How Koenigsegg Revolutionized the Transmission with the Direct Drive System

If you are a fan of hypercars, you probably know that Koenigsegg is one of the most innovative and ambitious manufacturers in the world. The Swedish company has been breaking records and pushing the boundaries of engineering with its creations, such as the Agera, the One:1, the Jesko, and the Gemera. But perhaps the most radical and impressive invention by Koenigsegg is the Direct Drive system, or KDD, that is used in the Regera, the world’s first “megacar”.

The KDD is a patent-pending technology that replaces the traditional transmission with a hydraulic coupling and three electric motors. This means that the Regera has no gearbox, no clutch, no differential, and no fixed gear ratios. Instead, it relies on a direct connection between the engine and the rear axle, with the electric motors providing additional torque and power. The result is a smooth, seamless, and efficient acceleration from 0 to 400 km/h in less than 20 seconds.

How does the KDD work?

The KDD consists of four main components: the battery, the electric motor/starter, the engine, and the hydraulic coupling.

• The battery is a 620 V 9.27 kWh unit that sits between the two occupants and allows the car to run on pure electric mode for up to 50 km. The battery also supplies power to the electric motors and can be recharged by the engine or by a plug-in charger.
• The electric motor/starter is a 160 kW (~215 hp) motor that mounts up to the engine crank and acts as a starter motor and a generator. It also provides additional torque to the crank, especially at low speeds, and helps to smooth out the power delivery.
• The engine is a 5.0-litre twin-turbocharged V8 engine that produces 820 kW (~1100 hp) and 1280 Nm (944 lb-ft) of torque. The engine has a desirable torque curve, producing 1000 Nm (738 lb-ft) or more from 2700 to 6170 rpm. The engine reaches its peak power at 7800 rpm and has a redline at 8250 rpm.
• The hydraulic coupling is a device that uses a fluid to transmit mechanical power. It has the ability to open and close, meaning that the output shaft can be connected or disconnected from the power sent from the engine. The hydraulic coupling acts like a torque converter, but without the lock-up function. It allows the engine to spin freely at low speeds, while transferring power to the wheels at higher speeds.

The KDD also features two driveshaft-mounted electric motors, one for each rear wheel. These motors produce 180 kW each (~240 hp) and are responsible for the initial acceleration from a standstill. They also provide torque vectoring and regenerative braking.

The process of reaching the top speed of 410 km/h with the KDD is as follows:

1. The two electric motors on the rear axle start the acceleration, drawing power from the battery. The hydraulic coupling is open at this stage, so the engine can charge the battery, if necessary but does not provide any power to the wheels. This is because the car is traction limited at low speeds, and adding more power would only cause wheel spin.
2. As the speed increases, the hydraulic coupling starts to close gradually, allowing the engine to join the party. The electric motor/starter also adds torque to the crank, boosting the engine performance. The electric motors on the rear axle continue to provide power and torque vectoring, ensuring optimal traction and stability.
3. At around 150 km/h, the hydraulic coupling is fully closed, and the engine is directly connected to the rear axle. The final drive ratio is 2.85:1, which means that the engine speed is proportional to the wheel speed. The electric motors on the rear axle still assist with power and torque vectoring, but their contribution decreases as the speed increases.
4. At around 250 km/h, the electric motors on the rear axle are switched off, and the car relies solely on the engine power. The electric motor/starter also stops providing torque to the crank, and acts as a generator instead, recharging the battery. The engine continues to accelerate until it reaches its peak power at 7800 rpm, corresponding to the top speed of 410 km/h.

What are the benefits of the KDD?

The KDD offers several advantages over a conventional transmission, such as:

• Reduced weight and complexity: The KDD eliminates the need for a gearbox, a clutch, a differential, and multiple gear ratios, which reduces the weight and the number of moving parts in the powertrain. The KDD weighs only 90 kg, compared to 140 kg for a typical dual-clutch transmission. This also improves the packaging and the center of gravity of the car.
• Increased efficiency and performance: The KDD minimizes the power losses and the parasitic drag that are associated with a conventional transmission. The KDD also optimizes the power delivery and the torque distribution, using the electric motors to fill in the gaps and enhance the engine performance. The KDD enables the Regera to achieve a combined output of 1100 kW (~1500 hp) and 2000 Nm (1475 lb-ft) of torque, making it one of the most powerful and fastest cars in the world.
• Improved driving experience: The KDD provides a smooth, seamless, and effortless acceleration, without any gear changes or interruptions. The driver does not need to worry about shifting gears, clutching, or rev matching, as the KDD does everything automatically and intelligently. The driver can also choose between different driving modes, such as electric, hybrid, or sport, depending on the preference and the situation.

Conclusion

The KDD is a revolutionary technology that challenges the conventional wisdom and the status quo of the transmission design. It is a testament to the ingenuity and the ambition of Koenigsegg and its engineering team, who have created a unique and innovative solution that delivers unparalleled performance and efficiency. The KDD is not only a game-changer for the Regera, but also a potential inspiration for the future of the automotive industry.