The 999 cc in-line four of the BMW S 1000 RR received some updates, while the main characteristics are unchanged (80 mm bore, 49.7 mm stroke, “screamer” firing order). The most interesting is the presence of the ShiftCam system which varies the lift and timing of the intake valves. The camshaft, instead of the usual eight cams (one for each valve), has sixteen close in pairs. Eight have a profile designed for the best performance at low and medium revs, the other eight perform best at high speeds (higher lift and different angular position). This shaft is made up of three parts, an internal one driven by the gear moved by the chain which controls the distribution, splined, and two external ones which can slide longitudinally over the internal one. Each of the latter “serves” two cylinders and is equipped with a worm screw, above which a solenoid is positioned. Based on the RPM or torque request from the pilot, the solenoid, by pushing out a pin that engages the screw, can force a displacement of the segment in one direction or the other, causing the valves to be actuated from cams optimized for low and medium revs or from those designed for high speeds. Switching to the high-rpm cam pair takes place at 9,000rpm or from a much lower rpm (BMW did not reveal which) if the driver requests a large amount of thrust. Switching from one pair of cams to another is immediate and imperceptible: according to BMW, it takes 10 ms. Compared to a “fixed” distribution and without prejudice to all the other characteristics, this system guarantees a better volumetric efficiency along the entire delivery range, therefore more torque and more power.
The valves are in titanium. The intake ones are hollow, with a 10% weight saving compared to equivalent “full” valves. To control them, finger balancers are used, each weighing 8 grams. The maximum rotation speed is 14,600 rpm. The intake ducts are of variable height and the 48 mm diameter throttle bodies are controlled via a ride-by-wire accelerator. The gearbox is six-speed, electronic bidirectional, and the multi-disc wet clutch is anti-hopping. Water pump and oil pump are in one module. The weight of the engine is 55.8 kg.
The news of the 2023 unit they mainly concern the suction. The airbox is new and the intake ducts have a different length (the short ones are… shorter). The length change now takes place at 11,900 rpm (previously: 11,700 rpm). The head features redesigned intake ducts. They are similar to those of the M 1000 RR except that they are cast instead of machined. These updates have improved peak power from 207bhp at 13,500rpm a 210 CV a 13.750 giri/min. The peak torque value is unchanged: 113 Nm, expressed however at 11,000 rpm instead of 10,500 rpm. Other updates concern the battery (now the lithium one weighing 1.3 kg is standard) and the final drive, shortened through a chainring with an extra tooth (from 45 to 46).
