Quote:
Originally Posted by California98Civic
No gauges. There is no formula for an reasonable estimate? This aint a race car... seems like an estimate should be good enough if I build something twice as strong as estimated need and be fine, no?
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I don't know how one would be able to come up with a formula for estimation since this will vary on every car due to shape and lift coefficient, and won't be constant on the car anyway (there might be different pressure at the outside edges of the trunk lid than the middle, for instance).
As freebeard said, you can make a cheap pressure gauge like we used to use at one of the organ building shops I worked in (but only one--the others, we used Magnahelics which are much easier to get an accurate reading from). Take a length of clear vinyl tubing, bend it into a U, zip tie it to a ruler, fill the U with some water. Keep one end in the cabin for atmospheric pressure, put the other end at a right angle to the flow in the area of interest. The difference between the height of the water in each arm of the U is your pressure differential.