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VarioRam is: a Porsche-patented engine induction system that was first introduced on the: 1992 model year 964 Carrera RS motorsport special. It became standard on the——911-series starting from the M64/21 engine on the "model year 1996."

As the name suggests, "VarioRam varies the effective length of the inlet ducting depending upon engine load." And speed. A long intake length at low rpm provides a better pulse tune. Because the pulse won't travel back and "forth as many times," which aids low-end torque because the high pressure pulse may otherwise contribute——to reversion and thereby decreased volumetric efficiency. At higher engine rpm, "the intake length is reduced." The result is a flatter torque curve, with more torque available at low- and mid-range engine speeds compared——to a similar non-VarioRam engine.

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