Here's How the Koenigsegg Jesko's Seven-Clutch Gearbox Works

The nine-speed transmission in the Koenigsegg Jesko Is an engineering marvel.

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Oskar Bakke/Koenigsegg

The Koenigsegg Jesko is a 1600-hp, track-focused, road-legal weapon and uses a nine-speed seven-clutch gearbox Koenigsegg calls the Light Speed Transmission (LST). It’s the company’s first in-house effort, and like anything with the Koenigsegg name, it’s deeply bonkers.

This story originally appeared in the June 2019 issue of Road & Track.

Unlike a dual-clutch, the LST has no selector forks, collars, or synchronizers to engage each individual gear. Instead, selection is executed purely by opening and closing clutches. According to Christian von Koenigsegg, these clutches are capable of opening or closing in as little as two milliseconds.

Dual-clutch transmissions (DCTs) work on the same principle. One clutch opens while the other closes, allowing for wildly fast shift times. The problem is that they can only preselect a single gear at a time. The ECU guesses which ratio will be needed next, preselecting a gear. If it’s wrong, shift time suffers. For track driving, this works great, but if you’ve ever floored it on a highway with a DCT, you may have noticed it takes some time to downshift into the perfect gear.

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Cutaway rendering of the Jesko gearbox.
Wyeth Yates

Instead of two clutches, the LST uses seven—eight if you count the differential that’s part of the transaxle. These are wet, multiplate clutches with their own hydraulic actuators and pressure sensors. Each gear pair gets a clutch of its own, and the transmission uses three gear shafts instead of two, which allows for compounding gears.

The input shaft comes directly from the engine and has the option to send torque to one of three gears on the second shaft. The second shaft then has the option to send torque through one of three gears on the third shaft. Three options multiplied by an additional three options means there are a total of nine gear ratios possible. With a traditional two-shaft transmission, you need nine pairs of gears for nine gear ratios. With compound gears on three shafts, the LST only needs six gear pairs. While some automakers are stuck on addition, Koenigsegg has moved on to multiplication.

For those who have been counting clutches this whole time, one clutch per gear pair puts us at six clutches, leaving us with one remaining. The final clutch provides reverse, directly matching the input shaft to the output shaft, skipping the gear set and thus changing the direction of rotation for the output. In total, we have seven gear pairs, nine forward speeds, and one reverse. All of this adds up to 198 pounds, including fluids, in a package that’s less than half the length of the Agera’s seven-speed transmission.

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Koenigsegg founder Christian von Koenigsegg with the Regera.
Koenigsegg

Because each gear pair has a clutch, switching from one gear to another with the LST simply requires simultaneously opening and closing the respective clutches. It’s like a dual-clutch that never has to predict which gear comes next; it’s ready for whatever the driver wants. Koenigsegg calls this ultimate power on demand, or UPOD. The goal is to put you in the optimum gear for acceleration without hesitation.

UPOD works by giving the driver two shifting options. Pull the paddle shifter back one notch, and you shift one gear. Pull it all the way back, and the LST downshifts to the ideal gear for maximum acceleration. It works with upshifts as well, putting you into the highest gear possible without bogging down the engine. A console-mounted shift lever performs a similar function.

Picture yourself on the autobahn the moment you pass an unrestricted-speed-limit sign, engine humming along at a low rpm in ninth gear. Instead of sequentially dropping through each gear, with UPOD, you snap into exactly the right ratio to blast away. During full-throttle shifts, there’s never a loss of torque—one clutch disengages as the next engages. Flooring it from first gear all the way to ninth would result in uninterrupted acceleration.

Finally, a supercar that can shift to any gear as fast as it can drain a bank account.


DAILY KIT

Christian von Koenigsegg is responsible for some of the most outrageous vehicles on the planet, exercises in engineering that push the boundaries of what's possible. From carbon-fiber wheels to the new nine-gear Light Speed Transmission, the 46-year-old CEO and his company are obsessed with progress in the name of speed. We wanted to know more about his world, so we asked what he uses every day, without fail. The reliable kit.

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Wyeth Yates

TESLA MODEL 3

“It’s the best contemporary ‘normal’ daily driver around.”

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Wyeth Yates

ROLEX OYSTER PERPETUAL

“A no-frills, self-winding automatic with date display, and it will work after a big solar flare knocks out all electric equipment.”

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Wyeth Yates

FUJISTU LAPTOP

"To make everything happen anywhere: design, engineering, finance, marketing, you name it.”

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Wyeth Yates

BRAUN ELECTRIC TOOTHBRUSH

“Such a difference in mouth freshness compared with a manual toothbrush.”

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