Hirsch on Aerodynamics

Here’s a little more Hirsch material.
Hirsch Performance have just released a new aerodynamics package for the 2009 Hirsch Performance edition cars that will be sold in various markets aroud the world. These are Hirsch’s own notes about the new package and they’re good for not only finding out about Hirsch products, but also the importance of aerodynamics and the role played by various parts in the package.
Click any of the photos to enlarge.
Improving the aerodynamics of the current Saab 9-3 was a real challenge, since the car has excellent aerodynamics already from the factory.
However, for this project Hirsch Performance enjoyed the co-operation and support of Saab’s master aerodynamicist Håkan Danielsson and his team, as well as renowned designer Taras Czornyj from Mutations AB, whose combined experience made it possible to develop a truly exciting aerodynamics package.
The final product range reaches from front splitter to an exclusive – limited edition – carbon fiber body kit for the SAAB 9-3 Performance special edition car.
Form follows function – Design process
The aerodynamics package was designed as a complete set of modifications to improve stability and reduce drag. In addition to the functional benefits, the aerodynamic modifications should also contribute to the car’s dynamic appearance.
During the entire development process, close co-operation between design, aerodynamics and engineering ensure that the end result creates the best possible experience, both when viewing the car from the outside and when driving at high speeds.

The design process started with the sketching phase, trying to get the most distinctive look possible while still integrating with the shape of the original car.
The sketches were then interpreted in clay, to ensure that the shape of each component looks good from all angles.
Once the basic clay design had been approved, the car was scanned using a 3D-Scanner, and the surfaces translated into 3D computer models.
Aerodynamic optimization – Wind tunnel test
Based on the computer models, aerodynamic test parts were produced and specially prepared so that minor adjustments could be made quickly during the wind tunnel testing.
Front splitters were added to reduce air flow under the car and in front of the wheels, thus creating down force. A larger front spoiler was integrated with the lower mesh grille, further reducing air flow under the car while also increasing the cooling air flow for the intercooler. Side skirts were added to reduce wake behind the wheels and keep the air flow under the car from leaking out. In the rear, a diffuser was added under the bumper to direct the air flow slightly upwards, thus reducing the wake behind the car while also improving rear stability.
For the Convertible and SportSedan, enlarged bootlid spoilers also help improve rear stability.
Perhaps the most interesting component, however, is the roof spoiler for the SportCombi, where a Saab innovation from 1961 was put to use again in a modernised form: the air slicer. The top surface of the air-slicing roof spoiler directs the airflow upwards, generating improved rear stability. In addition, an air slot directs a small portion of the airflow down onto the rear screen, thus reversing the semi-stationary vortex behind the car and thereby reducing the wake and the associated aerodynamic drag, while also helping to keep the rear screen clean.
This design was extensively tweaked and tested in the MIRA wind tunnel, to create an optimal combination of drag and stability.
Safety first – Homologation
Once both the design and aerodynamics targets were met, homologation prototypes were produced. All prototypes were installed on cars and sent to RDW in the Netherlands for homologation. At RDW, the parts were examined to verify that they will not influence the safety of the car or the safety of pedestrians in case of a collision.
All aerodynamic parts have successfully passed the homologation tests, and are included in the latest Saab 9-3 whole vehicle type approval, and can therefore be installed in all markets.
Carbon fibre body kit
Hand laminated in high quality carbon fibre and lacquered with a UV-resistant high gloss coating.
The limited edition complete carbon fibre body kit is available exclusively for the Aero trim level. As a sign of authenticity, Hirsch Performance logotypes in aluminium are laminated into the rear side skirt extensions.
The kit is available for all body types; SportSedan, SportCombi and Convertible, and consists of 8 pieces: Front splitters, side skirt extensions front and rear, and rear bumper extensions.
The front splitters direct airflow away from the front wheels. The skirt extensions help separate the airflow under the car from the airflow on the sides, and also reduce the wake behind the wheels, thus reducing lift and aerodynamic drag.
Front splitters for Aero and Vector
Available for both the 9-3 Aero and Vector/Linear front bumpers, front corner splitters were developed to help direct airflow away from the front wheels. The front splitters generate downforce at higher speeds and help to reduce the aerodynamic drag.
The Aero front splitters are available in two versions; hand laminated carbon fibre, as part of the carbon fibre body kit, and as individual components in high-quality PUR.
The Vector/Linear front splitters are available only in high-quality PUR.
The PUR front splitters are delivered primed, and can be painted – either as the designer intended in matte black – or in body colour.
Bootlid spoilers for SportSedan and Convertible
Rear lift forces cause instability at high speeds on sedans and convertibles, and the perfect solution to address this issue is to add a bootlid spoiler that raises the airflow and provides a clear separation point for an optimized wake behind the car.
The Hirsch Performance bootlid spoilers are optimized primarily to improve high speed stability, and therefore they are slightly larger and have a slightly steeper rake to produce optimal aerodynamic results.
The styling is functional and minimalistic with no grooves or decorations. The spoilers are delivered primed, and can be painted – either as the designer intended in two tone with matte black underside and body colour on top – or completely in body colour.
Roof spoiler for SportCombi
Most wing-type roof spoilers trade off aerodynamic drag to achieve better rear stability. The new Hirsch Performance roof spoiler for the Saab 9-3 SportCombi is unique in that through rigorous wind tunnel testing, it was possible to achieve both a reduced drag and improved stability, while in addition keeping the rear screen clean!
The styling continues the smoothly curved wing design theme established with the Hirsch Performance 9-5 roof spoiler.
The roof spoiler is delivered primed, and can be painted – either as the designer intended in two tone with matte black underside and body colour on top – or completely in body colour.
The kit includes brake light extension cables to be used with the existing brake light, which is positioned in the spoiler, and an extension hose and nozzle for the rear screen washer.
Mesh grill
Improved cooling air flow helps keep the engine temperature under control, and improves the performance of the intercooler. Therefore, the Hirsch Performance mesh grill kit has large openings that allow maximum airflow. However, the outer upper grills remains closed like on the original grill, to achieve lower aerodynamic drag, and ensure that splashing water does not enter the engine’s air intake snorkel.
The upper 3-piece grill is available separately, and fits Aero, Vector and Linear cars. The lower grill with integrated spoiler is available only for the Aero trim level.
The mesh grill is produced in injection-molded high-quality UV-stablized ABS, to ensure that the matte black finish remains beautiful for many years, with the best possible resistance against chipping and harsh cleaning agents. As a sign of authenticity, a Hirsch Performance emplem in matte chrome that matches the original grill frame is integrated in the upper grill.
Rear diffuser
With the installation of a diffuser under the rear bumper, the airflow under the car is stabilized and directed upwards, thus improving stability and reducing the wake behind the car.
The Hirsch Performance diffuser features two round openings for either the Saab Original dual exhaust or the Hirsch Performance dual exhaust. The diffuser has been specially designed to fit both the longer SportCombi and the shorter SportSedan/Convertible bumpers, as well as both the Aero trim level and Vector/Linear trim levels. The diffuser is compatible with the Saab Original towing hooks, and features markings for the required cut-out on the inside of the diffuser.
The diffuser is delivered in matte black high-quality UV-stablized ABS. The kit includes rivets for installation. The bumper reflectors (not included in the kit) are moved over from the original bumpers to the diffuser.