saw the M6 overtake many of GT LM and GTD cars under braking, with three cars being overtook at once in some cases at Daytona.
Chassis
For the chassis, it remains fairly conventional in the terms of a monocoque. The M6 runs a steel frame with a full Carbon Fiber outer body panels. This gives the car an astonishing weight of just only 1250Kg. Jens said “you could strap a V12 Formula 1 car engine to its roof, and it will still undercut the weight of its production siblings” which just goes to show that every ounce of this car is pure, with no excess fat.
The chassis provided a rigid foundation, which sees the M6 similar to where the Z4 left off, very rigid. It’s always been in BMW’s nature to run a well-engineered chassis and aerodynamics, which showed on the twisty inner section of Daytona.
Aerodynamics.
From the Z4, “the M6 is a major step in the right direction for the aerodynamics” exclaims Marquardt. While the Z4 was a draggy car, its ability to carry speed through corners was an ability could frustrate other marques. While the M6 is big, it’s still very efficient in the design BMW Motorsport has incorporated.
The front sees an all new splitter which is used for car balance. As the back sees a big rear wing, you need to balance the car upfront with a splitter being the perfect component to use. As the flow goes under, the low pressure pulls the splitter downwards thus giving you frontal downforce. The high pressure above the splitter will circulate of the bumper and trails to its outer edges, as well as go underneath the car. We know this from Bernoulli's principle of flow pressures.
What we want to have is lower pressure, faster-moving air below the car, and higher pressure, slower moving air above the car. The lower pressure side, when it happens to be under the car, contributes to reduced lift. When the lift is reduced sufficiently to the point where there is negative lift, there is net positive downforce.
The splitter itself does not actually create downforce. What the splitter does is that it increases the area over which high pressure can build up. The higher pressure there is above the splitter, the lower pressure is below the splitter, thus pulling the car towards the tarmac.
Mounted on the front bumper you can see standard GT aerodynamics in the terms of dive planes, where the BMW runs one either side. These small planes stick out to create an up-wash of high pressure. As the car brakes, these, along with the splitter keeps the front of the car straight and level, therefore adding in traction and grip for the front axle.
At the rear, BMW is running an all new rear wing, which they have changed the supports, main plane and gurney flap. The angle of attack on the main plane is quite aggressive, which will produce more downforce, as well as drag. The gurney will be used to stall the flow under the wing, while not having much effect on the top. The air then exits the wing near enough the same point it enters it, almost the same thickness, albeit more turbulent.
In other words, the device basically operates by increasing pressure on the pressure side of the wing, decreasing pressure on the suction side, and helping the boundary layer flow stay attached all the way to the trailing edge on the suction side of the aerofoil.
At the very rear, BMW is running all new diffuser too, which is bigger and runs more slats. The diffuser is a great wat to speed up the low pressure under the car, which is squeezed into the car via the throat of the diffuser. As the air expands, it speeds up. The low pressure is what produces the downforce here also.
BMW really went to town with its new customer GT car. The Z4 was the perfect all-rounder, so the M6 has a lot to beat. BMW are offering free technical support to its customers too so that BMW Motorsport can see the M6 be successful. While it could only achieve a 5th place at Daytona BoP really did hamper the BMW's top end speed while Corvette seemed to not have been so affected. This is not the car but IMSA rules. Over the course, the race, the downforce, and braking ability weren't enough to rival Corvette or Porsche.
IMSA is currently undergoing its BoP for Sebring, which should see a fairer balance of the both GT LM and GTD cars. Where we should see the BMW shine, something the Z4 did so well.