Aerodynamics at Mercedes-Benz: A History

Aerodynamics at Mercedes-Benz: history

An elegant front section, shaped along aerodynamic efficiency lines, large glazed surfaces and gullwing doors are the visually conspicuous features of the world-record-setting C 111-III experimental car.

• Inspired by aircraft construction: early aerodynamic optimisations of cars
• Records in series production: ancestry to the CLA with EQ Technology
• Aero-Champions: concept vehicles and technology platforms such as the VISION EQXX

More than 100 years ago, aerodynamics first came into the focus of science - but it was not until after the second oil crisis about 45 years ago that it was given high priority in vehicle development. The first passenger cars were derived from the carriage. Also because of the low possible speeds, aerodynamic considerations played no major role. Even the first “real” cars of the Mercedes brand from 1901 struggled against the headwind in a jagged manner. For example, the Mercedes Simplex from 1902 had a frontal area of around 3 m², and its C_dvalue of 1.05 meant that the wind encountered almost ten times as much resistance as in a modern passenger car.

Shortly after the First World War, the experts began to deal with the aerodynamics of automobiles. Aircraft designer Eduard Rumpler (1872-1940) presented his teardrop car in 1921, which with its narrow body not only addressed the question of the frontal area (2.4 m²), but with its teardrop shape minimised the turbulence at the front and in the wake. The result looked unusual, but with a C_d value of 0.28 and an air resistance of 0.67 m², it set a clear signal.

Paul Jaray (1889-1974), the other “father of streamlining”, also came from the aviation industry. Also in 1921, he applied for a patent that still reads like instructions for building a modern car body: “The lower part of the body has the shape of a half-streamlined body and covers the chassis with the wheels, the engine compartment and the passenger compartment. The underside is flat and runs parallel to the floor surface.” For the first time, the wheels were no longer free, but were integrated into the body, and the fastback minimised turbulence at the rear. Because conventional drive technology fit under Jaray's body shape, some car manufacturers built vehicles according to his principle, including Mercedes-Benz: in 1935, a correspondingly shaped prototype was created.

The biggest disadvantage of Jaray's streamline was the long trailing rear - a “dead” space. The solution was found in the 1930s by Wunibald Kamm (1893-1966), the first professor of automotive engineering at the Technical University of Stuttgart and in 1930 founder of the private and non-profit Research Institute for Automotive Engineering and Vehicle Engines Stuttgart (FKFS). Kamm sharply cut off the streamlined rear and developed the prototype of an aerodynamically innovative passenger car with the K-Wagen from 1938 to 1941. The term “Kamm-back” for the sharp trailing edge is still a term today. The K3 car was based on a Mercedes‑Benz 170 V and, with a frontal area of 2.1 m², was characterised by a C_d value of 0.23, which was measured in the model wind tunnel at the time.

Increasing prosperity and falling gasoline prices in the 1950s pushed the effort to reduce driving resistance into the background. It was not until the second oil crisis in 1980 that attention was turned back to minimizing consumption and air resistance. The production cars from Mercedes‑Benz therefore repeatedly set standards in terms of aerodynamics: Examples of this are the S‑Class of the 126 series presented in 1979 with a C_d value of 0.36, the sedans of the E‑Class 124 series introduced in 1984 with C_d 0.29, or the S‑Class sedan (W 220) presented in 1998 with a C_d value of 0.27. With a C_d value of 0.22 and a frontal area of 2.19 m², the CLA (W 117) achieved the lowest air resistance of all production vehicles worldwide in 2013 (ditto the A‑Class sedan in 2018 and the S‑Class (223 series) in 2020). Most recently, the EQS reached for this title in 2021. With a C_d value from 0.20, the electric sedan is the most aerodynamic production car in the world.

Ahead of their time: record cars, streamlined cars, and concept vehicles

Aerodynamically-perfected racing and record cars also have a long tradition at Mercedes‑Benz. The Mercedes‑Benz W 25 record car of the 1936 season has a chassis with a full streamlined body for the first time. In the wind tunnel of the Friedrichshafen Zeppelin Works, the experts analyse and optimised the body in terms of flow technology. The result: a C_d value of 0.24, a speed world record, and three international class records. Rudolf Caracciola achieves a top speed of 372.1 km/h with the 419 kW (570 hp) record car.

The follow-up project, the Mercedes‑Benz W 125 record car, set the speed world record on public roads that is still valid today on January 28, 1938: Rudolf Caracciola reached a speed of 432.7 km/h. The record version of the Silver Arrow W 125 is perfectly prepared for its special purpose in the wind tunnel of the German Research Institute for Aviation in Berlin-Adlershof. The flat, fully clad body with a wedge-shaped rear reaches a sensational C_dvalue of 0.16. This also includes a radically reduced air intake at the front.

However, the aerodynamic findings are not only implemented for record-breaking journeys, but also on the road. The Mercedes‑Benz 540 K Streamliner built in 1938 crowns the development of aerodynamically optimised Mercedes‑Benz vehicles in the 1930s. With the flowing lines and low silhouette of its aluminium body, the minimised sources of interference on the surface, and the clad underbody, the Streamliner exemplifies the findings of research - it has a remarkably low drag coefficient of C_d 0.36.

The streamline of the Silver Arrows came back into the focus of the world public in 1954 with the completely newly developed W 196 R racing car. The aerodynamically optimised streamline version was built first for the 1954 season because the opening race in Reims/France allowed very high speeds. A second variant with free-standing wheels followed shortly thereafter. The racing comeback of Mercedes‑Benz ended spectacularly: Juan Manuel Fangio and Karl Kling achieved a double victory. With the improved version of the Streamliner, Fangio also won the 1955 Italian Grand Prix.

From 1969, Mercedes‑Benz built a series of experimental and record vehicles with the internal designation C 111. The C 111-III diesel record car from 1978 was consistently aerodynamically optimised. The vehicle is narrower than its predecessors, has more wheelbase, full fairing of the wheels, and a long trailing rear. In this way, the C_d value of the C 111 was reduced to 0.18. During record runs in Nardò, the Streamliner reached speeds of over 300 km/h. The nine world records of the C 111-III also include the one over 1,000 miles (1,609 km) with an average speed of 319 km/h.

Strictly speaking, the Concept IAA (2015) embodies two cars in one: a four-door coupé with a fascinating design on the one hand and an aerodynamics world record holder with a C_dvalue of 0.19 on the other. In addition, from 80 km/h, the study automatically switches from design mode to aerodynamics mode and changes its shape through numerous active aerodynamics measures: eight segments extend from the rear and lengthen it; extendable front flaps in the front bumper improve the flow around the bow and the front wheel arches; the active rims change their concavity; and the fin in the front bumper moves backwards, optimising the flow on the underbody.

With a C_d value of 0,17^[1] the VISION EQXX (2022) offers the wind even less air resistance than an American Football. The technology platform owes its outstanding C_d value to the streamlined basic shape, the innovative, aerodynamically neutral cooling plate in the underbody, and the elaborate integration of passive and active aero elements into the body.

As part of the CONCEPT AMG GT XX technology program, research was conducted into a fundamentally new technology: “Aerodynamics by wire”. For the first time, the research team was able to use an electric plasma actuator to create a targeted flow separation on a body curve at the rear. Normally, this requires a physical, geometric spoiler lip on the outside of the vehicle. This highly innovative solution reduces air resistance, improves aero performance, and enables completely new design freedom.