Koenigsegg Regera’s Non-Transmission
"Something’s happening here, and what it is ain’t exactly clear."
So then, what about this new driveline that Christian K. has come up with? Let’s take a look.
First, don’t call the Koenigsegg Regera’s drive system a “gearless transmission.” Not because there’s no such thing as a “gearless transmission,” but simply because the Koenigsegg Direct Drive isn’t a transmission. A transmission, by definition, varies input speed to output speed. As you might have gathered from the name, the Koni “Direct Drive” doesn’t do that.
The Regera has a truly psychotic power-to-weight ratio. With 1,100 horsepower drawn from its 5.0-liter, twin-turbo V-8 engine and 3,600 pounds to move, few vehicles on Earth can lay claim to comparable power-to-pound ratios. But faster is better, and doing it with less fuel is better still, so read on to unravel this new technology.
Continue reading to learn more about the Koenigsegg Regera.
At its heart, the KDD is what you might call “electrically augmented direct drive.” Direct drive, as in the engine connects directly to the wheels via a fixed gearset, and engine rpm is directly fixed to vehicle speed.
Normally, that doesn’t work – internal combustion engines make so little torque off of idle that they usually need a steeper gear reduction to get the car moving. However, that isn’t necessarily the case when you’re talking about vehicles with an absurd power-to-weight ratio and massive low-rpm torque. My fellow nitro-friends in Top Fuel have been using direct drive for quite some time now; turns out a 10,000-horsepower engine is plenty capable of getting a 2,500-pound car off the line without gear reduction.
Koni also relies on its massively powerful engine to deliver torque just off idle, in this case through what it describes as a “fluid coupling.” Koni hasn’t said whether said fluid coupling is a torque converter, but it’s probably safe to assume it is. It makes mention of the drive “coupling and decoupling” after engagement, though that could just as easily refer to a beefed-up lockup mechanism as anything else.
Power goes from there through a differential, likely some type of limited slip. After leaving the differential, power heads to the wheels via axle shafts, and the axle’s deep 2.85-to-1 gear ratio carries the Regera up to a claimed 248 mph.
Tech-savvy readers will likely note that this arrangement isn’t exactly conducive to acceleration off the line. While the 5.0-liter makes horrendous power over 2,500 rpm, this system alone would probably result in the same kind of 0 to 60 times as a Dodge Viper launched in third gear. The Regera needs something to add some low-speed torque, and electric motors are just the thing for it.
The Regera’s drive system uses three electric motors to provide extra torque for acceleration at low rpm.
A 214-horsepower electric motor bolts to the front of the mid-mounted engine’ s crankshaft. Ahead of this motor (low and along the centerline of the car) sits the lithium-ion battery pack, which holds enough power to provide 31 miles of electric-only range on a full charge.
On either side of the differential, where the axle shafts bolt to it, are two more, disc-shaped electric motors. These innovative “axial flux” motors are extremely power-dense for their size, adding an extra 241 horsepower each to the proceedings. With the electrics and gas engine working together, the Regera puts out a crushing 1,500 horsepower with a torque curve so flat it seems practically fictional.
“Wait,” you’re saying. “Something’s not right here.
1,100 + 214 + 241 + 241 = 1,796 horsepower.
Aren’t we missing 300 horses here?"
Yes, astute reader, and no.
Remember that internal combustion engines and electric motors make power differently. Electric motors generally make maximum torque at very low rpm; it drops off almost linearly as rpm increases. There’s no guarantee that an electric motor is going to hit peak horsepower in the same rpm range as the gas engine – and in fact, in this particular application, that wouldn’t be the ideal anyway. The electric motors’ primary jobs are to provide starting torque and powerful brake regen, so it’s reasonable to expect they’d peak at a lower rpm than the gas engine.
So, it’s not that your 300 horsepower is GONE – it’s that the powertrain is making 300 MORE throughout the rpm range, especially below the gas engine’s horsepower peak. That’s a very good thing when you’re talking about driveability, and linear and immediate throttle response. The brilliance of this drivetrain is that it uses both power sources – gas and electric – where they’re used best. Electric for massive starting torque, and gas for huge top-end horsepower.
There’s a lot to be gained by getting rid of a transmission. First, even the best of them suck up 15 to 20 percent of the engine’s power, which translates to lost acceleration, top end, fuel economy while cruising and the amount of energy recaptured by the regen system.
However, transmissions are usually required when running a parallel hybrid system, which converts less energy and is inherently more efficient than a pure series hybrid. Most of the time, we pay an 8 to 10 percent toll to entropy when converting mechanical energy to electric, and another 8 to 10 percent when converting it back again. The less energy you have to convert, the less you send out into the universe as waste. This was the primary reason Christian Koenigsegg opted for a parallel system over a series.
Structurally, there’s a kind of simple brilliance in the architecture. With the engine connected to a generator on one side, and the wheels running individual electric motors on the other, there’s all the room in the world for versatility in programming the brake regen or running cycles for maximum power or efficiency.
Another perk of running individual wheel motors is, of course, torque vectoring. That is, varying the amount of power sent from side-to-side while cornering. With this system, you could brake the inside wheel and power the outside wheel during a turn, which keeps the car safely and reliably on the racing line. Torque vectoring alone has proven reason enough for the hyper-est of the hypercars to go hybrid; in this respect at least, Koni is following in the footsteps of Porsche’s 918, and McLaren’s P1 Widowmaker.
Finally, getting rid of the transmission reduces weight and complexity, which is a central preoccupation of any Swedish engineer worth his salted fish.
I wouldn’t say that it would be impossible to adapt this system to a non-hypercar – technology happens. Things that are impractical today may become practical in the future, assuming the technology catches up. So, don’t write the Koenigsegg Direct Drive system off as hypercar exotica just yet.
But don’t bet on it showing up in the 2021 Honda Civic.
That said, there’s no reason the KDD couldn’t show up in some form in future ridiculous hypercars from other manufacturers. In that very specific application, it’s a real contender. It would probably be augmented by additional front-wheel motors for all-wheel drive and four-wheel brake regen – which is a serious weakness for any rear-drive electric car. Regardless, the brilliant simplicity of the KDD system is bound to find adherents among other hypercar manufacturers, and it’s only a matter of time before they start running out of excuses NOT to use it.