The Aerodynamics of a Porsche
Have you thought about what goes into the aerodynamics of your Porsche and how certain parts allow your car to adapt to your driving style? We're covering drag performance and vehicle handling and how they affect your Porsche's aerodynamics.
If you're looking for faster and more efficient handling, learn how Dundon has utilized Computational Fluid Dynamics to engineer parts scientifically proven to give you the competitive edge you crave both on the track and the road.
- How Aerodynamics Affect Performance
- Computational Fluid Dynamics
- How Different Performance Parts Affect Aerodynamics of a Porsche
- Putting it all Together: Harnessing the Power of Aerodynamics
How Aerodynamics Affect Performance
There are two main areas of aerodynamics affects the performance of a vehicle: drag and handling.
Drag
How exactly does drag affect the aerodynamics of a Porsche? Let’s break it down!
When the Porsche is rolling in a direction, the engine fights against the air and wind as it pushes or pulls the vehicle forward while braking or accelerating backward. This fight is referred to as Drag and is commonly measured using the drag coefficient. When a vehicle experiences more drag, the engine has to burn more fuel to move the vehicle.
As Porsche models’ drag coefficient is improved, through careful design, its fuel consumption is decreased, increasing straight-line performance such as 0-60mph acceleration times or ¼ mile drag race times.
Handling
The automobile designer does have to consider how to keep drag low and aerodynamic downforce high, as it’s the downforce (force created as the car moves through the air) that helps the cars ability to change direction (lateral acceleration) by manipulating the air around the vehicle to push the car into the ground more as the speed increases. Creating efficient, low drag downforce is what all aerodynamicists crave.
With Porsche 911 GT3’s and sports cars, in general, we want the car to be pushed more into the ground. Performance aerodynamic parts are generally tasked with reducing drag, creating additional low drag downforce and manipulating the front axle and rear axle amounts of downforce for the driving style and driver capability. Many times Porsche sides on reducing drag more so than adding downforce, this leaves an opportunity for us to add more performance to your car!
Computational Fluid Dynamics
Computational Fluid Dynamics (CFD) is a method of studying and modeling aerodynamics through sophisticated computer modeling. Why not test every part in a wind tunnel you ask?
Cost and complexity. Getting a Porsche GT3, or say a full-sized Boeing 747 airliner, for example, into a wind tunnel is costly and difficult. It’s a far better idea to do as much of that work as possible in a computer model that has the data from the model verified in a wind tunnel on a well-understood device (like a wing) in a systematic way. Trust but verify!
That three-dimensional space is called a flow field. In CFD, the flow field is broken down into discrete points with coordinate lines moving through those points to create a grid. That grid is then overlaid onto the body of the Porsche to simulate air moving over, under and around the car. The varying pressures and velocities of the air can be tracked at isolated parts along with the vehicle, creating a model that looks something like this.
On the 981 GT4 model below, the numbers refer to individual performance parts:
- Dive Planes
- Rear Diffusers with Flat Underbody Panel
- Front Splitter and Air Dam
- High Downforce Single Element Rear Wing
The model then creates completely numerical analyses of the aerodynamics of the body of the Porsche 911 GT both for the entire body or at isolated points along the body. Because there are many different discrete points being measured around the body, isolated parts of the Porsche can be tested to improve the aerodynamic capability of the whole vehicle.
This allows engineers to create multiple parts, set up an analysis (or run) and understand in a few hours or days how the designs will improve the aerodynamic performance of the vehicle. In the old days, designers would create a part, manufacture it, and then have to test its viability in a wind tunnel or run it on track to see if it was effective. CFD allows even small companies to design parts that are highly effective!
By utilizing the power of Computational Fluid Dynamics, engineers are able to create scientifically backed sports car performance parts to improve the Porsche GT car’s ability to cut through the air.
How Different Performance Parts Affect Aerodynamics of a porsche
Here's a breakdown of a few different performance parts for various Porsche models (models include: GT, GT3RS, Boxster, Cayman, etc.) and how they improve and tailor the aerodynamics.
Wings
Wings create additional downforce on the Porsche by applying the same logic as an airplane, but backward. Instead of having wings that lift the plane up into the air, the Porsche GT’s have a rear wing that pushes it into the road.
The velocity on the bottom side of the wing is higher than the top side which causes the pressure differential between the top and bottom surfaces. The wing also changes the direction of the overall airflow on the rear of the car from aiming downward to straight rearward/slightly up. This is a positive change and signifies the rear wing is working well with the entire car’s geometry.
One of our rear spoilers, the Carbon Bolt On Wing for the 991.1 and 991.2 GT3 adds much-needed downforce. When paired with our Single Dive Plans or Dual Dive Plans, it adds 400-lbs of downforce at 140 mph with minimal drag.
Dive Planes
Dive planes can serve a variety of purposes. While most people believe dive planes produce downforce by the airflow on the units themselves; a well-designed dive plane can do significantly more to increase the effectiveness.
A small part of the downforce created by the dive planes is from the forces on the surfaces of the dive planes themselves. The bottom side of the dive planes is lower pressure while the top side is higher pressure. This creates a downward force. This is not the full story, however.
The main way downforce is created with well-engineered Dive Planes / Canards is controlling airflow around the car. The Dive Planes are used to create a vortex that helps pull air out of the fender wells. This helps reduce lift on the body of the car. We have specific templates for the dive planes since location and placement are critical for maximum performance.
Splitters
Front splitters are very effective at producing frontend downforce without increasing drag. They do this by creating a large pressure delta between the top of the splitter and the bottom of it. Air pressure on top of the splitter is increased while the air pressure beneath the splitter is decreased resulting in major frontend downforce.
It also limits the airflow to the bottom of the car creating a low-pressure zone. Air builds up on the front of the car and on the splitter to add pressure.
Some aftermarket performance splitters are made from carbon fiber or aluminum, but our Bolt On Carbon Splitter Kit for the 981 GT4, 991.2 GT3, and GT3RS, and soon for 991.1 GT3 and GT3RS is made from carbon thermoplastic, which is considerably less brittle than carbon fiber and won’t bend and grab underneath the car like aluminum.
Diffusers
As a Porsche cuts through the air, the air initially is at a constant atmospheric speed, then accelerates under the car, and then rapidly returns to its normal constant speed once it has passed under the car. That moment when it returns to its normal speed creates a lot of drag on the vehicle, so diffusers are designed to help that transition.
Rear diffusers are extremely efficient downforce-producing and drag-reducing devices when designed properly. Rear diffusers ease the speed and pressure of air back to normalcy rather than a “suction point” being created, pulling the car backward.
Using a state of the art R&D process we created a functional and aesthetically pleasing 981 Cayman rear diffuser kit for optimal downforce efficiency.
Putting it all Together: Harnessing the Power of Aerodynamics
Hopefully, this little bit of background helped to understand how air flowing over the car can be harnessed to improve its performance. We want you to come away with an appreciation for both the complexity of the problem and how wind tunnel verified CFD analysis can allow small companies to design custom-tailored aerodynamic solutions that vastly improve the performance of your Porsche GT3, GT4 or frankly any car the methods are applied to.
If you’re looking to go faster and reach top speed on the track with your new Porsche GT3, enjoy your Sunday morning Canyon blasts with friends, or just add a fully engineered and tested “RSR” look to your GT4, {{cta('0b447b13-747e-459b-bc47-71438d00b3ce')}} to learn how Dundon Motorsports can help!