Variable-length intake manifold

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In

Swirl

Variable geometry can create a beneficial air swirl pattern, or

double overhead camshaft (DOHC) designs, the air paths may sometimes be connected to separate intake valves^{[citation needed}

] so the shorter path can be excluded by de-activating the intake valve itself.

Pressurisation

A tuned intake path can have a light pressurising effect similar to a low-pressure supercharger due to Helmholtz resonance. However, this effect occurs only over a narrow engine speed band. A variable intake can create two or more pressurized "hot spots", increasing engine output. When the intake air speed is higher, the dynamic pressure pushing the air (and/or mixture) inside the engine is increased. The dynamic pressure is proportional to the square of the inlet air speed, so by making the passage narrower or longer the speed/dynamic pressure is increased.

Applications

Many automobile manufacturers use similar technology with different names. Another common term for this technology is variable resonance induction system (VRIS).

• Acura — Variable Volume Induction 3.0-litre V6 C30A (1991-2005) and 3.2-litre V6 C32B (1997-2005); 3.2 L V6 J32A3 (2004-2008); 2.0-litre I4 R20A (2013-2015) petrol engines
• Audi — 2.8-litre V6 petrol engine (1991–98); 3.0-litre V6 (2002-2005); 3.6 and 4.2-litre V8 engines, 1987–present
• JTS
  engines
• BMW — DISA (DIfferenzierte SaugAnlage – "Differential Air Intake"), two Port: M42, three Port: N52; DIVA (variable length runners): M54 etc. BMW's DIVA (Differentiated Variable Air Intake) used on the N62 V8 engine, is the world's first continuously variable length intake manifold.^[2]
• Citroën — XM 3,0 V6.24 (200 hp) used during 1991 to 1997, ZX Coupe 2.0 16v XU10J4 engine.
• Daewoo — Variable Geometry Induction System (VGIS) Lanos
• Dodge / Chrysler — 3.5 L V6 EGE, (1993-1997) used in Dodge Intrepid, Chrysler Concorde and LHS; 2.0 A588 - ECH (2001–2005) used in the 2001-2005 model year Dodge Neon R/T; 6.4 L V8 2011-2014 Dodge Charger and Challenger, Chrysler 300, Jeep Grand Cherokee (SRT8 versions)
• LaFerrari
• Fiat – Controlled High Turbulence (1989–92, Fiat Croma CHT), StarJet engine, dubbed Port Deactivation (PDA), Variable Intake System on the 131HP 1.8 16V and on the 155 HP 2.0 20V Pratola Serra engine.
• Yamaha V6 in the Taurus SHO. The Ford Modular V8 engines and the V6 Cologne use either the Intake Manifold Runner Control (IMRC) for four-valve engines, or the Charge Motion Control Valve (CMCV) for three-valve engines. The SVT edition (in North America) and ST170 edition (in Europe) of the Ford Focus added IMRC to the Ford Zetec engine. A system called Split Port Induction (SPI) was used on the 2.0L CVH I4 of the 1997-2002 Escort and 2000-2004 Focus, and the 3.8L Essex V6 of the 1996-2003 Windstar and 2001-2004 Mustang
  .
• LA3
  V6, LT5 5.7-litre
• E-TEC II
  engines
• Alloytec
• Accord Hybrid, Ridgeline, Honda Civic (ninth generation)
• XG
  V6
• Isuzu — Rodeo used in the second generation V6, 3.2-litre (6VD1) Rodeos, and third generation Gemini 1.6-litre 16v (4XE1) engines
• Jaguar — AJ-V6
• Sedona
• Land Rover — Variable Geometry Induction: Freelander V6 (2001-2006)
• Lancia — VIS
• inline-four engines, and Variable Resonance Induction System (VRIS) in the Mazda K engine family of V6 engines. An updated version of this technology is employed on Mazda's new Z and L engines, which is also used by Ford as the Duratec
  .
• Mercedes-Benz — V6 M112, V6 M272, V8 AMG M156
• MG — ZT 190, 180, 160 (2001-2005), ZS
  180 (2001-2005)
• 3000GT NA DOHC, 2003-2005 Eclipse
• inline-four engines, V6 engines, V8 engines
• 3.2-litre 54° V6
  engine.
• inline-four engine
  , 3.0-litre V6, 2.0 16v XU10J4 engine (non /z version)
• Boxster
• Campro IAFM - 2008 Proton Saga
  1.3
• Renault — Clio 2.0 RS
• Roewe — Variable Geometry Induction: Roewe 750 2.5 (2006–present).
• Rover 825 (1996-1999), Rover 75
  V6 (1998-2005)
• Subaru – Subaru Legacy Japan only using EJ204 (version D) 2.0 Litre, Naturally aspirated engine
• Suzuki – VIS
• 4A-GE families, and Acoustic Control Induction System
  - (ACIS) used in E, G, GR, GZ, JZ, M, S, MZ, UR, UZ, and VZ engine families.
• inline-four engine, V6 engines, VR5 engines, VR6 engines, W8 engines, V8 engines
• Volvo B52 engine as found on the Volvo 850. Longer inlet ducts used between 1,500 and 4,100 rpm at 80% load or higher.^[6]