Intake Manifold: Description and Operation
DESCRIPTIONA magnesium two-stage resonance intake manifold has long runners to enhance low-speed torque and shorter runners for added horsepower. The runners, and the plenum chamber that feeds them, nest between the cylinder banks. Complex components of the multi-piece die-cast manifold are adhesive bonded together.
OPERATION
A variable intake manifold provides a marked supercharging effect to air flow entering the cylinders as the intake valve closes. Long individual tubes for each cylinder that enhance low-speed torque have a tuned length of 32.9 inches (835 mm). This length is achieved by coiling the tubes in the valley of the cylinder block. In these tubes, the air rotates 450 degrees from entry to cylinder head. To achieve a similar effect at higher speeds, a tube length of 18.3 inches (465 mm) is used. Butterfly valves in the walls of the long tubes, operated by the engine control computer, switch the flow between long and short flow paths at approximately 3700 rpm. The engine speed for switchover to the short tubes provides an imperceptible change in engine torque, because the maximum supercharging effect is consistent throughout the 2000 to 5000-rpm speed range.