The new KTM Super Duke R would have arguably made headlines for its larger displacement, but the generation of intelligent valve timing hidden inside the cylinder heads, which is also worth talking about.
Variable valve timing is nothing new: Honda’s Hyper-VTEC design has been around for decades, and more recently, Suzuki has used a clever mechanical setup to circumvent the MotoGP regulations that its GSX-R1000 engines have discovered. Even the 125-level machines in Yamaha’s diversity use this technology.
But it’s rarer to see motorcycles that replace the timing and lift of the cams, which KTM’s cam shift formula allows, with the goal of achieving a wider distribution of force and torque across the entire rev range. . Not that the old 1290 diversity ever did. disappeared in this area. . .
“Duration” is the length of time the valve stays open and “elevation” is the distance it opens. The high lift and duration allow you to get more air and fuel into the cylinder, but the smaller, shorter valve openings have an effect on the low. final torque, emissions and throttle response.
KTM’s design concept is based on the BMW ShiftCam formula and, like variable maximum valve formulas for motorcycles, is fostered through cars. This specific concept can be traced back to the Audi Valvelift formula that debuted in 2008.
It features an intake camshaft made up of a splined central shaft with the lobes mounted on a sliding sleeve that slots over it. There are two cam lobes for each valve – a ‘mild’ lobe with less lift and duration, and a ‘wild’ one with lots of lift and duration.
The trick is to perform the transfer between the two lobes of the cam incredibly temporarily and at just the right time to prevent the fast-moving engine parts from colliding (thing).
The engine will need to perform the replacement while the intake valves are closed so that there is no tension between the lobes and hands between them and the valve stems. To do this reliably, KTM’s formula, like Audi’s AVS and BMW’s ShiftCam, uses two solenoids. actuators and a pair of machined spiral channels on the camshaft sleeve.
Activate a solenoid and insert a pin into the first coiled channel, pulling the sleeve that carries the cam lobes in one direction and engaging the cam lobe.
Put 12V to the second solenoid and it inserts a pin into the other spiral groove, moving the sleeve the other way to engage the racier cam profile. Because the spirals are cut into the same sleeve that carries the cam lobes, the movement is always timed to happen when the valves are closed, and the grooves are shaped to push the pins back out again when their work is done, within one rotation of the camshaft, so there’s no chance of both solenoids trying to engage simultaneously.
The solenoids themselves are fitted in a single unit called a ‘double pin actuator’, and KTM’s are actually from external supplier ETO Gruppe, with a switching time of less than 22 milliseconds. The whole lot is controlled by the engine ECU, using revs and throttle position to decide when to switch between the lobes.
The main difference between KTM’s system and the ShiftCam used on BMW’s boxer twins is the position of the actuator and spiral grooves.
BMW has an extension at the end of the camshaft for the mechanism, which adds the length of the cylinder head but lets the actuator lie flat over the cam cover.
It would be exposed to potential damage and would further widen the already wide engine if it were above the cam cover. With a V-twin than with a boxer, KTM’s precedence is different, so the spiral channels sit between the two sets of intake cams. The lobes and actuators are fixed on the most sensitive part of the cam covers, keeping the rest of the head as compact as those without a variable valve timing system.