Aerodynamics

[rqb4000]

I would like to begin a dicussion of aerodynamics. How does the Avanti rank with modern cars ? How about cars of the '80s ? I am sure I've read in either Studebaker or Avanti publications what exactly the rating of the avanti's wind resistance. But I'm sure I wouldn't know where to find such info. now.

Apparentl when Andy Granetelli was testing an Avanti, the rear window popped out. What caused this to happen.

When I see articles about the Bonneville Salt Flats, I see plenty of '53 Stud. coupes.

Does a website exist that gives aerodynamic ratings.

I look forward to others thoughts and sugestions.

[Gunslinger]

The rear window would pull out for a couple of reasons. The shape of the Avanti creates a vacuum behind it...it gets worse as the speed increases. Combine that with what was determined to be insufficently secure rear window attachment points and the vacuum sucked the glass right out. Supposedly having the side windows open made the problem worse allowing blowing air inside the car pushing even more on the glass from the interior. Studebaker made at least two modifications toward improving the rear glass brackets to eliminate the problem. I may be wrong on some of these specifics, but I think it's basically what happened.

As far as aerodynamics go, I'm not aware of any testing, either back then or now, done on the Avanti design, though the Avanti design seems based on practical aerodynamics. There was little known of items taken as normal now, such as spoilers and air dams to push the air around the car rather then allow it underneath creating turbulence. I read that the Due Cento, when raced at Bonneville, had complete belly panning installed to alleviate the underbody turbulence. I feel sure a good spoiler mounted under the front end would go far in getting more cooling air to the radiator rather than create under chassis turbulence. I believe someone in the club has posted a thread in the past doing just that.

In one article I've read on the Avanti, the author said Porsche engineers said the Avanti has long been their favorite American design due to its aerodynamic design. I have that article somewhere...it was written some years ago.

'53 Studes have always been popular at the Salt Flats due to their shape. A beautiful design that didn't sell well way back when. Sometimes it's true when people say that Stude designs were often ahead of their time.

[SBCA96]

The rear window popping out was an early production problem, and it was

supposedly ONLY when the windows were down at speeds over 100 mph.

An easy solution is to leave the windows up when going over 100 mph.

http://www.theavanti.com/AmazingFacts.html

It's a fact: The Avanti drag coefficient was estimated in the high 0.30's when most stock American cars were in the 0.50's

http://www.theavanti.com/Racing.html

Tom

[rqb4000]

I did some sufing on the net. Found some drag-coefficient #'s for some cars that can be compared to the Avanti: 2004 Toyota Prius ( 0.26 )

2007 GMC yukon Denali ( 0.36 )

current design Honda Accord ( 0.30 )

It's predessor ( 0.33 )

VW Beetle ( 0.38 ) I don't know if original design or current design

Hummer H2 ( 0.57 )

'48 Tucker .... mathematically computed ( 0.27 ) 'Rounded Up' publicly to ( 0.30 )

2002 Acura NSX .... " weight and aero. improvements take drag from ( 0.32 ) to ( 0.30 )

Gentlemen, these are few examples. At the website 'wikapedia' I found a whole definition of drag. Components like weight, frontal area, high pressure, low pressure,... it's more complicated than the female reproductive system. And almost as exciting!

Other views are welcome

John

[DEEPNHOCK]

I know of several Avanti's that had the rear window come out at speed, and they all had the windows up.

The additional two window clips solved that.

Jeff

The rear window popping out was an early production problem, and it was

supposedly ONLY when the windows were down at speeds over 100 mph.

An easy solution is to leave the windows up when going over 100 mph.

Tom

[Avanti kid]

Very interesting question on the Avanti aerodynamics and it's rear window. I have some experience on both, first the Avanti is very good in aerodynamics except for the front window that is horrible, as I lower the front of the car to put it on a California Dago rake the window gets steeper making its aerodynamics worse. I need the front low and rear higher for better control above 150 mph. Even at 201 mph the cars is stable with this rake and the 650 lbs of balast I added to the car for better traction. So, as result the car is very good except for the front windshied. However I believe the 53/54 Studebaker coupes are far better in aerodynamics than the Avanti. As far as the rear windshield coming out at speed, we have experience of that when Jim Lange drove my Avanti at Bonneville and was doing about 175 mph when the rear window was sucked up into the air about 50 ft and broke into little pieces. We had to shut down racing on the salt for one hour while everyone was picking up glass! I had to buy a lot of beer for the racing officals that day, ha-ha. This window came out even with small tabs added to help support the window. Now afte that experience we made our own window out of Lexan and bolted it in place, no more problems. The main reason for the window blowing out with windows up and rear vents open, is the air on top of the window at high speed causes a huge suction. Now with the Lexan bolted in the car roof is even stronger.

Take care, Dave Bloomberg "Avanti kid Racing"

[tsheard]

The rear window would pull out for a couple of reasons. The shape of the Avanti creates a vacuum behind it...it gets worse as the speed increases. Combine that with what was determined to be insufficently secure rear window attachment points and the vacuum sucked the glass right out. Supposedly having the side windows open made the problem worse allowing blowing air inside the car pushing even more on the glass from the interior. Studebaker made at least two modifications toward improving the rear glass brackets to eliminate the problem. I may be wrong on some of these specifics, but I think it's basically what happened.

As far as aerodynamics go, I'm not aware of any testing, either back then or now, done on the Avanti design, though the Avanti design seems based on practical aerodynamics. There was little known of items taken as normal now, such as spoilers and air dams to push the air around the car rather then allow it underneath creating turbulence. I read that the Due Cento, when raced at Bonneville, had complete belly panning installed to alleviate the underbody turbulence. I feel sure a good spoiler mounted under the front end would go far in getting more cooling air to the radiator rather than create under chassis turbulence. I believe someone in the club has posted a thread in the past doing just that.

In one article I've read on the Avanti, the author said Porsche engineers said the Avanti has long been their favorite American design due to its aerodynamic design. I have that article somewhere...it was written some years ago.

'53 Studes have always been popular at the Salt Flats due to their shape. A beautiful design that didn't sell well way back when. Sometimes it's true when people say that Stude designs were often ahead of their time.

Volvo engineers found that the shoulders running along the sides of their cars mitigated much of the lift caused by the wing effect of air rushing over and under the car. They were able to offer cars with no rear spoiler that did not have a signifcent lift on the rear of the car at speeds. I suspect that the Avanti's long shoulders have a similar effect and prevent the rear from lifting at speed.

Tim Sheard, Brooklyn

[Geoff]

Air can be considered our frienemy. It’s an enemy when we desire to punch through it to travel faster though it’s extremely necessary to have. Luckily for us we can manipulate it; we can coerce it to go places and do the things we want it to do while it puts up a fight. I am curious about some aspects of Avanti’s aerodynamics.

First, pertaining to the rear window being sucked out. What about vortex generators as seen along the rear roofline of some Mitsubishi Lancer Evolution models? They’re not specific to the Lancer and are more often found on aircraft.

Vortex generators redirect the boundary air layer so as to keep it from abruptly separating and causing a turbulent region. In the Lancer’s case they redirect the airflow downward along the rear window. Without them, the air detaches from the roof and tumbles over the car’s rear. They also happen to increase the air velocity over the Lancer’s rear wing, an item Avanti doesn’t have. As a side, the TVR Sagaris has a clear spoiler affixed to its very curvaceous rear. I wonder if Avanti would benefit from a similar design?

Some research and development would need to be undertaken to design and install vortex generators on an Avanti. I have heard their design and how they are mounted angles the air various degrees. In short, the ones designed for Lancer wouldn’t be as effective as on other cars. If an Avanti were to have vortex generators, would the redirected air flowing closer to the rear window help keep a turbulent low pressure zone from sucking it out?

Next, air flow management under the car. Sporty cars rake the radiator, some push the top forward others recline the top. I understand this is primarily to increase the radiator’s surface area relative to air flow, though a side benefit is a lower hood line. Some cars like the Cobra Daytona [coupe] utilize an isolation box and hood design to suck air through the radiator. Then the airflow is directed over the car rather than allowing the air to remain under the hood and causing an eddy at the firewall or continuing to travel beneath the body.

Avanti slopes its radiator forward, I would use that and borrow a page from Cobra Daytona. On an Avanti being prepared for sustained speed, I would: remove the engine driven fan and stock fan shroud, install an electric fan in front of the radiator, redesign a hood that starts to "waterfall" as soon as it clears the front of the engine and accessories, create an isolation box in place of the stock fan shroud and be sure it contacts the hood. The idea is to not let air remain under the car, to force air through the radiator and out over the top of the car.

The new Z/28 and other cars use a rectangular opening with louvers in place whereas some, like ALMS race cars, the new Viper, and the Shelby Series 1 have design elements built into the hood for the same purpose.

Cars built on Studebaker frames have an integrated x-brace and the exhaust pipes route through the cross. This means the exhaust piping does not hang lower than the frame and a belly pan could be fitted, at least from the firewall, back. Ceramic coating and/or insulation wrapping of the exhaust pipes would be recommended to prevent exhaust heat from becoming trapped between the cabin floor and the belly pan. Once a belly pan is fitted another idea would be to add a rear diffuser.

Lastly, air trapped in the engine bay. Some cars use air extractors placed along the front fender. Many examples I’ve seen are low and behind the front wheel well, exemplified on Corvette and front engine Ferraris, while others are up high on the fender such as on Plymouth ‘Cuda and 1970s Firebird. I don’t know exactly where it would make sense to alleviate any trapped air under an Avanti hood, though once some research was done (GoPro camera and yarn affixed under hood), it could be found out.

Most of what I discussed makes sense for a racing Avanti, whether it is one set up for Bonneville top speed or one suited to road course racing like the Mid-Ohio car, and some of the ideas could be implemented on a daily driven Avanti. I would apply these to a blended bumper Blake car, as he was pretty focused on putting Avanti back in racing. Now I just need some money bundled with space and time to make it all happen.

In the below game graphics, generally speaking red lines represent air surrounding the car while blue and green lines represent air passing through various car orifices. Dashed lines represent air that has come through an orifice. In the case of the Mitsubishi pictures, red line / blue line rules don't apply. The red line more accurately portrays how the air would flow without vortex generators.
Mitsubishi related material:
PDF written about Lancer's vortex generators [top of fifth page has good comparison graphics]
Motor Trend vortex generators picture
Mitsubishi Lancer Evolution vortex generators, elevated rear side view
Mitsubishi Lancer Evolution vortex generators side rear view
Air Tab [different than vortex generators though they also manipulate air flow]
TVR Sagaris picture:
Sagaris' rear view
Cobra Daytona coupe pictures:
Front 3/4 view, hood up
Shelby Cobra Daytona Coupe front aerodynamics, forward roof view
Shelby Cobra Daytona Coupe aerodynamics, elevated forward 4/5 view
Examples of hood air extractors:
2014 Z/28 hood extractor shown in action
SRT Viper forward roof view, bonnet/hood closed
SRT Viper forward roof view, bonnet/hood erased [to display where air extractors are "vacuuming" air]
Corvette C5R front aerodynamics, forward roof view
Corvette C5R front aerodynamics, front view
Corvette C6R front aerodynamics, front view
Shelby Series 1 front aerodynamics, front view
Examples of fender air extractors:
Firebird Trans Am side aerodynamics, rearward front side view
Firebird Trans Am side aerodynamics, forward rear side view
Plymouth 'Cuda side aerodynamics, forward rear side view
Plymouth 'Cuda side aerodynamics, rearward front side view
Examples showing both extractors:
Corvette C5R aerodynamics, side 4/5 view
Corvette C6R aerodynamics, elevated side view
Shelby Series 1 aerodynamics, front side view

Edited September 20, 2014 by GeoffC312

[PackardV8]

Aero then is what it is and aero now is a continuously evolving science.

Look at some of the high performance cars contemporary to the '60s Avanti. All of them, Jaguar XKE, Sunbeam Tiger, Shelby Cobra, have near vertical windshields.

Then look at the most aero performance cars of the past ten years. The Gen III/IV Camaro/Firebird come to mind. The windshield lays much more toward horizontal and the front comes to a large radius elipse. There's a belly pan which extends behind the front bumper and they sit six inches lower than the Avanti.

Bottom line, only by the standards of the '63 Ford Galaxy could the Avanti be considered aerodynamic. It's just less bad than most early '60s cars. A Camaro/Firebird/Monza with the same horsepower would probably be 20-40 MPH faster.

jack vines

[Guest dapy]

While unscientific at best...think of a car as an airplane wing. Trouble with the wing analogy is the uninterupted top and bottom airflow creates the pressure difference that provides lift. Cars need to stay on the ground. So streamlining a car may require bottom and top wind deflection that modifies the "streamlining'. Design science has come a long way. However safety and convenience override speed. Race cars don't care.

The Avanti was said to have no straight lines, or sharp edges (a complement to Mr. Loewy). That design might reduce the wind stream vortexes that slow the car. However fast or slow...an Avanti 'looks' fast at rest.

Edited November 8, 2013 by dapy

[Geoff]

Aero then is what it is and aero now is a continuously evolving science.

That ties in to my thinking. Apply what has been learned to a car that could benefit from time's lessons. The Avanti has a problem with the rear window getting vacuumed out, and air under any car is bad. These can be rectified using knowledge gained between when the car was first drawn on paper and today.

Avanti, even with its near vertical windshield, is estimated to have a Cd in the high 0.3 range. A number respectable even today. New pony cars like 1999 Mustang (0.36) and 1995 Camaro (0.338) are better though not by as wide a margin as one might expect. That tells me the Avanti's body does a very good job of displacing air since we know the windshield isn't helping matters. Under that closed hood I bet there are turbulent regions at the firewall and under the passenger compartment.

Lowering an Avanti isn't difficult. I would fit an '84 or '85 with 275/40-17 wheels & tires and would lower it on stiffer springs in a coilover setup. I couldn't get it 4th gen. F-body low though it would be lower than stock and that would be an improvement. I would also custom design a hood to reduce the quantity of air in the engine bay, and would glass-in some fender extractors to keep the air that does get in from going under the car.

As with many things, research and development would have to be undertaken to maximize the effectiveness of any change made to a car's body but it's not impossible. What if the culmination of aerodynamic tweaks: lowering the car, an air dam feeding an air extracting hood, fender air extractors, a belly pan, vortex generators, and a rear diffuser, could take Avanti's Cd from [let's use 0.38 for simplicity's sake] to 0.35 Cd or less? That takes the car to first gen. Viper GTS (0.35) and C6 ZO6 (0.34) levels. It would be interesting to see further research into this, even if it is in a CAD program and computer aerodynamic simulations to start.

[PackardV8]

Avanti, even with its near vertical windshield, is estimated to have a Cd in the high 0.3 range.

If we're going to have a serious discussion of aerodynamics, we can't begin with garbage-in-garbage-out, so that "estimate" has to be substantiated. Where and by whom is the source of this estimate? What are his credentials and by what method was the estimate derived? Do we have a published frontal area? For example, Road&Track 1963 Road Test published a figure for the Avanti of 160 pounds of drag @ 60 MPH. This isn't exactly aero, as it is the highest for any 1963-64 car they tested - actually higher than the full-sized Mercedes and Jaguar sedans. For comparison, with say the '63 Corvette at 120# and the Sunbeam Tiger at 105#. The small frontal area cars were under 100# total drag @ 60 MPH.

I would fit an '84 or 85 with 275/40-17 wheels & tires

Wider tires substantially increase the frontal area as well as rolling drag. While the 40-aspect-ratio is lower than the OEM 80-aspect, The 275/40-17 is actually about the same height as the original Avanti 6.70x15" , but is 45% wider, thus more drag. jack vines

[Geoff]

… Andy Granatelli, President of Studebaker's Paxton Division, prepared several cars to make USAC-sanctioned record attempts at Bonneville late last winter and although most of the trials were frozen out by bad weather, he did manage to make some official two-way averages with a Lark, a Hawk and an Avanti, all equipped with R2 engines and four-speed transmissions. The cars were completely stock including exhausts. Naturally, they were tuned to the highest degree. The Lark averaged 132.04 mph. The Hawk, with its sleeker body lines, averaged 140.24 mph. The Avanti, a real slippery customer in the aerodynamics department, averaged 158.14 mph through the flying mile. With everything else equal, it proves how important body shape can be …

I thought it was more widely known Raymond Loewy had a good handle on aerodynamic design.

It's a fact: The Avanti drag coefficient was estimated in the high 0.30's when most stock American cars were in the 0.50's.

I used this quote as my basis though I don't know who arrived at that estimate or by which method. I am curious and would like to know a solid answer, primarily for the Studebaker but then also for the Newman/Altman, Blake, and Kelly/Cafaro generations.

Let's compare three vehicles: 1969 Opel GT, 2010 Subaru Impreza WRX, and 1999 Mustang. All achieve a Cd of 0.36 via different sizes, shapes, profiles, and stature.

Regarding my tire choice: I'll accept the drag and rolling resistance hits because I'm in the American minority; I prefer road course racing where higher lateral grip is desired. If I were to build the car for a sustained top speed run I would select narrow tires and cover the exterior of the wheel wells as much as reasonable. In both cases I would fit an air dam spanning the whole front width, tires included. True, an air dam increases frontal area which increases drag. Also true, an air dam reduces air traveling under the car which decreases drag. I had a conversation with a friend who took fluid dynamics courses and he told me air is easier to displace horizontally than it is to displace vertically; the part of the air dam in front of the tires works to displace air horizontally.

[PackardV8]

Until we have a frontal area data point, we're just bench racing.

As for Lowey's "handle on aerodynamics", he was a stylist with a good eye and a successful self-promoter. (Way OT, but when I watch Mad Men, I keep looking for the RL episode. He was a uber-Mad-man.) Under his watch my all-time favorite cars and trucks came out of Studebaker, but he had zip training in aerodynamics. He knew what looked fast, as opposed to what is fast.

What looks slick may or may not be slick. For example, the 1975-80 Chevy/Olds/Pontiac/Opel Monza, an ugly little pumpkinseed of a car, is much more aerodynamic than the '53 Studebaker or '63 Avanti. Who'd look at a Subaru Impreza and think aero? However, it has the same coefficient of drag as the much slicker-looking classics such as the Citroen DS21, NSU Ro80, Viper and Jaguar XKR.

I'm still looking through the old literature for a frontal area figure for the Avanti. When we know that, we can calculate the actual coefficient of drag and the horsepower required for 60, 120 and 220 MPH. It won't be pretty.

jack vines

[Geoff]

Andy Granatelli took the Avanti to Bonneville and easily set a slew of international speed records. Mickey Thompson was after the same ones with a hot 421 tri-power Pontiac that probably had some 100 hp on the Avanti. But what gave the Avanti the advantage was its drastically more aerodynamic body, estimated to have a Cd of “in the high 0.30s”, as well as a much smaller frontal area.

-http://www.curbsideclassic.com/curbside-classics-american/curbside-classic-1963-studebaker-avanti-flawed-brilliance/

It's 21.1 square feet according to http://www.theavanti...dimensions.html. I am finding that frontal area is not the whole picture when it comes to drag, it plays a role though using it alone is a rudimentary way of discussing drag. There's more to the equation. We really need an Avanti in a wind tunnel for a solid answer.

"There is a lot to drag than meets the eye. What happens underneath, how the radiator air is let in and out. How the rear of the car is shaped all have a big input on the drag."

above quote from busman, here: http://www.planet-9.com/987-cayman-boxster-service-tech/8956-drag-coefficient-cd.html. They're discussing select Porsche models though their conversation gets into Cd. One of the members even has a '63 R2 Avanti.

Who would look at an Impreza and think aero? Bingo! It attains 0.36 Cd and yet to some people it wouldn't appear so. Could Avanti be 0.38 and yet to some people not appear so?

Here's a comparison to think about:

The C6 Corvette ZR1 can reach a speed of 205 MPH. It does so with 638 peak horsepower and a Cd of 0.36 [which is higher than other C6 packages because ZR1 adds ground effects].

How much power did the R5 produce … circa 575? An Avanti with R5 could peak at 196 MPH.

Edited November 11, 2013 by GeoffC312

[Gunslinger]

You're not quite comparing apples to apples. I've seen figures of 575 hp and 638 hp quoted for the engine in the Due Cento. Whatever the actual measured horsepower was, it was measured in gross horsepower...the ZR1 Corvette is rated at 638 net horsepower...two different animals.

The ZR1 has the benefit of computer designed everything, plus computer controlled engine management. The Vette also didn't race on salt and the Due Cento didn't race on a track. The Avanti had full a belly pan to reduce turbulence and the ZR1 has advanced air dams, etc., to move air around the car rather than under it. The difference in tire technology, engine management, chassis design, etc., are also worlds apart. The Vette also has air conditioning, power windows and a slew of other power accessories the Due Cento did not.

Modern technology has allowed Avantis to break the 200 mph mark...but are they streetable cars? They're highly developed and specialized cars designed to do one thing and one thing only...go fast in a straight line. The ZR1, with the advantages of modern technology...and no small amount of GM engineering money, can go fast in a straight line, handle a road course and brake as effectively as it accelerates. It can also be docile on the street.

I'm not knocking the Avanti design, its designers and those who still take them to the salt, but it's simply not a fair comparison. Two different cars from two different generations of design and engineering and two different styles of racing don't make for equal comparisons.

Edited November 11, 2013 by Gunslinger

[Geoff]

Gross horsepower and net horsepower are both flywheel rated. Net takes into account the engine driven accessories with an "as-shipped" exhaust system attached. Gross is an engine without accessories and an open exhaust system. Neither rating takes drive train losses into account. On a dynojet, a stock ZR1 shows 535 horsepower to the road. 638 to 535 is ≈16% loss of power, in the range I've heard to account for drive train losses.

I completely agree about the ZR1, it's an amazing creation. Isn't technology wonderful? These are the only aspects I was comparing: 0.36 Cd for the ZR1, 638 horsepower, and a 205 mile per hour top speed. As in, the Corvette ZR1's design took 638 net horsepower (along with its 6 speed gear box, lightweight driveshaft, air conditioning, 1.10 lateral-G rating, etc.) to attain 205 miles per hour.

I also have read the Due Cento engine made 638 horsepower. Since this is grossly rated then it is not equal to the ZR1's 638 horsepower and would be less power in reality. Maybe that's where the 575 figure originates, as somebody's guess converting to net? Even that would be high compared to what the tires put to the ground, so now R5 is down to the 490 horsepower range.

…Driven by Joe and Andy Granatelli, the Due Cento reached speeds well over 200 mph according to the tach, but was not getting traction due to the wet salt and the best official run was 196.58 mph …

If the Avanti is not even in the same aerodynamic ballpark as the C6 ZR1 (which is 0.36), how could an Avanti body be approaching 200 miles per hour? Especially with only 638 gross horsepower, which we agree is less than the C6 ZR1's 638? Keeping in mind a Bonneville rating is a two-way average, so a 196 average means equal time spent at 192 as 200 or 190 as 202.

http://www.studebake.../duecento2.html

http://www.studebake...to/dcind2d.html

[Guest dapy]

I grew up in South Bend and my best friend's father was #2 at Studebaker. Met RL there in 1948-49. Dapper. Looked a little like Salvador Dali.

My early career was on Madison Ave. (That's where the name MAD MEN came from.) I happened to work at the ad agency that had the Studebaker account. (No it wasn't nepotism.) I was there when Studebaker was searching for a name for a new model. That was the first HAWK. Yes, I know this dates me and is not aerodynamic. The end of this story is I bought a 1962 GT Hawk. You can see it now at ebay.

[Geoff]

As I was perusing through some files I stumbled across a .pdf of the owners manual for the Escort GT2, a personal accelerometer device. I never had Escort's device though I did have one from a competing company. I don't believe the GT2 is made any longer but the Escort website still hosts the literature and may be found here under Vehicle Performance Meter Owner's Manuals.

Pages 21 - 23 of the owner's manual discuss C_DA. The owner's manual also gives a method for finding your car's C_DA, posted in screen captures below:

If you know or can find your car's weight, and if you have access to a straight, flat road where "slightly above 60 MPH" is not dangerous and/or illegal, it is possible to find C_DA following the directions written above.

[boogieman]

Very interesting.

Boogieman

[Geoff]

If we're going to have a serious discussion of aerodynamics, we can't begin with garbage-in-garbage-out, so that "estimate" has to be substantiated. Where and by whom is the source of this estimate? What are his credentials and by what method was the estimate derived? Do we have a published frontal area? …

I found something! "… with a smaller frontal area of only 21.1 sq. ft." (which jives with the dimensions found on theavanti.net) and "… so far as I know, the drag coefficient must be in the high 0.30s in comparison to the Pontiac's 0.53 or the Corvair's 0.43." Article authored by J.T. Crow of Car Life magazine http://www.studebaker-info.org/AVDB3/duecento/cl64granatelli.jpg

Edited February 24, 2015 by GeoffC312

[Geoff]

Last hurrah-

Raymond Loewy had more than just fleeting knowledge of aerodynamic design:
"Loewy emphasized … accent wedge-shape … pinch waistline, as le Mans-type racing cars … above all, think aerodynamics."
Also, we may "thank" Egbert for changing the windshield rake; the car was designed to have more slope. Even so, apply some Cobra Daytona Coupe A-pillar air deflectors to prevent the windshield from throwing off a large wake; big problem becomes little problem.
From http://www.theavanti.net/design.html and http://www.theavanti.net/birth_window.html

I concede that applying what had been learned aerodynamically to cars was still in its toddler years, though some knowledge had been gained. German aerodynamicist Wunibald Kamm discovered how to reduce automotive drag in the 1930s and due to his research we have the Kammback / Kamm tail / K-tail. So while it's possible Loewy had zip training in aerodynamics, it's likely he was astute, paid attention to the world around him, and learned without being in a classroom.

Pertaining to the notion of adding aerodynamic enhancements to a car after the fact:

1969 Dodge Charger R/T vs. 1969 Dodge Charger Daytona. The R/T has a drag coefficient of 0.51*. After body modifications, the Daytona model achieves 0.33* (this allpar.com story lists 0.28). By adding a nose cone, placing air extractors above the wheel wells, and flush mounting the back light, Charger's Cd drops 0.18 points. If not for the addition of its wing the figure would be better. There's also an intermediary Charger to these two, the Charger 500. That car pushed the R/T's grille forward and flush mounted its back light. I don't have an official number here, I guesstimate it to be between 0.47 and 0.43. By manipulating air where we want it to go and (even more important) preventing air from bunching up and swirling, improves cars without these design elements.

(* numbers pulled from a racing simulator's game disc information, Forza Motorsport 4.)

[Geoff]

Ron Rifkin posted to the Avanti Owners Association Facebook page, with an attached image of the book Industrial Design Raymond Loewy.

"I remember when the chief engineer of Porsche in Stuttgart asked me, 'Loewy, how did you wind-test the Avanti?' I said 'Why do you ask?' 'Well, we know a little here about streamlining and your Avanti is almost perfect, no parasitic noise at high speed, skin friction reduced to practically nothing.' I said, 'I didn't test it at all.' He couldn't believe it. 'No', I said, 'I did it by feel and design intuition.'"

-- R.L. in a 1978 interview, in this excellent book.

 

So there's a solid answer about Loewy. By his own admission he went by feel and design intuition. I would argue a little though that he was aware of tried and true aerodynamic cues, which had been implemented on cars meant for speed.

[Footer]

Very interesting thread even though I don’t drive my car over 100 mph.  I am, however, amazed that I can drive the Avanti down the road at 45 mph  with the windows down without my wife complaining about her hair getting mussed.  The buffeting in our Grand Cherokee at the speed will about rupture an eardrum!  Mike

[Nelson]

On 11/10/2013 at 12:34 PM, PackardV8 said:

What looks slick may or may not be slick. For example, the 1975-80 Chevy/Olds/Pontiac/Opel Monza, an ugly little pumpkinseed of a car, is much more aerodynamic than the '53 Studebaker or '63 Avanti. 

Don’t know how you can make this judgement call when we don’t have the drag coefficient numbers for the 53 Studebaker or the Avanti? No offense and you maybe correct but this statement is your assumption not based on comparing facts.😊