simplified formula p1 – p2 = s/2 (v22 - v12) it would seem the less dense (s) air would result is less pressure drop and proportionally less fuel drawn.
Am I using the wrong formula? Is there a commensurate increase in velocity of the air due to it’s lighter weight resulting in a higher differential? Does the air/fuel ratio really not change that much and it’s just oxygen/fuel ratio?
Any insight would be appreciated.
Walt
Since a venturi’s drop in pressure is given generally by the simplified formula p1 – p2 = s/2 (v22 - v12) it would seem the less dense (s) air would result is less pressure drop and proportionally less fuel drawn.
Am I using the wrong formula? Is there a commensurate increase in velocity of the air due to it’s lighter weight resulting in a higher differential? Does the air/fuel ratio really not change that much and it’s just oxygen/fuel ratio?
Any insight would be appreciated.
Walt