More information about the engine:
"The valvetrain is designed to expand the performance envelope of the conventional pushrod, two-valve engine while maintaining the inherent advantages in packaging efficiency and mass.
The XV16's valves are titanium alloy, an extremely lightweight material. The engine also employs titanium alloy valve springs, which are 40 percent lighter than comparable steel designs. The titanium helps increase the springs' natural frequency by 28 percent to allow for higher engine speeds.
Because of its overhead-valve architecture and roots in GM's next-generation small-block V-8, the XV16 is a perfect candidate to feature GM's Displacement on Demand (DoD) fuel-saving technology. This technology enables the engine to run seamlessly on eight or even four cylinders during typical driving conditions to maximize fuel savings.
The XV16 engine is started on all cylinders to provide fast, clean starts in all conditions. Once running, the powertrain control module activates DoD based on speed and load conditions using inputs from a number of sensors. Under light load conditions, the control module automatically closes both intake
and exhaust valves on selected cylinders. The valves are reopened to provide the number of cylinders needed for exhilarating acceleration or for hauling heavy loads.
DoD leverages the existing oil pump to provide hydraulic pressure to activate the system. The mechanical actuators are special hydraulic lifters, each with a spring-loaded locking pin that deactivates the cylinders.
These special lifters are designed so that one section can collapse, or expand, into the other section. The two sections can be either coupled or uncoupled to each other through the locking pin. When DoD is initiated, hydraulic pressure is used to dislodge the locking pin and collapse the lifter, thus closing the valve. In reactivation mode, the removal of hydraulic pressure causes the locking pin to return to its latched position, restoring the lifter's normal function.
When in V-8 or V-4 mode, a balanced combination of cylinders would be used to maintain smooth engine operation. Cylinder deactivation-reactivation operation is accomplished in a fraction of a second, making the transition seamless and transparent to the driver.
Based on GM's fuel-economy analysis, on a drive from Detroit to California, the XV16 would operate in eight-cylinder mode 65 percent of the time, four-cylinder mode 30 percent of the time, and in 16-cylinder mode only 5 percent of the time.
With the XV16's 3-step DoD system, you get the added benefit of having greater performance with all 16 cylinders in certain wide-open throttle situations such as safely passing on a two-lane road, climbing a very steep grade, or simply having fun.
As with Displacement on Demand, variable cam phasing further enhances the XV16's fuel economy, emissions and power output. An electro-hydraulically actuated position controller varies the camshaft timing relative to the crankshaft. The use of cam phasing also eliminates the need for an external exhaust gas recirculation (EGR) system to control engine-out NOx emission.
The cam phaser enables increased torque at low speeds by positioning the camshaft with an earlier inlet valve closing to trap more fresh combustion mixture. It also can be used to modify the "effective" compression ratio, allowing for increases in initial compression ratio for improved fuel economy and performance. A phaser authority of greater than 40 degrees allows for overall optimization of power, fuel economy and emissions.
This powerful engine also generates a lot of heat under high load conditions. Piston squirters allow the engine to run at higher engine speeds and loads, and keep the pistons cool. The squirters target oil at the underside of the pistons to help remove heat. Oil is also directed at the cylinder wall to help provide a quieter start-up.
The GM XV16 also uses a dry-sump scavenge pump system integrated with the main oil pressure pump. The dry-sump helps reduce overall height for improved packaging while making the vehicle capable of more aggressive cornering. The system has eight individual scavenge pumps to evacuate oil from the sump for improved performance and fuel efficiency."
(source: Cadillac press department)
In my opinion, there's nothing very advanced about this engine. Mercedes already has a shut-down feature on it's V8 and V12 engines since the introduction of the latest S Class 5 or 6 years ago. And those are not