Forget sequential. Forget automated manual. Forget dual clutch. And, thank goodness, forget the CVT. There’s a new champion on the block when it comes to the fastest gearshift in town, and it goes by the name Lightspeed. It’s the new multi-clutch transmission in the Koenigsegg Jesko and it might shift your whole world view.
An automated manual, like BMW’s SMG, can shift up or down just one gear at a time if it wants to go quickly. The same for a dual-clutch box like VW’s DSG or the Porsche PDK. If you want to jump an odd number of gears, that lightning-fast reflex slows down. Ask for a downshift when it was expecting an upshift, and even single-gear changes slow down. That wouldn’t do for a car from Koenigsegg. So they came up with something better. A gearbox with not just one or two, but with seven clutches. Plus an extra clutch on the differential!
Koenigsegg uses a dual-clutch box in its existing cars. Like the Agera. But the company says that once you got above 1,100 lb-ft of torque, a conventional box couldn’t deal with the twist. And if it could, it would have made it extremely heavy. That’s why the Regera dropped the gearbox completely and just used the gas engine to power three electric motors. The motors powered the wheels instead of the engine.
For the LST, Koenigsegg wanted something better. And something better didn’t exist, so it built its own.
A dual-clutch transmission uses two transmission shafts. One holds the even-numbered gears, the other the odd. That’s why it can only execute the quickest shifts when it’s one up or one down. The second shaft, with the next gear, is all ready to go. Lined up by the computer. Ask for two down, for example, and it’s on the same shaft as the already engaged gear.
Koenigsegg uses three shafts for its nine speeds. And each shaft gets two clutches. So even if you’re asking for a gear on the same shaft, it can just use the other clutch to engage the gear you want.
The automaker isn’t spelling out how exactly the entire mechanism works. They do need to keep some secrets, after all, but it seems to be just that simple. Take the idea of a DSG and add more mechanisms. Since there’s always an available clutch you can pick any gear nearly instantaneously. Hydraulic actuators snap the clutch into engagement and you’re off.
The extra shafts and plethora of clutches make Lightspeed shifts possible. Since six of the nine speeds you could pick from are on different shafts, and since every clutch has its own actuator, sequential blasts through gears are quick and easy. The next gear up or down is always ready to go.
But, you’re probably thinking, didn’t you say that this wasn’t limited to the one at a time shift of a DCT? You’re right. But conventional shift paddles are. So Koenigsegg has added what it calls dual-mode shifting.
Use the paddles, or the center-mounted shifter, conventionally and you get single-gear changes. Pop the paddles and you get one gear for each pop. As you would expect. They’re just really quick.
The paddles, and that shifter, though, have a second notch. Pull harder and you hit the second notch. That engages Koenigsegg’s UPOD gear change system.
UPOD uses the car’s sensors. Like vehicle speed and RPM. It calculates which gear would give you maximum power at any moment and which gear would give you maximum economy.
Push the paddle or shift stick to the second notch and UPOD doesn’t call up the next gear, it calls up the “optimal gear for maximum acceleration”. Yes please! Because of the multiple clutches and shafts, the car can go instantly from, say, seventh to fourth–or even first gear–with no intermediate stops along the way, like you’d have in a dual-clutch box. The same thing you can do with a conventional manual, but it can do it far faster than you could ever push your leg and move the stick.
It can work the other way too, though there’s probably not as much demand for that. If you’re in second and you’re done accelerating, which seems likely in a car with a billion horsepower, engage the second notch up and it will jump immediately to ninth. Or whichever gear will maximise fuel economy.
Yes, it’s possible that you could be in a gear and want the gear that shares a clutch with it. But the one you’re using would also have to be using the shared clutch instead of the other one and the company has probably arranged the cogs to make that an uncommon situation. So it’s a possibility, but a rare one.
There are, though, several ways that Koenigsegg could work around that. Enough that it might be able to completely avoid the possibility. And since the company isn’t offering up exactly how the internal bits function, they’ve probably figured it out.
A transmission with that many gears may sound like a monster, but Koenigsegg says it’s actually pretty small. The company says optimisation of the system means that not only is it tiny–it’s only half as long as the seven-speed they used to use–but it weighs just 90 kg, too. That puts it at about half the weight of the likes of McLaren or Ferrari transmissions.
So it’s lighter, smaller, and faster-shifting than other gearbox options. Which makes sense for a hypercar as extreme as the Jesko.
The post How it Works: The Koenigsegg Jesko’s Lightspeed, Seven Clutch Transmission appeared first on Swedespeed.
