The car runs through the air every moment. The faster the car, the stronger the resistance of the air it faces - the air hitting the vehicle flows more intensely. The interaction between the car and the air while driving greatly affects the car's driving performance, fuel economy, driving stability, and noise. This is why all car manufacturers put a lot of effort into aerodynamics studies that deal with car movement and airflow.
Aerodynamics is more important for many electric vehicles (EVs). If you increase the battery capacity, driving distance also increases, but so would the price and weight. In other words, in order to make an EV that runs longer with the same battery size, aerodynamics becomes the key to its practicality.
The IONIQ 5 is Hyundai Motor Company's first EV-exclusive model, and it symbolizes the beginning of a journey toward its agenda, 'Progress electrified for connected living'. In order to create an innovative experience worthy of the electric vehicle era and a spacious space optimized for a passenger-specific lifestyle, IONIQ 5 has a long 3,000mm wheelbase (distance between the front and rear wheel) with the battery placed at the bottom of the body. In addition, its tall SUV style maximizes cabin space by shortening the front and rear overhangs - distance from the front (rear) axis to the front (rear) of the vehicle.
However, securing the SUV style - the practicality of the cabin space, the expansion of the cargo space, and the high rear glass - for the sake of the convenience of the rear seat occupants, is never good for aerodynamics. In other words, practicality and aerodynamics often contradict each other.
In order to overcome disadvantages, Hyundai Motor Company has undergone many tests with great care with all departments related to aerodynamic performance for a long time. Based on a design optimized for aerodynamics, a functional design was applied to the IONIQ 5 to offset the downsides and to improve the design completeness. Aerodynamic performance is considered in various areas such as the rear spoiler, which is a key element of aerodynamic performance (the ability to handle the interaction between the car and air), the intelligent airflow controller (Active Air Flap, referred to as AAF), the wheel, and the undercover. A streamlined clamshell bonnet with a low seat, a gently inclined A-pillar, and the lowest ground clearance (height from the road surface to the body) compared to a typical crossover are also some of the aerodynamic elements of the IONIQ 5.
As a result, the drag coefficient of the IONIQ 5 was 0.288, which reduced the air resistance by about 11% to 18% compared to a car with an internal combustion engine of the same class (drag coefficient: 0.32 to 0.34). This is similar to the drag coefficient (0.28~0.31) of other electric SUVs, and it makes the excellent competitiveness of IONIQ 5. Let's take a look at the aerodynamic elements of IONIQ 5, from its design development process.
IONIQ 5 inherits the design heritage of Hyundai's first unique model, Pony, while embodying Hyundai's vision for future mobility. This is why we can see the design element of Pony from the silhouette of IONIQ 5, which minimizes the parting line (the dividing line that splits each surface).
However, there are also some aerodynamic disadvantages, such as the angle of the rear glass tilted at an angle. In general, from the aerodynamics perspective, it is more effective to use the steeper rear window for SUVs, and the rear glass with a gentle slope for sedans. And for hatchback models such as the Pony, it becomes difficult to control the flow of air, thus increasing the resistance. The designers and engineers of the IONIQ 5 have spent a long time developing a rear spoiler that complements the drawbacks of the rear glass angle for optimal aerodynamic performance, which is important for electric vehicles while implementing a design that connects the past, present, and future.
The rear spoiler is a key component in a vehicle's aerodynamic design. When the car is running, air flows all the way to the left and right, and up and down the car body. At this time, the rear spoiler reduces the force that lifts the car due to the air under the car body. At the same time, it improves driving stability by minimizing the eddy currents (vortex) that the air that has passed over the vehicle body and formed at the rear of the vehicle. The technology to reduce the lift is often applied to high-performance cars or race cars running at high speed, and the rear spoiler of a general passenger car is mostly to increase driving stability and fuel economy by adjusting the vortex of the air. For this reason, fine tuning such as the shape and angle of the rear spoiler is required based on the concept of the car.
IONIQ 5 has enough downforce (the force to press the vehicle body from top to bottom), which improves driving stability thanks to the weight of the PE system, such as batteries and electric motors, as well as the shape with a gentle roofline. Accordingly, a rear spoiler was developed primarily to reducing air resistance. The rear spoiler of the IONIQ 5 is made with an optimal aerodynamic design through a development process that is delicately adjusted at 0.1° intervals. Clogging the area next to the rear spoiler also plays an effective role in controlling airflow and reducing air resistance.
In an internal combustion engine car, the air is passed through a radiator grill to effectively cool the engine heat generated while driving. Electric vehicles also need cooling because electric motors and batteries generate a lot of heat. Based on Hyundai Motor Group's electric vehicle platform E-GMP (Electric-Global Modular Platform), IONIQ 5 is cooled by spraying oil for cooling and lubricating directly to the internal coil, rather than the conventional method where a cooling water line was installed outside the electric motor - and such a system indeed improved the performance. Reduced size and weight by integrating an electric motor, inverter, and reducer is a new feature of the IONIQ 5 PE system.
One of the main components of cooling the IONIQ 5's PE system is the Active Air Flap System (AAF). The existing AAF was developed to reduce the cooling resistance that occurs when cooling the engine through the radiator grill in an internal combustion locomotive, and it was a concept to reduce the resistance by opening and closing the flap (partition) whenever it requires cooling.
The external AAF applied to the IONIQ 5 has a high cooling resistance reduction efficiency by reducing the step difference from the front bumper surface compared to the general AAF, and when the grille is closed to reduce air resistance, it integrates with the bumper to make a simpler look. The difference in the drag coefficient that occurs when the AAF is opened and closed is about 0.013, which increases the range by about 7.3 km for each charging.
One of the factors affecting the range of an electric vehicle is the tire. Tires are the only parts that connect the car and the road surface, and rolling resistance varies depending on the shape and material, which has a great influence on the fuel economy of the car. The rolling resistance of the tire can be reduced by various arrangements of the tire or the size and shape of the wheel. IONIQ 5 is equipped with 235/55R 19-inch or 255/45R 20-inch tires, and both wheels minimize the open area of the wheel and they all have a flat front surface for better aerodynamic performance.
In addition, the amount of air hitting the tires while driving is minimized by preventing the tires from protruding outside the vehicle body - when viewed from the front. In addition, in order to minimize the resistance generated when the wheel rotates at high speed, the gap between the tire and the wheel is reduced, and the air generated along the tire surface gets to escape smoothly.
The Digital Side Mirror (DSM), which was first applied to IONIQ 5, is also for optimal aerodynamic performance. The air resistance generated while driving increases in proportion to the front area of the vehicle, and the side mirrors protruding from the sides of the vehicle increase the air resistance. For this reason, automakers reduce the air resistance by reducing the size of the side mirrors or making them thinner. IONIQ 5's DSM replaces the side mirrors with a camera, reducing air resistance and providing a clear rear view even in bad weather such as during the night or heavy rain.
In general, the impact of the shape of the upper and lower parts of the vehicle on the aerodynamic performance is said to be 45% and 35%, respectively. An electric vehicle with a flat battery installed under the body has a faster airflow under the body than an internal combustion locomotive. For this reason, if this could guide the airflow introduced through the front lower parts smoothly to the rear end of the vehicle body, it would increase the efficiency by reducing air resistance.
To maximize the advantages of an electric vehicle with a flat floor, IONIQ 5 has an undercover installed in the front and rear areas of the battery to meticulously fill the gaps that may catch air. In addition, the undercover was applied to the rear member where the rear suspension and electric motor are mounted, so that air can escape to the rear of the vehicle body. The battery rear undercover and rear member undercover are the first parts applied by Hyundai, and this could be the result of an innovative idea suitable for EVs, even the parts that are not seen from outside.
IONIQ 5 is attracting attention for its new high-tech specifications and spacious and usable interior space. The aerodynamic design with the performance of a regular sedan without compromising SUV style and space practicality will make the IONIQ 5 even more valuable. This is why IONIQ 5, full of various charms, is about to open the new era of electric vehicles.
HMG Journal Operation Teamgroup@hyundai.com
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