Fuel Economy And Aerodynamics: The Yin And Yang Of Car Design

From the classic Model T to the iconic American muscle cars, the design of cars has been shaped by many factors over the years. Technological advancements, consumer preferences, and government regulations have all played their part. But one factor that has been a game changer is fuel efficiency. The Corporate Average Fuel Economy (CAFE) standards, introduced in the aftermath of the 1973 oil embargo, have pushed car manufacturers to focus on fuel efficiency. Initially mandating a modest 14.2 mpg average, the CAFE standards have since been updated, with the current goal being a fleet-wide average of 58 mpg by 2032. As car manufacturers strive to meet these ambitious targets, the role of aerodynamics has become increasingly important. In the past, scaled-modeling techniques were used to test and refine car designs. Today, sophisticated computer simulations, such as computational fluid dynamics (CFD), are used to optimize cars’ aerodynamics. So next time you admire the sleek lines of a modern car, remember that it’s not just about looks – every curve and contour has been carefully designed to maximize fuel efficiency and minimize air resistance.

Delving into 100 years of car design

1900 – 1930

In the early 1900s, cars were not designed with particular aesthetics in mind. They were primarily built to be practical and utilitarian. The introduction of the Ford Model T in 1908, the first mass-produced car, changed the face of the automobile industry forever. The Model T had a four-cylinder engine and a fuel economy of around 13 to 21 mpg, slightly lower than today’s average car. But what set it apart was its affordability. In just a few short years, the price of the Model T dropped from $780 in 1910 to a mere $290 in 1924. This was made possible by the savings that were achieved through mass production.

Ford Model T

1930 – 1940

The world entered the 1930s amid the Great Depression. The stock markets had crashed, and the American automobile industry was hit particularly hard, where new car sales plummeted by 75%. To make matters worse, the price of fuel had fallen drastically, from 30 cents per gallon in 1920 to just 21 cents in 1929. The production of cars also took a hit, dropping from 5.4 million in 1929 to 3.4 million in 1932.

Clearly, something needed to be done to make cars more cost-effective. That’s when the automakers started thinking about aerodynamics. Instead of changing the engine, they streamlined the cars’ designs to make them more efficient. Inspired by aviation and Art Deco, the new car designs favored a clean and simple look. The mid-30s saw the birth of some of the most iconic aerodynamic vehicles, including the Volkswagen Beetle, the American Chrysler Airflow, and the Phantom Corsair of 1938.

1935 Bugatti Type 57 Grand Raid

1940 – 1950

During the early 1940s, the outbreak of war forced automobile manufacturers to shift their focus to producing parts for military vehicles. As a result, the production of household cars came to a halt, and car ownership plummeted by 73%. However, World War II veterans began engaging in drag racing during this challenging period. It wasn’t until the 1950s that the first official drag race was held at a Santa Ana airstrip. The competition quickly gained popularity, and in 1951, the National Hot Rod Association (NHRA) was established to oversee numerous racing clubs across the country.

With the war’s end, the automobile industry underwent a small revolution by introducing pontoon styling. This new style served as the basis for contemporary car designs. However, these pontoons added considerable resistance, resulting in a lower average mileage of 15 to 20 mpg.

1950 – 1960

In the 1950s, the world of automotive design was divided. American car designers were all about the future, taking inspiration from aviation and spacecraft to create angular and boxy designs. Meanwhile, their European counterparts were obsessed with the science of aerodynamic drag, trying to make their vehicles as streamlined as possible.

Jaguar C-Type

On June 29th, 1956, the Federal Aid Highway Act was passed, providing a whopping $25 billion to build the Interstate Highway System. Suddenly, American cars needed to be optimized for high-speed travel on these new highways. This shift in focus led to a new era of car design, with sleeker, more aerodynamic models taking center stage.

1960 – 1965

Back in the 1960s, cars were like death traps on wheels. With barely any safety features, it’s no wonder the number of yearly car deaths was rising. But then came Ralph Nader and his book “Unsafe at Any Speed”. This powerful piece of literature led to the National Traffic and Motor Vehicle Safety Act of 1966, which required seat belts in all cars. As a result, the National Highway Traffic Safety Administration (NHTSA) was born in 1970 to enforce these safety regulations. In 1972, 5 mph bumpers became a requirement, leading to a complete overhaul in automotive design. But when everyone thought things were moving in the right direction, the US federal government implemented the National Maximum Speed Limit (NMSL) in 1974. This new law prohibited speed limits above 55 miles per hour, and it seemed like a steady change was on the horizon.

Chevrolet Corvette C2

During this period, scientists observed a spike in noise levels from fast cars. This prompted the development of roadways and car designs to reduce noise pollution. Despite these efforts, cars’ fuel economy was only around 14.3 mpg. The optimization of vehicles for drag reduction has been a hot topic for over a century. However, it wasn’t until the late 1960s that the racing community began to explore the benefits of aerodynamic downforce. The introduction of the Chaparral 2E in 1966 was a game-changer as it featured a large wing mounted on struts above the rear of the car. This design was soon adopted by the iconic Lotus 49B, driven by Jim Clark, which debuted at the 1967 Dutch Grand Prix. The addition of these rear wings resulted in an increase in cornering speeds and a significant improvement in lap times. This paved the way for further development of aerodynamics in racing, which continues today. It’s fascinating to see how these innovations have transformed the racing world.

Malaise Era – Early 1970s to mid-1980s

The automobile industry has seen many changes, but one significant era was the malaise era from 1973 to 1983. This decade characterized rapid highway growth, gas shortages, and an economic downturn. In response, the US government established the CAFE standard, which required automakers to improve their fleet’s fuel efficiency. Thanks to this standard, the average fuel economy of US cars doubled from 14.2 mpg in 1973 to 28.6 mpg in 1988.

In the late 70s and 80s, American-made cars had to meet fuel economy and safety regulations while alternative engines were experimented with. The Iranian Revolution in 1979 caused an energy crisis and reinforced the need for stricter fuel economy laws. Imported cars like Honda and Toyota began to dominate the market. By the 80s, all cars were required to have speedometers that highlighted 65 mph and wear seatbelts for safety.

Rolls Royce Corniche

This era also celebrated the American muscle cars. They were the kings of the road, with their roaring engines, sleek designs, and unmatched performance. Think of the legendary Ford Mustang, the iconic Chevrolet Camaro, and the evergreen Dodge Charger. Even after all these years, they continue to hold a special place in our hearts, reminding us of the golden era of American automobiles.

Era of American Muscle Cars

1985 – 2000

In the mid-1980s, car design took a turn towards sleekness. Cars began to feature slanted front ends, wrap-around headlights, and bubbly greenhouses, giving them a candy-like appearance that earned them the nickname “Jellybean.” European car manufacturers like Peugeot 405 and Audi 100 quickly adopted this trend, while the 1984 Ford Taurus was the first American car to embrace aerodynamics. As time passed, cars became increasingly streamlined and lost their hard angles. The CAFE standard for cars remained constant at 27.5 mpg until 2011. Notable cars that embraced the jellybean shape include the 1996 Ford Taurus, the 1998 Chrysler Concorde, and the 1993 Vauxhall Corsa.

Chrysler Concorde

Efficient car design with wind tunnel testing and CFD Simulation

Back in the day, car manufacturers had to resort to scale modeling to enhance their cars’ aerodynamic performance. Then, in the 1960s, new regulations for fuel economy and safety made it crucial to test cars for their aerodynamic drag. That’s when wind tunnels came into play. Interestingly, wind tunnels had already been used for aeronautical purposes for almost a century before they entered the automotive industry. Ford was the first to conduct an aerodynamic model test program in 1955 at the University of Detroit wind tunnel. Wind tunnels quickly became the go-to vehicle performance testing solution until computational fluid dynamics (CFD) emerged.

Automotive wind tunnel testing.

With the advent of electric computers, CFD simulations became possible. Initially, CFD simulations could only handle basic shapes (until the 1980s). But with advances in computer technology and turbulence theory, CFD can now simulate and design complex bodies such as engine compartments, wheels, and rearview mirrors. CFD simulations allow for multiple model design features to be tested, enabling designers to determine the optimal design.

Aeroacoustic simulation using Fidelity LES Solver.

The evolution of car design has been a thrilling ride, moving from a focus on horsepower to fuel efficiency measured in miles per gallon. With the advent of new technologies like electric and self-driving cars, it will be fascinating to observe the future of automotive design. Could a combination of AI and GPU-accelerated high-fidelity CFD simulation replace wind tunnel testing in the near future?