C3 Aerodynamics: Ventilation & Induction Airflow
06-22-2006, 08:36 AM
#81
Drifting
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St. Jude Donor '05-'07
Originally Posted by flynhi
I looked at opening up the false vents on the BB hood but they are in front of the radiator and, while they would release some lifting pressure at very high speed, the opening at this location would also reduce whatever ram air pressure I have forcing air into my scoop.
06-22-2006, 09:16 AM
#82
Burning Brakes
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OK, boys and girls, yesterday evening I taped 75 pieces of yarn all over my car and we went out and took photos on the highway. Interesting results, not really what I expected to see, but I also realized I do not know how to interpret them.
Unfortunately, I don't have the capacity to show photos here so I am asking for a volunteer to send me an e-mail address I can forward them to so one of you could post them. There are about 30 pictures, but I'll edit it down to a dozen or so.
Any takers?
John
Unfortunately, I don't have the capacity to show photos here so I am asking for a volunteer to send me an e-mail address I can forward them to so one of you could post them. There are about 30 pictures, but I'll edit it down to a dozen or so.
Any takers?
John
06-22-2006, 12:12 PM
#84
Originally Posted by 84rzv500r
If someone can give me a 3d solid model or even 2d slices of the Corvette body I can run simulations in FIDAP (A Computational Fluid Dynamics Program) and get some nice contour plots of pressure and vector plots of flow at whatever speed and angle of incidence to the body you like...
Where it would get a bit sticky is the underside of the car to the ground.
I Just finished building a 256 processor Simulation System...
Just a thought
Where it would get a bit sticky is the underside of the car to the ground.
I Just finished building a 256 processor Simulation System...
Just a thought
Carl Johansson
06-22-2006, 02:58 PM
#88
Here are some more..of the "Stringray"....just kidding John...
John...I created an album for these...I have not uploaded the others yet,but will do that later in case you need some more on the forum...
Rich
John...I created an album for these...I have not uploaded the others yet,but will do that later in case you need some more on the forum...
Rich
Last edited by rihwoods; 06-22-2006 at 03:00 PM.
06-22-2006, 03:20 PM
#89
I think this photo is interesting...it seems to indicate an "eddy" just in front of the side vent...the long string is out,away from the vette in turbulent air....think this is caused by the fender flair at rear of wheelwell...but the string in the side vent is being blown by air exiting the side vent.. so no vacuuming there...
Rich
Rich
Last edited by rihwoods; 06-22-2006 at 03:22 PM.
06-22-2006, 03:31 PM
#90
Le Mans Master
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St. Jude Donor '07
Look at the difference in cowl suction compared to the high rise hood. It's also amazing how hard the air pulls in the front of the wheel wells.
06-22-2006, 05:00 PM
#93
in looking at the front of the car, I'm amazed at how much air is going into or under the car - everything from the side body crease down! Even the air in front of the tire where the side extensions of an indy spoiler would be is being drawn in not pushed aside. I seem to recall reading accounts of top speed runs back in the day using plexiglass to block off the grill portion and just allow the air from underneath to cool the radiator. anyone else?
Also note how on the rocker the yarn appears to be showing air drawn under the car. How is it possible or was there a cross-wind that day? It would seem to me that if the underhood area is high pressure then shouldn't air be pushed out? Maybe not and this is why the C-3s run so hot inside the cabin.
Lastly - the rear of the car appears really turbulent with the yarn seeming to show different directions in various photos. This can't be good, at least thinking in terms of the raindrop smooth flow back together idea.
from these pics it would seem that the single best mod is an indy spoiler or even an 80-82 style nose that wraps around the tires. The nascars have the exact same thing (nose wider than body).
Sorry I can't contribute more but my c3 is a piece right now. I'm really interested in the discussion as I'm in the planning stages for "the project". ........estimated completion 2010
Also note how on the rocker the yarn appears to be showing air drawn under the car. How is it possible or was there a cross-wind that day? It would seem to me that if the underhood area is high pressure then shouldn't air be pushed out? Maybe not and this is why the C-3s run so hot inside the cabin.
Lastly - the rear of the car appears really turbulent with the yarn seeming to show different directions in various photos. This can't be good, at least thinking in terms of the raindrop smooth flow back together idea.
from these pics it would seem that the single best mod is an indy spoiler or even an 80-82 style nose that wraps around the tires. The nascars have the exact same thing (nose wider than body).
Sorry I can't contribute more but my c3 is a piece right now. I'm really interested in the discussion as I'm in the planning stages for "the project". ........estimated completion 2010
06-22-2006, 05:09 PM
#94
I've tried researching the Corvette LeMans Corvettes of 1968-1976...here is a link..pictures are small....but interesting on the early C3's there,nothing elaborate such as the 1969 Henri Greder Corvette(front air dams,etc) until Greenwood jumped in early-mid-70's
http://corvettes-lemans.mysite.wanad....uk/page4.html
http://corvettes-lemans.mysite.wanad....uk/page4.html
Last edited by rihwoods; 06-22-2006 at 05:11 PM.
06-22-2006, 06:08 PM
#95
Safety Car
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The yarn on the side vents made no sense to me untill I saw the car at rest. Both pieces of yarn are being blown or sucked straight back. I would say that these side vents are very functional. Also, just behind the front tire, in front of the vent, appears to be very dead. The yarn just sits there.
06-22-2006, 07:30 PM
#96
Racer
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Originally Posted by rihwoods
What would you like to see?
The most aerodynamic shape in the world is a raindrop... The rubber bumpers on the 74-82 (w/o a wing) give more of a "rain drop" closure to the air that the Vette just cut through. It is hard to tell from the pictures how mixed up the air is coming off of the back of the 73. I would like to see a video of both to see if there is a difference between the rubber bumpers and the chrome bumpered cars. (It would be interesting to see Pacer style C3's compared also.(78-82))
Last edited by Batsy74; 06-22-2006 at 07:37 PM.
06-22-2006, 07:43 PM
#97
Burning Brakes
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My commentary & notes...
First, I noticed a glaring error--The pic from the rear labeled "110 mph" where Wes has his arm out the window was not a 110 mph shot. It was the last one I took, so it's probably about 75 mph or so. But it was a good clean rear end shot. Oops.
My car:
-Stock body '73 coupe.
-OEM cowl induction hood with flapper removed, 14x3 open element drop base air cleaner with about 1" clearance to hood.
-Rear deck vent interior cover plates removed for cabin ventilation.
-Vapor cannister and A/C evap can still in place behind side vents.
-Radiator seals and shroud, control arm flaps all in place.
-OEM mechanical clutch fan.
-28 1/4" to top of front wheel wells, 27 7/8" to top of rears (my front is higher now because of the weight I've removed from the front end: smog & A/C crap, cast iron heads & manifold, etc.)
The strings at the top of the back end were just lazily floating around, not whipping about. The ones from the bottom of the back end were actually pretty stable, moving but not whipping about either. It seemed pretty calm back there, calmer than at the trailing edge of the top.
The cowl suction was already happening by 30 mph at least, that's when I thought to look. (I was busy doing the Queen's wave and throwing candy to all the kids as we drove across town to get to the highway
)
Atmosphere was calm, perhaps a very light breeze from north, which would be from the driver side in the 65 mph pics and from the passenger side in the 110 mph pics.
I guess these don't tell us much about pressure differentials over most of the body, just air flow. Like I said, I didn't see what I expected, and I don't really know how to interpret these pictures, but they are very interesting. Guess the next step is to tape smoke bombs with igniter wires all over it.....(but don't hold your breath for those pics!)
That's my car in the photos, but I wanted to shoot so I let my buddy Wes drive my car and I rode in Bruce's '80. I didn't want to get anybody in trouble, so I told 'em let's do some legal limit 65 mph shots and then a few 85 mph ones. When we got going I kept hollering to Bruce,"How fast?" He'd reply, "85!" When we got all done I asked again, "How fast were we going?" He says "85." I jumped in my car and Wes says,"Man we were hauling butt!" I say, "Bruce said we were only doing 85." Wes replies, "Like hell! We were up over 110 almost the whole time! Bruce's speedo only goes to 85!"
"Stringray"!
I love it, I'll wear that moniker with pride!
To be honest, I haven't really had time to study these closely yet myself. I wanted to do some open headlights & windows shots, but I figured we were pushing our luck with what we got, plus I plain forgot.
Thanks Rich for your help.
John
First, I noticed a glaring error--The pic from the rear labeled "110 mph" where Wes has his arm out the window was not a 110 mph shot. It was the last one I took, so it's probably about 75 mph or so. But it was a good clean rear end shot. Oops.
My car:
-Stock body '73 coupe.
-OEM cowl induction hood with flapper removed, 14x3 open element drop base air cleaner with about 1" clearance to hood.
-Rear deck vent interior cover plates removed for cabin ventilation.
-Vapor cannister and A/C evap can still in place behind side vents.
-Radiator seals and shroud, control arm flaps all in place.
-OEM mechanical clutch fan.
-28 1/4" to top of front wheel wells, 27 7/8" to top of rears (my front is higher now because of the weight I've removed from the front end: smog & A/C crap, cast iron heads & manifold, etc.)
The strings at the top of the back end were just lazily floating around, not whipping about. The ones from the bottom of the back end were actually pretty stable, moving but not whipping about either. It seemed pretty calm back there, calmer than at the trailing edge of the top.
The cowl suction was already happening by 30 mph at least, that's when I thought to look. (I was busy doing the Queen's wave and throwing candy to all the kids as we drove across town to get to the highway
)Atmosphere was calm, perhaps a very light breeze from north, which would be from the driver side in the 65 mph pics and from the passenger side in the 110 mph pics.
I guess these don't tell us much about pressure differentials over most of the body, just air flow. Like I said, I didn't see what I expected, and I don't really know how to interpret these pictures, but they are very interesting. Guess the next step is to tape smoke bombs with igniter wires all over it.....(but don't hold your breath for those pics!)
That's my car in the photos, but I wanted to shoot so I let my buddy Wes drive my car and I rode in Bruce's '80. I didn't want to get anybody in trouble, so I told 'em let's do some legal limit 65 mph shots and then a few 85 mph ones. When we got going I kept hollering to Bruce,"How fast?" He'd reply, "85!" When we got all done I asked again, "How fast were we going?" He says "85." I jumped in my car and Wes says,"Man we were hauling butt!" I say, "Bruce said we were only doing 85." Wes replies, "Like hell! We were up over 110 almost the whole time! Bruce's speedo only goes to 85!"
"Stringray"!
I love it, I'll wear that moniker with pride! To be honest, I haven't really had time to study these closely yet myself. I wanted to do some open headlights & windows shots, but I figured we were pushing our luck with what we got, plus I plain forgot.
Thanks Rich for your help.
John
Last edited by JPhil; 06-22-2006 at 07:51 PM.
06-22-2006, 09:39 PM
#98
Drifting
Originally Posted by Carl Johansson
What exactly would you need to do this? just a toy model of a specific car? The reason I ask is that we are running a C-3 at Bonneville - trying to get over 200 mph. a good look at the results could really help us!
Carl Johansson
Carl Johansson
A reasonably accurate set of 2d "slices of the car, essentially a set of ordered pairs (x,y) that make up the outline of the car if you sliced through it with a big bandsaw...
I think I could raster to vector convert this from a gif or jpeg of the outlines.
or MUCH better the same set of points in x,y,z that describe the 3d surface of the car.
or a solid model of the car done any solid modeling package like ProE, Unigraphics, or SolidWorks.
OT but related
I'm getting some motorcycle cases Laser CMM'd or Scanned into this form sor that I can CNC a new set of engine cases from billet to mount TZ250 cylinders on it... Cost ~$2500 CAD
06-22-2006, 09:42 PM
#99
Originally Posted by Batsy74
The most aerodynamic shape in the world is a raindrop... The rubber bumpers on the 74-82 (w/o a wing) give more of a "rain drop" closure to the air that the Vette just cut through. It is hard to tell from the pictures how mixed up the air is coming off of the back of the 73. I would like to see a video of both to see if there is a difference between the rubber bumpers and the chrome bumpered cars. (It would be interesting to see Pacer style C3's compared also.(78-82))
I'll see what I can do Saturday...
06-23-2006, 12:23 AM
#100
Originally Posted by JPhil
"Stringray"!
I love it, I'll wear that moniker with pride! To be honest, I haven't really had time to study these closely yet myself. I wanted to do some open headlights & windows shots, but I figured we were pushing our luck with what we got, plus I plain forgot.
Thanks Rich for your help.
John
Hey..related topic..I took my 78 Sa out today to test A/C,coolant temps as it was 90's+ F today....running 75-80 A/c on,coolant temps were 205...and stable...comimg back,I reduced speed to 65...and temps dropped to 199 F....I think the over radiator air ducts are robbing air from the radiator at higher speeds...my next experiment is to dis-connect those ducts/tape inlet,and see what happens to coolant temps with A/c on in that mode...if they are lower...?????Then I have to figure out a mod..
Rich