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GTM Aerodynamic Testing November 9, 2005 |
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Langley Air Force Base, Virginia: With three years of work behind us, the Factory Five engineering and GTM development team traveled to Langley Air Force base in Virginia to perform aerodynamic testing and analysis on the GTM using the Langley Full Scale Tunnel (LFST). The culmination of our design work in-house and our best race experience would mean nothing without verifying the design in real life, at speed in the tunnel.
The wind tunnel at Langley is MASSIVE. It is the largest currently operating wind tunnel in the world and has been used to test a wide range of racecars from NASCAR stock cars to Grand AM and ALMS prototypes. |
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Since the test platform is located two floors above the ground level (!) the car was hoisted up to this raised surface. After securing the car to the platform it was time to make an initial run.
Team members Jim Schenck, Mike Pisani, and Eric Jacobs assisted the staff at the facility in preparing the test car. The car we used was prototype #3 that had just returned from the SEMA show earlier in the week. Baseline data was taken on the car in a pure street configuration at 4-1/2” of ride height.
With the initial run complete, testing began on a variety of configurations involving changing the functional parts of the car (front splitters, hood cutout shapes, rear diffuser angles, rear wings, internal ducting changes and small ride height alterations).
Following that data we observed air flow patterns over the contours of the body and internal ducting using a white smoke trail generated inside the funnel. |
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The results were exciting as they showed that the car performed the way we hoped it would. The car has a very good aerodynamic balance and no changes to the body shape are necessary (Thankfully since we all love the current shape).
We decided on a final rear diffuser angle that optimized downforce, f/r balance and drag. A significant change was seen by moderating the size of the apertures on the front hood.
We know we can generate better numbers by lowering the ride height to a race set-up and using radically different front splitter and rear wing configurations, but we wanted to optimize the street configuration first. |
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The most important fact that we established was that the GTM shape nets a safe aerodynamic profile, capable of running high speeds and staying firmly planted to the road.
Special thanks to Eric Koster and his LFST team of engineers who advised us in our testing, and for giving us the opportunity to use their awesome facility.
Comparison data (source Road & Track Magazine):
2004 Porsche GT 343 lbs. DOWNFORCE @ 150 mph 1999 Ferrari 360 Modena 294 lbs. DOWNFORCE @ 150 mph 2005 Factory Five GTM 333 lbs. DOWNFORCE @ 150 mph
Note: Almost all production cars on the road today produce lift. |
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