Downforce
12-16-2005, 12:00 PM
#3
Drifting
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Lots of truck scales leave the scales on when they're closed, so you can go through one, stop and see how much your car weighs. Then go through it again at 100mph and see how much it weighs. Subtract the difference and theres your downforce.
12-16-2005, 12:31 PM
#4
Burning Brakes
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Originally Posted by bleucamaro
Lots of truck scales leave the scales on when they're closed, so you can go through one, stop and see how much your car weighs. Then go through it again at 100mph and see how much it weighs. Subtract the difference and theres your downforce.
12-16-2005, 12:53 PM
#6
Originally Posted by Fishey
Its the best idea ever! I suggest going top speed so the diffrence is as large as possible!
DF=(T*L)/H-W
DF= Down Force
T= Time decent from peak
L= Length of jump
H= Peak height
W= Static weight of vehicle
12-16-2005, 01:21 PM
#7
Burning Brakes
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That's only correct if you don't take the frontal area and Cd in account or consider it negligible. I'm sure that it will haul a car down quicker than in a vacuum
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12-16-2005, 01:27 PM
#8
You are correct. I assumed a vaccum just to simplify the formula.
DF=((M-d)+T*L)/H-W
M= Momentum determined by static weight*speed
d= Drag determined by cd of vehicle (corrected to wind standard 3mph southwest)/.23^2.
DF=((M-d)+T*L)/H-W
M= Momentum determined by static weight*speed
d= Drag determined by cd of vehicle (corrected to wind standard 3mph southwest)/.23^2.
12-16-2005, 08:19 PM
#9
Drifting
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Option B: I saw this once in a Lincoln Mark VIII comercial.
Take your car to a long straight away, like 2/3 the way down the backstretch of your local highschool track, and setup a high jump bar so that it just hits the roof. Get a running start at it and go under the bar as fast as you can. If there's no loud 'CLANG' then the body does creat downforce. To quantify it, dangle a string from the bar and apply chalk to the roof panel just behind the windshield. When you go back, see how far from the bar the chalk on the string is. But to make sure, try the 'CLANG' method first.
Take your car to a long straight away, like 2/3 the way down the backstretch of your local highschool track, and setup a high jump bar so that it just hits the roof. Get a running start at it and go under the bar as fast as you can. If there's no loud 'CLANG' then the body does creat downforce. To quantify it, dangle a string from the bar and apply chalk to the roof panel just behind the windshield. When you go back, see how far from the bar the chalk on the string is. But to make sure, try the 'CLANG' method first.
12-16-2005, 10:11 PM
#10
Burning Brakes
I think it does make some but i do not know how much. Also i am prittysure the 951 rear valance adds some more down force. I plan to be intalling one on my N/A this winter. IT in the garage and ready to put on. I just have to find the time and a day that i will not freeze my but off while working the garage.
12-17-2005, 12:59 AM
#11
Race Director
I'd be extremely surprised if the 944 body makes any downforce.
First of all, the car (like virtually all cars) is shaped like an airfoil that makes positive lift. The air must travel faster over the top of the car than under the car (if this doesn't make sense to you, look up how an airplane wing works). Secondly, the underbody of the 944 is full of stuff to cause turbulence.
I highly doubt the 951 rear valance does squat for downforce. It does clean up the drag a bit IIRC, but that's not the same thing.
The only way to create downforce with a 944 body is to drive it off a cliff. I'll go down in a hurry.
First of all, the car (like virtually all cars) is shaped like an airfoil that makes positive lift. The air must travel faster over the top of the car than under the car (if this doesn't make sense to you, look up how an airplane wing works). Secondly, the underbody of the 944 is full of stuff to cause turbulence.
I highly doubt the 951 rear valance does squat for downforce. It does clean up the drag a bit IIRC, but that's not the same thing.
The only way to create downforce with a 944 body is to drive it off a cliff. I'll go down in a hurry.
12-17-2005, 01:33 AM
#12
Geo, I will take an opposite on that discussion about the rear valance. My '84 944 was pretty "floaty" in the rear at highway speeds until I put on one it. It makes a bigger difference than you would think and is a "must have" add for any NA, in my opinion.
Regards,
Regards,
12-17-2005, 01:58 AM
#13
Nordschleife Master
GEO, drive a 951 at 165mph (like I have) and your take on that will change.
The car gets sucked down to the ground as you accellerate. Even moreso with a front splitter.
The 951 definately has a decent amount of downforce.. it does not get floaty at higher speeds like 944n/a and chevy cavliers that I have driven around 110mph.
The car gets sucked down to the ground as you accellerate. Even moreso with a front splitter.
The 951 definately has a decent amount of downforce.. it does not get floaty at higher speeds like 944n/a and chevy cavliers that I have driven around 110mph.
12-17-2005, 02:13 AM
#15
Hitsquad Ninja
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Originally Posted by bleucamaro
Option B: I saw this once in a Lincoln Mark VIII comercial.
Take your car to a long straight away, like 2/3 the way down the backstretch of your local highschool track, and setup a high jump bar so that it just hits the roof. Get a running start at it and go under the bar as fast as you can. If there's no loud 'CLANG' then the body does creat downforce. To quantify it, dangle a string from the bar and apply chalk to the roof panel just behind the windshield. When you go back, see how far from the bar the chalk on the string is. But to make sure, try the 'CLANG' method first.
Take your car to a long straight away, like 2/3 the way down the backstretch of your local highschool track, and setup a high jump bar so that it just hits the roof. Get a running start at it and go under the bar as fast as you can. If there's no loud 'CLANG' then the body does creat downforce. To quantify it, dangle a string from the bar and apply chalk to the roof panel just behind the windshield. When you go back, see how far from the bar the chalk on the string is. But to make sure, try the 'CLANG' method first.