Dual Runner Manifold
A dual runner manifold like on the F22/B18C1/H22A has two passages for air to flow. When in a low rpm range the long runners are engaged to promote torque production.
Adapted from pgmfi.org wiki
A dual runner manifold like on the F22/B18C1/H22A has two passages for air to flow. When in a low rpm range the long runners are engaged to promote torque production. When the engine reaches a higher rpm the butterflys open and let the air go through the short runners which helps with high rpm power.
Credits and source
Source Adapted from Dual Runner Manifold on pgmfi.org wiki. Licensed under CC BY-NC-SA 1.0.