If you’re anything like me, you would have become weak at the knees when the Bugatti Chiron was unveiled at the 2016 Geneva motor show.
That knee weakness then turned to hot flushes when the wraps were taken off the Koenigsegg Regera.
While it’s not as quick as the Chiron to 100km/h (a little over 2.8 seconds v. 2.5s), the limitation of being rear-wheel drive wears off very quickly as it races to 400km/h from standstill in around 20 seconds.
Incredibly, it does all of this without a gearbox. There’s no dual-clutch, there’s no CVT, no stepped gears as we know them. How does it work? We’ve broken it down below to give you an idea.
To put all of this into perspective, we need to understand the core components of the system. The following elements are all involved in driving the Regera:
These elements combined offer a power output of over 1100kW (that’s 1.1MW of power…! To put that into perspective, it’s enough peak power to run the CarAdvice office with 15 employees 22 times over) and in excess of 2000Nm of torque.
At this point, you may be wondering why all cars don’t simply have one gear. Think of it this way — have you ever tried to pedal your bicycle in a low gear? It’s easy to start with, but progressively becomes harder to gain speed. Likewise, if you start in a higher gear it’s hard to begin with, but progressively becomes easier. It’s the same story with a car. Selecting a high gear or low gear would effectively limit movement, which is why almost all cars on the road have some form of stepped gears.
How does Koenigsegg overcome this in the Regera? The company does it by using a combination of the electric motors and its internal combustion engine, along with a hydraulic coupling between the engine and driveline. We’ve broken it down into three sections below — at idle, from 0-48km/h and from 48km/h to 400km/h:
One of the three electric motors (the crank mounted one) is used to power the starter motor and provide additional torque to the crank in situations where the engine is at low revolution speeds. The engine can also be used to charge the 620V, 9.27kWh battery system too via this electric motor.
At this point, when the car isn’t moving, the engine uses fuel to sit idle and the first electric motor uses power to run the starter motor when required.
When the driver selects ‘Drive’, the vehicle enters the next stage of motion that occurs between 0-48km/h.
From 0 – 48km/h (0 – 30mph):
It’s at this point that the whole system begins working. When the vehicle is in its ‘Drive’ mode, the two wheel-mounted electric motors begin supplying torque to the rear wheels individually and via an electronic torque vectoring system.
At this point, the internal combustion engine is still effectively doing nothing to assist the drive. The hydraulic coupling remains open, but starts closing gradually as speed increases to 48km/h, providing a ‘slipping’ effect.
These two wheel-mounted electric motors are quite unique. They are produced by a company called YASA Motors (Yokeless and Segmented Armature) and offer a direct drive element via axial flux motors. That means that the driveshaft can run through the centre of the electric motor, as opposed to the electric motor interacting with the driveshaft via a set of gears.
From 48km/h to 400km/h:
This is where the fun starts. Between 0 and 48km/h, the hydraulic coupling continues ‘slipping’, in a similar fashion to a torque converter. While details are scarce, it’s understood that in this application a chamber filled with fluid (normally an oil) contains an impeller on a shaft from the engine and a reactor attached to a shaft on the drive shaft. These two have no points of contact in their initial phase of slipping (at low speeds).
Oil inside the chamber is then used to transfer torque between the impeller and reactor, which drives the opposing shaft and provides torque to the wheels.
Normally there is no direct connection between these two shafts in a hydraulic housing — torque is transferred by the fluids inside the chamber.
As the engine revolutions begin increasing, the hydraulic coupling begins to close until it reaches a point where it is fully locked up by virtue of a clutch, providing direct and uninterrupted drive to the wheels.
The point at which it’s fully locked up, which is around the 50km/h marker, the engine revolutions are proportional to the vehicle’s speed.
So that means that it’s theoretical top speed will occur at around 8250rpm (the engine’s redline), which equates to around 400km/h, given the final drive ratio of 2.85.
Why bother with no traditional gearbox?
The main reason is weight. By eliminating a traditional gearbox and adding the Koenigsegg Direct Drive (KDD) system, Koenigsegg was able to save a comparative 88kg.
Then there’s the efficiency gains. By directing torque through gears, you begin losing potential energy as heat through friction. In comparison to a manual gearbox or CVT, the Regera prevents over 50 per cent of drivetrain efficiency losses at highway speeds, which is huge.
Hopefully that gives you an insight into the Koenigsegg Regera and the way a direct drive system can work well when combined with a hybrid drivetrain.
Would you like to see more manufacturers adopt this technology to go for huge high speeds?