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techtalk:ref:engmech04r [2020/10/20 23:19] hippysmack [Measuring Engine Crankcase Vacuum] |
techtalk:ref:engmech04r [2020/10/21 03:34] (current) hippysmack [Measuring Engine Crankcase Vacuum] |
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| And so, operating at higher elevations sometimes requires higher rated vacuum pumps to attain the same vacuum you would at lower elevations. \\ | And so, operating at higher elevations sometimes requires higher rated vacuum pumps to attain the same vacuum you would at lower elevations. \\ | ||
| And likewise, operation at higher elevations affects the air/fuel mixture in the combustion chambers since air is less dense. \\ | And likewise, operation at higher elevations affects the air/fuel mixture in the combustion chambers since air is less dense. \\ | ||
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| + | However, it doesn't appear that elevation has much to do with the amount of vacuum created in the crankcase. \\ | ||
| + | A 12" pressure drop will still be a 12" pressure drop no matter if it drops from 50 or 5000 feet above sea level. \\ | ||
| + | The important number is the pressure swing. The more vacuum that is created, the farther away from atmosphere it becomes. \\ | ||
| + | The positive makeup pressure on downstroke normally brings vacuum back to near atmosphere. \\ | ||
| + | But an increase in vacuum lowers scavenging ability for the oil pump. \\ | ||
| Gauge pressure is a measurement taken from the current atmospheric pressure level (depending on current elevation above sea level). \\ | Gauge pressure is a measurement taken from the current atmospheric pressure level (depending on current elevation above sea level). \\ | ||
| When taking a vacuum measurement, you are measuring how much the air is lower than the current atmospheric pressure at your location (elevation wise). | When taking a vacuum measurement, you are measuring how much the air is lower than the current atmospheric pressure at your location (elevation wise). | ||
