The two-stage bit means there are two turbochargers plumbed in sequence, so that they both feed pressurized intake air to all eight cylinders. Don’t call it a twin-turbo setup, though, because as with all sequential arrangements, these turbochargers are significantly different in size. (Twin turbos are the same size, with each one feeding half the engine’s cylinders.) The smaller of the two turbos provides boost at low engines speeds, where the lighter compressor and turbine spin up to speed quicker to reduce lag. However, at higher revs and engine load, when the engine is pumping more air, the smaller turbine and compressor begin to reach their limits. Instead of increasing power, they become restrictions in both the intake and exhaust streams, choking the intake supply and increasing back pressure in the exhaust. This is when the larger turbocharger takes over, raising the overall boost pressure and peak power output.
