VarioRam is a

Porsche Dr. Ing. h.c. F. Porsche AG, usually shortened to Porsche (; see below), is a German automobile manufacturer specializing in luxury, high-performance sports cars, SUVs and sedans, headquartered in Stuttgart, Baden-Württemberg, Germany. Th ...

-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 In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

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.

References

Porsche Engine technology {{Automotive-tech-stub