Koenigsegg LST, the futuristic seven-clutch gearbox – Tech

Koenigsegg has officially presented to the world the CC850, the latest hypercar with which the Swedish company continues to pursue the dream of making the fastest cars ever conceived. Under the bonnet the car houses a powerful 5-liter V8 for 1385 horsepower, but power is not the only parameter with which to achieve record performance, as its management can also make a difference. Therefore, the technological highlight of the CC850 is its transmission, the futuristic LST already exploited on the Jesko, but further developed and equipped with a new implementation strategy, the Engage Shift System. The name LST, which stands for Light Speed ​​Transmissiontends to emphasize the exceptional shift times of the transmission made in Koenigsegg, possible thanks to the unique architecture with nine gears and seven multi-disc clutches.

To fully understand the structure and operation of the LST transmission, it is advisable to start from the operating diagram of a traditional gearbox. In the simplest case of a double ratio, common transmissions consist of an input shaft and an output shaft. The two pairs of gears to which the two gears correspond are always coupled to each other, but on the output shaft the rotation of the gear wheels is free with respect to the shaft itself. It is through the synchronizer that, during gear selection, the reference wheel is “fixed” to the shaft, rotating it integrally.
The idea behind the Light Speed ​​Transmission Koenigsegg instead is that the synchronizers are replaced by multi-disc clutches. The pairs of toothed wheels are always meshed and constantly rotate integrally with the respective shaft, ma torque and power are transmitted to the transmission output and then to the wheels by closing the clutches. In other words, the control unit opens and closes the different clutches to decide which gear to use and therefore through which pair of corresponding gears the driving power must be transmitted to the wheels.

In detail, there Light Speed ​​Transmission it consists of three trees, with three pairs of gears for the input shaft and the intermediate one and as many between the second and third shaft. Each pair of toothed wheels is controlled by a clutch, so that with 3 * 3 pairs it is possible to obtain nine possible combinations and therefore as many ratios. The count of clutches reaches six, but the last one for reverse gear management must be added to here. The LST gearbox therefore relies on multi-plate clutches for gear synchronization, reducing shift times by not having to wait for the synchronizers to intervene. This is a similar advantage to DCT dual-clutch transmissions, but the LST goes even further than that. In fact, double clutch transmissions have two concentric and two output shafts. From a purely conceptual point of view, it is as if there were two distinct gearboxes controlled by as many clutches, with one dedicated to even gears and the other to odd ones. For example, when an even gear is engaged, the second clutch disconnects the “change” of the odd gears, allowing the preselection of the next gear through the synchronizers. In this way, the next gear is already engaged when requested to change and it is sufficient to open the first clutch and close the second.

However, DCT transmissions have the limit of being able to preselect only one gear based on the forecasts of the control unit. If, for example, when using fourth gear, fifth gear was preselected but the driver wanted to shift to third, the gears should be resynchronized, lengthening the shift times. The preselection is also limited to the next or previous gear, preventing multiple jumps such as from fourth to sixth or vice versa. There Light Speed ​​Transmission Koenigsegg instead, thanks to the seven clutches, can guarantee the engagement of any gear while maintaining the advantage of the DCT gearboxes not having to wait for synchronization, cutting down on shift times. Furthermore, the LST transmission does not present particular disadvantages in terms of weight, measuring 90 kg against the 120 kg sometimes exceeded by double clutch transmissions and resulting 50% more compact in length than the gearbox installed on the Agera, the previous model to Jesko.

On Koenigsegg Jesko, the LST acted and acts like a manual gearbox supported by the UPOD strategy, Ultimate Power On Demand. At each change requested by the driver, the control unit establishes the best ratio to be selected based on the engine rotation speed and the travel speed, in order to guarantee the most adequate power and torque to satisfy the demand on the pedal. Thanks to the seven clutches, the selection through the UPOD is not limited to the immediately preceding or following relationship, but can also give rise to multiple jumps. The functions of the Light Speed ​​Transmission they are even updated on the CC850, the latest addition to Koenigsegg. In fact, the possibility of selecting a fully automatic control is introduced, with the LST which in this case behaves like a nine-speed gearbox. The driver is free, however, to return to the manual function, where the available gears drop to six, but vary according to the selected mapping. In this way, the already exceptionally short gear changes are limited, optimizing acceleration and driving continuity, making use of shorter ratios with the sportiest mappings or longer to reach high top speeds. Manual mode is controlled by the ESS system, Engage Shift Systemand also uses a clutch pedal.

There Light Speed ​​Transmission it is therefore presented as a work of high engineering. The exceptional shift times of dual-clutch transmissions are accompanied by broader selection strategies, which have an impact on faster and more effective use of engine power. With the ESS update of the CC850, the LST is also equipped with a potential manual handling, thus highlighting the sporty soul of the Koenigsegg creatures.

FP | Carlo Platella


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