The Koenigsegg Jesko debuted this year as the new king of Swedish supercars, and its tantalizing performance specs are possible due to remarkable engineering.
One of the many marvels of ingenuity is what Koenigsegg calls the "Light Speed Transmission," its 9-speed transmission that doesn't need to shift through gears like a traditional dual-clutch automatic. To help explain the witchcraft going on inside of the transmission, Jason Fenske of "Engineering Explained" is here—whiteboard and all.
The short and sweet is this: The LST doesn't include synchros and does not need to shift through multiple gears to select the optimal one. For example, if the driver wants fourth gear for maximum acceleration in the moment, the transmission does not shift through fifth or sixth gears. It swaps almost immediately to fourth.
So, what's going on inside? The twin-turbo 5.0-liter V-8 is hooked up directly to the input shaft. There isn't a flywheel. There are seven gears that are on bearings, while the others rotate together in a fixed fashion across three shafts. Each shaft has separate gear pairs, which leads to compound gears. This is different from a traditional DCT.
When the engine sends power to the input shaft, the input shaft then has the choice of three gears on the second shaft (there are another three gears on the second shaft that are fixed) and each of those three gears has its own clutch pack connected. Closing clutch pack one forces the input shaft to rotate the second shaft, and from there, power flows to the third shift with three individual gears on bearings. The car can choose which one to send power to. Ultimately, two clutch packs need to close to send power to the rear wheels. We promise it's much easier to comprehend with the whiteboard drawings as visual help.
Now that we know what's going on, how does the Jesko shift from, say, ninth gear to second gear without flipping through every other speed? Ninth gear means clutch packs three and six are closed and everything else is open. Second gear requires clutch packs one and five to close. Immediately, the car opens three and six, and one and five close nearly simultaneously.
The engineering is, frankly, marvelous. Check out more comparisons to a standard DCT and more from Jason in the video above.