914 air pressure measurements, The results are in! |
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914 air pressure measurements, The results are in! |
bondo |
Jun 22 2004, 10:05 PM
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#1
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Practicing my perpendicular parking Group: Members Posts: 4,277 Joined: 19-April 03 From: Los Osos, CA Member No.: 587 Region Association: Central California |
With the help of my lovely wife, I have made the air pressure measurements on my 914 at speed. The reference point was the ashtray in the dash. The ends of both hoses were buried in the center of 2" blocks of open cell foam to prevent air movement from affecting the pressure readings. I realize the reference point is not going to be at exactly zero, but as a reference it will show pressure diffrences between different parts of the car. The windows were rolled up, and the targa top was on. Here are the numbers, in kilopascals:
at 45 MPH front center of front bumper: 0.21 middle top of front trunk lid: 0.03 inside front of front wheel well: 0.00 middle top of roll bar: -0.03 middle of rear window: -0.03 inside engine compartment (coasting at idle): -0.01 inside rear wheel well: 0.02 at 65 MPH front center of front bumper: 0.44 middle top of front trunk lid: 0.02 inside front of front wheel well: 0.01 middle top of roll bar: -0.05 middle of rear window: -0.04 inside engine compartment (coasting at idle): -0.03 inside rear wheel well: 0.03 After our last measurement, we rolled down the driver's side window and drove at 45 MPH to see what difference that made on the reference point. The rear wheel well measurement went up from 0.02 to 0.07, which means that at 45 MPH the pressure at the ashtray is 0.05 kPa lower with the driver's side window down. Whelp, there's my little numerical contribution to the 914 community. --Royce |
maf914 |
Jun 23 2004, 02:28 PM
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#2
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Not a Guru! Group: Members Posts: 3,049 Joined: 30-April 03 From: Central Florida Member No.: 632 Region Association: None |
QUOTE(bondo @ Jun 23 2004, 09:04 AM) I'm sure of the units, but the reference point is probably not at atmospheric pressure. The numbers can't tell you what pressure is at a certain place, only the difference in pressure between measured points. If you had the top off the cockpit the reference was definately not zero. If you ever ride without the top with the heater on you can easily notice the increased warm air flow at speed as the high velocity air over the cockpit creates a low pressure and pulls the heated air through. If you had the top on and windows open, it probably pressurized the cockpit. I think top on, windows up, vents closed would get you closest to 1 atmosphere or 1 bar. I like the idea of some extensive wind tunnel time. Full size with a rolling road. (IMG:style_emoticons/default/laugh.gif) |
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