Volkswagen's Design and Development departments worked closely together from the earliest stages to define every detail of aerodynamics and achieve a Cd value of 0.23 - the best of the entire ID. family.
Volkswagen's family of all-electric vehicles is being expanded with a new model: the ID.7, whose high efficiency allows a range of up to 700 km (WLTP). This achievement is mainly related to two factors, which are the new drive generation and sophisticated aerodynamics.
The aerodynamically favourable basic form, low drag coefficient (Cd value) of 0.23 and frontal area of 2.46 m² are the result of close cooperation between the Design and Development departments.
The importance of shapes
With limousines like the ID.7, the body shape accounts for about 50% of the Cd value, while wheels and tires determine 30%. The remaining 20% is divided more or less equally between the underfloor and the grille air intakes, which serve to channel air to the radiators. The fact that the new ID.7 is the most aerodynamic model in the entire ID. family so far can be seen when looking at the silhouette of the car, which is nearly five meters long.
"When designing the ID.7, aerodynamics was a priority, more than for any other model. This can be seen in the low front end, the flowing transition into the bonnet and the fast windscreen. The coupé-like roof form and the tapering rear end are also designed for ideal aerodynamic performance", explains Volkswagen designer Daniel Scharfschwerdt.
Simulations and wind tunnel
To achieve such sophisticated aerodynamics, intensive work was carried out on the exterior design, underbody, wheels and other details was intense from the earliest stages of development and involved close collaboration between developers and designers.
"We strive for ideal solutions in an iterative process, which includes regular consultation between the Development and Design departments. Proceeding in small steps, we achieved very good results: we performed many computer simulations to calculate the flow, complementing them with tests in a wind tunnel", adds Stephan Lansmann, Project Engineer in charge of ID.7 aerodynamics.
The role of the underbody
The underbody of the Volkswagen ID.7 is almost completely closed. This is supplemented by newly developed wheel spoilers on the front wheels, which guide the air along the wheels under the vehicle with minimum turbulence.
Air curtains at the sides of the front bumper, on the other hand, direct the air around the vehicle front with minimum loss, while flared side sills prevent the air from flowing into the underbody area and shield the rear tire, preventing turbulence. Finally, airflow across the underbody is directed by a number of small spoilers and trim panels.
"On electric vehicles, the wheels make a greater contribution to good aerodynamics, we therefore focused on them in particular. The priority in designing the wheel rims was aerodynamics, along with brake cooling requirements. The result is a rather closed rim with particularly good aerodynamic properties", Lansmann resumes. The level of attention to detail was so high that flow simulations also looked at the tire contours, so that variants with less good aerodynamic properties were optimized early in the design process.
Much attention was also paid to the functional openings in the front end, through which air flows to the radiators. In the ID.7, the air flow is actively controlled by a radiator roller blind in order to reduce the drag. The electrically operated roller blind opens only when targeted cooling of the power units and battery is required. Finally, at the rear, the key elements for aerodynamic efficiency are the ideally shaped tailgate, the design of the diffuser and side separation edges.
Computer and clay models
The first part of the aerodynamic work was done with computer simulations. "In the first year of development the work is completely virtual, with updates about every two weeks. The car only goes to the wind tunnel when the design is stable, which can take up to a year and a half from the start of development", Lansmann concludes.
The process begins with the design team sharing Computer-Aided Design (CAD) data, after which processors calculate the air flow values, even for details such as flush-recessed door handles or rearview mirrors. In the wind tunnel work, however, life-size clay models of the Volkswagen ID.7 were used. Any changes or developments, for example to the rear end and separation edges, were transferred to the model using a milling cutter with millimeter precision.
The 3D printer
A 3D printer was also used to make the prototypes, thanks to which Stephan Lansmann's team was able to evaluate numerous variants, for example for the rearview mirrors, whose shapes have a great impact on aerodynamics. Through this process, both the lower and upper parts of the mirror housing, but also the base itself, were optimized to achieve a lower drag coefficient.
Thanks to this great attention to detail work, the Volkswagen ID.7 can boast a Cd of 0.23, which is the best drag coefficient of the entire all-electric Volkswagen ID. family.
Source: Volkswagen Newsroom
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