Koenigsegg Regera One Gear Transmission Explained: Video
About a month ago, Topspeed published an article on the new Regera (pronounced "Re-YE-rah"); specifically, it’s transmission. Or lack thereof. Despite that, there’s still been a lot of confusion about how the Regera’s non-transmission works. To clear things up, we found this: A video from YouTuber Kyle.drive.s, aka Kyleengineers. In it, the professional race engineer and aerodynamacist explains a bit more thoroughly how the Koni Cirect Drive functions.
Just to review quickly: The engine connects to a "fluid coupling" device, which connects directly to an axle differential. On either side of the differential are a pair of 241-horsepower electric motors, which drive each wheel independently and directly. A third 214-horsepower motor drives the engine off the front of the crankshaft, allowing the 2016 Regera to accelerate on about 700 horsepower worth of electric power until the gas engine starts up. From there, the 1,100-horse gas engine pushes the car (assisted by the electric motors) to the car’s top speed.
All that’s covered pretty well by the first article. But in this video, we get an updated and slightly more in-depth look on how the whole system actually functions in real time.
Continue reading to learn more.
The Koni drive system starts with a "fluid coupling" — aka, a "torque converter."
As a lot of readers probably already know, a torque converter works a lot like a very primitive kind of continuously variable transmission. At high slip rates (when the vehicle is sitting still but the engine is revving) it multiplies torque a lot — just like a low gear. But a torque converter only multiplies torque as long as the engine is spinning faster than the transmission shaft. While it’s slipping, effectively.
For a long time, automatic transmissions got significantly worse gas mileage because even under cruise, the converter was always slipping some.
As the engine speed and transmission speed get closer, torque multiplication decreases, and the converter starts acting less like a "CVT" than it does a slipping clutch.
For a long time, automatic transmissions got significantly worse gas mileage because even under cruise, the converter was always slipping some. The solution was to install a "lock-up" clutch, which locked the engine and transmission together over 40 to 50 mph so the car could cruise efficiently. Under that speed, though, the torque converter would always slip — and thus, always multiplied torque, kind of like a CVT.
Kyle’s video starts with an explanation of the "fluid coupling" device. He confirms our educated guess from the last article; that it is basically just a typical torque converter with a lock-up function. (The note on the video says the converter locks up at 40 mph, about what we predicted in the last article).
So, essentially, the engine is really only driving the torque converter from 30 mph (when it fires up) to 40 mph, when the converter’s internal clutches lock the engine to the axle.
Kyle goes into some interesting detail here about the calculated effective gear ratios; but realistically, this system and its many interactions are so complex that there’s almost no extrapolating the real power output from pure figures.
Remember that a torque converter acts like CVT when it’s not locked up. That’s the case from 30 to 40 mph when the gas engine’s running, but it’s also true when the front (214-horse) electric motor is driving the torque converter through the engine’s crankshaft. So, below 40 mph, the front motor’s torque gets multiplied via the converter’s CVT function.
The rear motors, because they're connected directly to the wheels, don't get torque multiplication at any speed.
But here’s where things get weird. The rear motors, because they’re connected directly to the wheels, don’t get torque multiplication at any speed. That probably explains why the wheel motors are more powerful than the front motor. They need the extra power advantage at low speed, because they’re not getting the benefit of a CVT multiplication from the converter.
That also answers the question of why Koni went with a third motor on the front of the engine in the first place; not only does it serve as a super-powerful starter for the gas engine, the extra starting torque it provides through the converter means that the individual wheel motors don’t have to be ridiculously massive just to get the car moving.
Kudos to Christian K. and his engineers for that — brilliant.
Of course, that’s also got a side benefit, which Kyle mentions further on in the video. The gas engine, wonderful as it is, has the same kind of "dead spot" in the middle of its curve that a lot of engines do. Yes, that’s something they could have probably tuned out playing with variable valve timing and everything. But that’s not the Koenigsegg way.
Typical of Christian’s sledgehammer approach to problem solving, Koni dealt with that dead spot by just using the massive front motor to provide some extra shove to the engine. Acting as kind of an "electric supercharger," the front motor connected to the crankshaft fills in the dead spot, before power even gets to the torque converter. That makes for a super-smooth powerband and a linear transition without having to rely on overly complicated engine trickery.
So, all told, some stuff we’d already guessed at in terms of the converter and the lock-up function — but a bit more detail in terms of its engagement period, and a slightly deeper look at the subtle brilliance of Koenigsegg’s hybrid arrangement.
The torque multiplication factor, the kind of pseudo-CVT function, of your garden variety torque converter is one of its most unsung benefits. It’s something most people don’t even think about, since it’s just part and parcel to having a fluid coupling in the first place. But by capitalizing on that, Christian Koenigsegg has managed to make an already great system better than it needed to be. Indeed, "better" enough that it probably qualifies as one of the best hybrid systems around today.
Not bad for a guy who started out washing cars at a Suzuki dealership.
Read our full review here.