In internal combustion engines, a variable length intake manifold (VLIM), or variable intake manifold (VIM) is an automobile internal combustion engine manifold technology. As the name implies, VLIM/VIM can vary the length of the intake tract - in order to optimise power and torque across the range of engine speed operation, as well as help provide better fuel efficiency.
There are two main effects of variable intake geometry:
Many automobile manufacturers use similar technology with different names. Another common term for this technology is variable resonance induction system (VRIS).
Ford - The 2.0L Split Port engine features an Intake Manifold Runner Control variable geometry intake manifold.