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Old 05-08-2017, 10:27 AM   #1 (permalink)
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Corvette c3 cd of 0.55 to improve

I have been hovering around this site for a while and finally at the stage where I need to get specific with my needs on aero as it is my daily too.

Have a corvette c3 1982 (actually most aerodynamic c3 made, think it is about 0.45cd) and lightest, I have done a lot of custom stuff to it, ls1, 4l60e, 2.73 diff gear, massive tyres (about 10% larger diameter) and then a lot of other stuff like adjustable coil overs, hydroboost, steering system, aircon delete etc)

Now with a cammed ls1 I go 0-60 3.8secs so I hit 100mph in 9seconds, so I would like some stability and downforce to make the aerodynamically unstable CD of 0.45 hit terminal speed faster and better, with the added benefit of being fuel efficient

Needless to say I don't want to modify the body too much. I have a lowered front lip, and thinking about a belly pan (worth it with the lowered front and lip?)
Thinking about adding an actuator to lower the lip at 30mph and higher.

It is a car that did not harness aero, so anything even basic should be an improvement. And I know it is very capable, as on long trips at 60mph I get 48mpg, engine barely goes over 1300rpm cruising at those speeds and weighs 2700lbs, fuel efficiency is obviously a different story when I want to have fun, but makes me think if I get pretty decent efficiency cruising now imagine if I got the .45 cd down to .3.

Perhaps someone can upload some pics of the 80-82 to show the flaws like the parachute bumper, front lip, side vents, etc

Like to hear what you guys think would be beneficial without ruining looks and while creating downforce and not disrupting airflow to cool the radiator.

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Old 05-08-2017, 06:43 PM   #2 (permalink)
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The corvette isn't an aerodynamically slick car, never has been, and if it is now, it hasn't been until recently. The main focus is on downforce and cooling.



this is supposedly the underside of your car. This is likely going to be the focus of your efforts, as the top is pretty well smoothed.

you want this as smooth as possible, ideally a solid sheet of aluminum or coroplast supported by standoffs. if a solid sheet isn't practical, getting as close as possible to the lowest hanging objects (exhaust, cross members, ect...) supported by standoffs.
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Old 05-08-2017, 08:14 PM   #3 (permalink)
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under belly pan for 02 Q45
go here and look at the pics.
Pretty detailed in how to install a belly pan to smooth the bottom
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Old 05-08-2017, 08:28 PM   #4 (permalink)
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I would do full belly pan and maybe some spats for the front and rear wheels. Get some Carbon Creations GT-C mirrors if you can find them and tolerate them (maybe delete the passenger side one if you can). I would say aero on the top of the car would be decent. If you have louvers, remove them as it may affect the ability of air to stay attached as long as possible. The sides where the air separates at the back I'd put one air tab on each side half way up to the top of the trunk. Maybe an underbody diffuser at the back after that and I see someone's done it.

For other ideas on efficiency, get some lightweight flow formed/rotary forged wheels and low rolling resistance rubber - I love Nokians. Do the electric fan mod (volvo 2 speed controller, bmw 2 speed sensor, a relay, some wiring and a 2 speed Taurus/TBird fan). Find aluminum drive shafts if you can. Again for lower rotational mass. Run low viscosity synthetics and use ws2 and nmf wherever you can.

Always have fun!
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Old 05-08-2017, 09:20 PM   #5 (permalink)
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Old 05-09-2017, 09:03 AM   #6 (permalink)
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I was a little stumped when I saw this thread yesterday morning. All I could think of was a belly pan under the restrictions but felt it may not be enough. I've changed my mind about that based on the Audi claims below.

I'm really impressed with the responses covering the wheels and pans.

https://www.audi-technology-portal.d...tics/underbody

Quote:
A car produces 40 to 50 percent of its total aerodynamic drag in and around the underbody, the wheels and the wheel arches..........
There was a thread recently which explored the leading edge of the wheel wells as a drag reduction area. I'm wondering if this project is a candidate in that the modification could be made rather subtle.

What I have in mind would be a flat piece of rubber in an arc shape which closes up the wheel gap and forms a clean release edge for the air. Being black in color it may not be all that noticeable.

To understand the desire for such an apparatus (flare/molding) look at CFD images which include wheel wells.

Maybe there is something in the JC Whitney catalog which can be chopped up?
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Old 05-09-2017, 09:52 AM   #7 (permalink)
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the rear wheel arches could easily be sealed with stiff rubber or plastic cut to shape with tabs to secure it to the arch. in front of the wheels should be a straight or slightly curved (straight is fine, easier to make, and used by auto makers), but the distance in front of the wheel is the trick, and I'm not sure if anyone here has figured that out.
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Old 05-09-2017, 10:18 AM   #8 (permalink)
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The JC Whitney rubber flares are pretty flexible, the flat one even more so than the arched ones. Therefore I'm guessing that even if one is off a little it would just flex out of the way.

A picture is worth a thousand words, keep in mind the rubber would be black and be nearly invisible from a distance.

http://s184.photobucket.com/user/kac...?sort=3&page=1






The reason I did not show this thing going all the way around equal distance, and equal parts exposed is that the air needs to get out of the wheel well. I'm just proposing that the leading edge gets treated. Again, research some of the other forum topics similar to this.

This is the image I was looking at when I did the sketch.

http://www.buyavette.net/1882C%201982%20Corvette.php


These are large air gaps by today's standards, unless we are talking trucks - those have gotten many times larger. I'm thinking current sports cars, but of course they have different suspension systems than the 1980's.
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Last edited by kach22i; 05-09-2017 at 10:24 AM..
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Old 05-09-2017, 04:24 PM   #9 (permalink)
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Welcome to Ecomodder.

Quote:
Needless to say I don't want to modify the body too much.
...
I want to have fun, but makes me think if I get pretty decent efficiency cruising now imagine if I got the .45 cd down to .3.
...
Like to hear what you guys think would be beneficial without ruining looks and while creating downforce and not disrupting airflow to cool the radiator.
Needless to say ... you don't want to hear what I have to say.

Which is your goals are at cross-purposes. To get to 0.30 Cd, you will need to improve the looks. Sorry, that's just the way it is.

Long story short: Stanced with a shooting brake/boat-tail.

https://www.google.com/search?q=stanced+C3+Corvette




Edit: Almost forgot, if you are looking for downforce without adding drag, look to the VW GTI W12-650:



You can keep the stock top and add sail panels and a wing without adding frontal area. Similar to the new Ford GT40.

Thanks kach22i, although I prefer the red Audi floorpan pic:



Could you sketch up a 'Vette with a Charger-style wing that fits within The Template? It would be narrower than the taillights and a little taller than the stock spoiler. Pleeez?

Last edited by freebeard; 05-09-2017 at 04:48 PM..
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Old 05-09-2017, 06:36 PM   #10 (permalink)
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Would a larger (15% taller) tire close the gap as effectively as that too? I do have large tyres and a lowered Vette, to the point where the back tyres sit an inch in the wheel well and fronts have virtually no gap.
And my front stock air dam does come infront of the front tyres all the way down to 4 inch from the road, so I think that would do an effective job as a spat.

One area that may be a big one for aero is the rear bumper, I removed the spare tire carrier so the bumper is now a big plastic parachute, I was thinking of cutting out the area of where my licence plate sits, hinge the bottom of the licence plate, and install an actuator pushing the top of my licence plate to a 45deg angle when I am above 50mph to vent the buildup into the wake of the bumper. Would that work? Anyone done anti parachuting without hacking up the bumper?

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