944 Wind Tunnel Testing
#16
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Bump for those that don't read Rennlist over the weekend.
#17
Nordschleife Master
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I was re-reading your post and I am fairly impressed that there is only 133 pounds of lift. Considering that the car weighs 3000 lbs, it maintains 95% of its contact pressure at speed. Also, the measured drag was .37 which would mean that the the turbo at .33 is really more efficient. It might actually have downforce. Do you mind if I ask how much it cost you? I'd be willing to donate some money to have a 944 turbo tested if somebody in the area would like to try.
#20
Rainman
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is this the 944?
does anyone have aero data regarding the original 924 and the later 924s with the small wing? i believe the small spoiler was added to reduce the dirty air "vortices" coming off the flat back at the end of the sloped window but would like to see data..
this is all i have (no spoiler)
does anyone have aero data regarding the original 924 and the later 924s with the small wing? i believe the small spoiler was added to reduce the dirty air "vortices" coming off the flat back at the end of the sloped window but would like to see data..
this is all i have (no spoiler)
![](http://www.sportauto.ee/porsche/prototypebuilding/924-1.jpg)
#22
Three Wheelin'
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When you have a go, please measure the heights from the ends of the side skirts of the cars to determine how high the car sits from the ground in every test. please try to make a repeatable measure that everyone can use...perhaps use the edge of the metal as measured element instead of the plastic addons of the 951.
Not everyone uses the same wheels/tires/suspension and this data is beneficial for everybody only if we have the clear height and inclination of the car body from the ground.
Perhaps you can even get some of your spent money back from some of us...
Not everyone uses the same wheels/tires/suspension and this data is beneficial for everybody only if we have the clear height and inclination of the car body from the ground.
Perhaps you can even get some of your spent money back from some of us...
![](http://imageshack.us/a/img41/7372/measurex.jpg)
#23
Three Wheelin'
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I was part of a group of Datsun Z car owners that chipped in $$ to rent one of the tunnels in SC and managed 17 runs with different configurations starting with stock. We had a small team of guys who were ready with 4 cars and different add on parts. As one run was being conducted, the rest of the team prepared for the next test, by adding parts/raising /lowering the car/ductaping seams and grill openings. It was a grueling day with lots of preplanning to ensure as little wasted time once there, as the booth was not cheap, and we had it for a full day. All the tests were pre laid out so everyone knew what to do. Everyone that chipped in $$$ got the results first, and much later on, the results were released to the public in a magazine article telling our story. It was EXTREMELY helpful in planning/building aero for my Z car.
#24
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It's awesome that you took the time to do this - and share your results.
I'd think the 85 MPH data would be more important to you than the 120 MPH data. Here's a histogram of my speed from my fastest lap at the Summit Point race last weekend - which was pretty fast at a 1:26.5 - and I was only between 115 and 120 MPH for 3% of the lap.
I'd think you'd get the most impact if you could make a meaningful change in the 75-100 MPH range - that accounts for 50% of the lap. Increase your speed here and you've done something serious to improve your lap time.
I'd think the 85 MPH data would be more important to you than the 120 MPH data. Here's a histogram of my speed from my fastest lap at the Summit Point race last weekend - which was pretty fast at a 1:26.5 - and I was only between 115 and 120 MPH for 3% of the lap.
I'd think you'd get the most impact if you could make a meaningful change in the 75-100 MPH range - that accounts for 50% of the lap. Increase your speed here and you've done something serious to improve your lap time.
#25
Rainman
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id put a big ol' air dam at the bottom of the spoiler, maybe some thick sheet rubber all the way to the ground, tape up the seams and some of the grille (in concert with good ducting) and remove the PS mirror (or both if legal)...put the same rubber as skirts on the sides and put some coroplast or fiberglass paneling over all the transmission/exhaust stuff...maybe some of those evo shark fins on/near the spoiler
maybe some rear wheel covers like a 90s caddy![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
btw the addition of the spoiler to the 924 turbo may have been slightly more significant than just 0.03 Cd - remember the 931 has the hood scoop and nose grilles as well, those could contribute to some losses. maybe the spoiler is good for 0.04
gotta say though...the wingless euro 924 is a nice looking car...
maybe some rear wheel covers like a 90s caddy
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
btw the addition of the spoiler to the 924 turbo may have been slightly more significant than just 0.03 Cd - remember the 931 has the hood scoop and nose grilles as well, those could contribute to some losses. maybe the spoiler is good for 0.04
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#28
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Nice car!
I see some possible problems with using this kind of wind tunnel to detect down force. The main thing is that the wind tunnel used has a limited volume of air. Also the wind is being pulled from behind in a limited volume space possibly creating a non normal air flow path and vortices. Also the windows are down so it can't be compared to a car with the windows rolled up.
I'm not an expert on this, these are just my first impressions since I've driven a stock 944 at 100+MPH and felt the car get sucked down.
I would think that a wind tunnel is good for detecting drag friction, but not for detecting down force.
I looked in Google quickly and others, like Ferrari, have had trouble using wind tunnels to detect down force.
I see some possible problems with using this kind of wind tunnel to detect down force. The main thing is that the wind tunnel used has a limited volume of air. Also the wind is being pulled from behind in a limited volume space possibly creating a non normal air flow path and vortices. Also the windows are down so it can't be compared to a car with the windows rolled up.
I'm not an expert on this, these are just my first impressions since I've driven a stock 944 at 100+MPH and felt the car get sucked down.
I would think that a wind tunnel is good for detecting drag friction, but not for detecting down force.
I looked in Google quickly and others, like Ferrari, have had trouble using wind tunnels to detect down force.
"The wind tunnel can reveal problems, too, admitted Scott Zellner, president and CEO of King Motorsports, the exclusive U.S. distributor for Mugen. For example, Mugen spent some $20,000 in research and development to design a rear diffuser for an S2000. But during repeated tests they found "they just couldn't make it work," Scott said. So Mugen scrapped the project."
Read more: http://www.superstreetonline.com/tec...h/viewall.html
Read more: http://www.superstreetonline.com/tec...h/viewall.html
"Ferrari president Luca di Montezemolo says the Italian squad plans to shut down its windtunnel in order to verify it is working properly.
The Italian squad suffered issues with data correlation during the 2011 season, with its car not delivering the increase in downforce that windtunnel data suggested some updates should offer."
http://www.autosport.com/news/report.php/id/102996
The Italian squad suffered issues with data correlation during the 2011 season, with its car not delivering the increase in downforce that windtunnel data suggested some updates should offer."
http://www.autosport.com/news/report.php/id/102996
#29
Three Wheelin'