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 |
SLITS |
Jun 23 2004, 03:11 PM
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#2
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
QUOTE(fiid @ Jun 23 2004, 10:20 AM) I'm not entirely sure that most of the stuff you see on rice rockets has anything to do with real aerodynamics. I'm most interested in building a venturi tray for the underside of the rear than can actually suck air through the engine, plus increase downforce. My favorite rice-aero trick is putting a f-off great wing on the back of a front wheel drive car. Great. At speed the rear wheels are welded to the floor and the driven and steering wheels are floating. Seriously smart. Was just having a little fun. 1st - it's been around a long time and that is a full spoiler on the front of the car, riding about 1/4" off the madcam. This will create negative pressure under the car, especially if combined with side skirts. It should create a situation where air is drawn through the engine intake to underneath the car. Yeh, I know it's considered ricer but we used it on the race car (without the sideskirts) 2nd - the effectiveness of this was shown by Jim Hall on the 2J Sucker car, alabeit he had a snowmobile engine drawing air too! 3rd - For the venturi effect your talking about, I would think that a square duct from the front spoiler to a splitter underneath each engine bank with the top not sealed would create a high velocity air and at discharge create a negative pressure area below the engine. Hey, they tried it with little flaps stuck to the body. Oh well, it is obvious I have no idea of what I am talking about - so I'll just shut up (yeh, right). |
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