The latest BMW V8s are equipped with intake runners of continuously variable length. This system, called DIVA, is the first of its kind and is accurately described in the factory text reproduced below.
"The DIVA concept is both effective and compact in design: The four intake manifolds for each row of cylinders are shaped like a “p” or a “q”. In each case the straight section merges into the cylinder head intake duct, the circular sections forming a common drum serving as a collector. In this circular section the cross-section of the intake manifold is U-shaped and open to the inside. This opening is sealed by a flat, rotating rotor ring. Through an opening in the rotor ring, intake air is able to flow from inside the drum into the intake manifold. Turning the position of this opening, the intake manifold changes its effective length – and is shortest when the intake funnel merges directly into the intake duct. Then, with the rotor turning around its central pivot point, intake duct length is varied from 231 to 673 mm.
To provide optimum control of this sophisticated process, four rotor rings on each row of cylinders are connected to a joint axle by a fork spoke.
The two axles are adjusted by an electric motor and turn against one another. The adjustment angle depends primarily on engine speed, with the control process starting at 3500 rpm (beneath which the longest intake manifold position is maintained consistently). The total adjustment range is 236° and is covered in less than one second."