![]() |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
![]() |
bondo |
![]()
Post
#1
|
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 |
![]() ![]() |
lapuwali |
![]()
Post
#2
|
Not another one! ![]() ![]() ![]() ![]() Group: Benefactors Posts: 4,526 Joined: 1-March 04 From: San Mateo, CA Member No.: 1,743 ![]() ![]() |
Bondo, great data. Thanks for doing this.
I misread those numbers at first. I'm used to seeing absolute numbers in kPa from MAP sensors, but those are obviously from the reference. The converstion is 100kPa = 1bar = 14.5psi. In the data above, 0 would be "equal to atmospheric". -0.05 would mean 0.7psi below atmospheric. 0.21 is 3psi above. On the wheel well measurements, was the sensor in front of, above, or behind the tire? It's interesting that the pressure is positive there. I'm not surprised the engine compartment is negative. The negative area above it from the back window won't help airflow in, the fan will be working hard to blow air into the space below the tin, and the engine is consuming a goodly amount of air, too. Ducting air from one of the rear wheel wells to the engine intake should help power some. |
![]() ![]() |
![]() |
Lo-Fi Version | Time is now: 15th June 2024 - 09:28 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |