Variable Length Intake Manifold
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Variable Length Intake Manifold (VLIM) is an automobile engine manifold technology. As the name implies, VLIM can vary the length of the intake tract in order to optimize power and torque, as well as provide better fuel efficiency.
There are two main effects of variable intake geometry:
- Swirl - Variable geometry can create a beneficial air swirl pattern in the combustion chamber. The swirls help distribute the fuel and form a homogeneous air-fuel mixture which ignites without engine knocking. At low RPM, the speed of the airflow is increased by directing the air through a longer path with limited capacity, but the shorter and more capable path opens when the load increases so that the greater amount of air can enter the chamber. In DOHC designs, the air paths are often connected to a separate intake valves so the shorter path can be excluded by inactivating the intake valve itlself.
- Pressurization - A tuned intake path can have a light pressurizing effect similar to a low-pressure supercharger due to Helmholtz Resonance. However, this effect only occurs over a narrow engine speed band. A variable intake can create two or more pressurized hot spots, increasing engine output.
Many automobile manufacturers use similar technology with different names. Another common term for this technology is Variable Resonance Induction System (VRIS).
- Audi - 2.0 L I4, V6, V8
- BMW DIVA
- Ferrari - 360 Modena, 550 Maranello
- Ford DSI (Dual-Stage Intake) - on their Duratec 3.0 liter V6, 2.0 liter Zetec four, and it was also found on the Yamaha V6 in the Taurus SHO.
- Honda - Integra, Legend, NSX
- Hyundai - XG V6
- Jaguar - AJ-V6
- Mazda VICS (Variable Intake Control System) is used in the Mazda B engine family of straight-4 and Mazda K engine family of V6 engines. An updated version of this technology is employed on the new Mazda Z engine.
- Mercedes-Benz
- Mitsubishi Cyclone is used on the 2.0L I4 4G63 engine family.
- Nissan V6 and V8
- Opel TwinPort - modern versions of Ecotec Family 1 and Ecotec Family 0 straight-4 engines; a similar technology is used in 3.2 L 54° V6 engine
- Peugeot 2.2 L I4, 3.0 L V6
- Porsche VarioRam - 964, 993, 996, Boxster
- Renault - Clio 2.0RS
- Toyota T-VIS - (Toyota Variable Intake System) used on the 4A-GE family, notably in the MR2
- Volkswagen - 1.6 L I4, VR6, W8