How to Build a FIA GT3 Car.
The FIA GT3 class of race car is the pinnacle of production sports car racing. Around the world, car companies take their most prestigious and expensive sports car models, strip them down to the bare frame, and tune them until they can do 200 km/hr for 24 hours straight. Car companies choose their top of the line, both for marketing and engineering reasons. For example, the Porsche 911 GT3R is derived from the Porsche 911 GT3 RS road car, which has an inherently light and stiff frame (on the account of being a 200,000+ dollar car) allows for Porsche to almost drop-in the chassis without a whole lot of modification work. The same goes for the Mercedes GT, BMW M4, Audi R8 and every other GT3 chassis. However, in 2024, Ford Performance brought an entirely new approach. Ford doesn’t exactly have a premier luxury sports car. Their best-known car is the Ford Mustang. Relatively affordable, powerful American muscle. However, Ford wanted to bring the Mustang to the world’s racetracks. Le Mans, Nürburgring, Daytona, and Long Beach. This is a rather difficult challenge, as the Mustang frame is not nearly stiff enough to handle the racetrack, while also simultaneously being far too heavy. Here, Ford Performance chose to do something special, which I was able to get a good look at during my time at the track.
Above is a picture of the rear suspension of the ROWE Racing BMW M4 GT3. Upon careful inspection, we can see that the rear of the production car is still very much there, with the non-load bearing parts being cut off and replaced with cosmetic lightweight composites to retain the classis BMW M4 shape. This Is not the same for the Ford Mustang GT3 though.
If you look carefully at the tube-frame encapsulating the engine, you can see that the frame comes together into nodes at all the places where the suspension is mounted. Here, the body structure now bears no load. The rear of the car is similar, but unfortunately I wasn’t able to take a picture. The only remains of the Mustang chassis, of which they are required to use as a base, is the center, which has been strengthened significantly as well. In essence, the Mustang GT3 is a car chimera, rather than a race-track Ford Mustang. I’m sure, to the marketing department, this open secret being widely known would be a major disaster. However, for the engineers, this is a boon. The car is significantly stiffer and lighter than it would otherwise be. This is ideal, as systems that flex significantly are difficult to control and manage and often have unexpected behavior in seemingly normal conditions. The Mercedes Formula 1 team learned this the heard way in 2022, where the chassis was not stiff enough, causing bending at the mid-rear of the car, which lead to oscillating behavior due to the way the aerodynamics worked.
Ford’s compromise has mostly worked out for them though, with the Mustang GT3 having won the 24 Hours of Daytona just this past year. The Ford Performance engineers are some of the best in the world, and having the chance to chat with them had to be one of the highlights of my time in Bonn. Their attention to small details that would make the car more drive-able was something that impressed me greatly. For example, when the drivers in the #6 car struggled with rear stability when lifting off of the throttle, the engineers immediately had the correct solution, changing the engine map of all things.
Ford’s program, despite perhaps not having the theoretically correct bones, has proven to be highly competitive, thanks to some clever engineering to meet the requirements of the regulating bodies, marketing departments, and competition demands. It was incredibly inspiring to be able to spend some in-garage time with members of their program.
Kirk N
