Editing Variable-length intake manifold

{{Short description|Internal combustion engine technology}}
{{Refimprove|date=June 2009}}
[[Image:Lower-intake-manifold.jpg|thumb|Lower intake manifold on a 1999 Mazda Miata [[Mazda B engine#BP-4W|engine]], showing components of a variable-length intake system.]]

In [[internal combustion engine]]s, a '''variable-length intake manifold''' ('''VLIM'''),'''variable intake manifold''' ('''VIM'''), or '''variable intake system''' ('''VIS''') is an [[automobile]] internal combustion engine [[Inlet manifold|manifold]] technology.  As the name implies, VLIM/VIM/VIS can vary the length of the intake tract in order to optimise [[power (physics)|power]] and [[torque]] across the range of engine speed operation, as well as to help provide better [[fuel efficiency]]. This effect is often achieved by having two separate intake ports, each controlled by a valve, that open two different manifolds – one with a short path that operates at full engine load, and another with a significantly longer path that operates at lower load. The first patent issued for a variable length intake manifold was published in 1958, US Patent US2835235 by [[Daimler Benz AG]].<ref>[https://patents.google.com/patent/US2835235 US Patent 2835235]</ref>

There are two main effects of variable intake geometry:
;Swirl: Variable geometry can create a beneficial air swirl pattern, or [[turbulence]] in the [[combustion chamber]].  The swirling helps distribute the fuel and form a [[wiktionary:homogeneous|homogeneous]] air-fuel mixture. This aids the initiation of the [[combustion]] process, helps minimise [[engine knocking]], and helps facilitate complete combustion.  At low [[revolutions per minute]] (rpm), the speed of the airflow is increased by directing the air through a longer path with limited capacity (i.e., cross-sectional area) and this assists in improving low engine speed torque.  At high rpm, the shorter and larger path opens when the load increases, so that a greater amount of air with least resistance can enter the chamber. This helps maximise 'top-end' power.  In [[overhead camshaft#Double overhead camshaft|double overhead camshaft]] (DOHC) designs, the air paths may sometimes be connected to separate [[poppet valve|intake valve]]s{{citation needed|date=November 2009}} so the shorter path can be excluded by de-activating the intake valve itself.
;Pressurisation: A [[engine tuning|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 [[automotive industry|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&nbsp;L V6 J32A3 (2004-2008); 2.0-litre I4 R20A (2013-2015) [[petrol engine]]s
*[[Audi]] — 2.8-litre V6 [[petrol engine]] (1991–98); 3.0-litre V6 (2002-2005); 3.6 and 4.2-litre [[V8 engine]]s, 1987–present
*[[Alfa Romeo]] — [[Alfa Romeo Twin Spark engine#Modular Inlet Manifold|Twin Spark 16v]] (1.8 and 2.0-litre) and [[JTS engine|JTS]] engines
*[[BMW]] — '''DISA''' (DIfferenzierte SaugAnlage – "Differential Air Intake"), two stage: [[BMW M42|M42]], [[BMW M44|M44]], [[BMW M54|M54]], [[BMW N62|N62TU]], three stage: [[BMW N52|N52]]; '''DIVA''' (continuously variable length runners): [[BMW N62|N62]], is the world's first continuously variable length intake manifold.<ref>{{cite journal |last1=Hirschfelder |first1=Klaus |last2=Völkl |first2=Werner |last3=Kühnel |first3=Hans-Ulrich |last4=Sinn |first4=Walther |last5=Huck |first5=Armin |title=The first continuously variable intake system in the new eight-cylinder engine from BMW |journal=MTZ Worldwide |date=March 2002 |volume=63 |issue=3 |pages=2–6 |doi=10.1007/bf03227525 |language=en |issn=2192-9114}}</ref>
*[[Citroën]] — XM 3,0 V6.24 (200&nbsp;hp) used during 1991 to 1997, ZX Coupe 2.0 16v XU10J4 engine.  
*[[Daewoo Motors|Daewoo]] — '''Variable Geometry Induction System''' ('''VGIS''') [[Daewoo Lanos|Lanos]]  
*[[Dodge]] / [[Chrysler]] — 3.5&nbsp;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&nbsp;L V8 2011-2014 Dodge Charger and Challenger, Chrysler 300, Jeep Grand Cherokee (SRT8 versions)
*[[Ferrari]] — [[Ferrari 360 Modena|360 Modena]], [[Ferrari 550 Maranello|550 Maranello]], [[Ferrari LaFerrari|LaFerrari]]
*[[Fiat]] – '''Controlled High Turbulence''' (1989–92, [[Fiat Croma|Fiat Croma CHT]]), [[Fully Integrated Robotised Engine|StarJet engine]], dubbed '''Port Deactivation''' (PDA), '''Variable Intake System''' on the 131HP 1.8 16V and on the 155 HP 2.0 20V [[Fiat Pratola Serra modular engines|Pratola Serra engine]].
*[[Ford Motor Company|Ford]] — '''Dual-Stage Intake''' ('''DSI'''), on their [[Duratec]] 2.5 and 3.0-litre V6s, and it was also found on the [[Yamaha Motor Corporation|Yamaha]] V6 in the [[Ford Taurus|Taurus SHO]]. The [[Ford Modular engine|Ford Modular V8 engines and the V6 Cologne]] use either the '''Intake Manifold Runner Control''' ('''IMRC''') for [[multi-valve|four-valve]] engines, or the '''Charge Motion Control Valve''' ('''CMCV''') for three-valve engines. The [[Special Vehicle Team|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 [[Ford CVH engine#2.0|2.0L]] CVH I4 of the 1997-2002 [[Ford Escort (North America)|Escort]] and 2000-2004 [[Ford Focus|Focus]], and the [[Ford Essex V6 engine (Canadian)#3.8|3.8L Essex V6]] of the 1996-2003 [[Ford Windstar|Windstar]] and 2001-2004 [[Ford Mustang|Mustang]].
*[[General Motors]] — 3.9-litre [[GM High Value Engine|LZ8/LZ9]] V6, 3.2-litre [[GM 54-Degree V6 engine|LA3]] V6, LT5 5.7-litre
*[[GM Korea]] — [[overhead camshaft#Double overhead camshaft|DOHC]] versions of  [[E-TEC II]] engines
*[[Holden]] — [[Alloytec]]
*[[Honda]] — [[Honda Integra|Integra]], [[Honda Legend|Legend]], [[Honda NSX|NSX]], [[Honda Prelude|Prelude]], [[Honda R engine|Civic]], [[Honda Accord Hybrid|Accord Hybrid]], [[Honda Ridgeline|Ridgeline]], [[Honda Civic (ninth generation)]]
*[[Hyundai Motor Company|Hyundai]] — [[Hyundai XG|XG]] V6
*[[Isuzu]] — [[Isuzu Rodeo|Rodeo]] used in the second generation V6, 3.2-litre (6VD1) Rodeos, and third generation Gemini 1.6-litre 16v (4XE1) engines
*[[Jaguar (car)|Jaguar]] — [[Jaguar AJ-V6 engine|AJ-V6]]
*[[Kia]]  — [[Carnival]], [[Sedona]]
*[[Land Rover]] — '''Variable Geometry Induction''': [[Land Rover Freelander|Freelander]] V6 (2001-2006)
*[[Lancia]] — '''VIS'''
*[[Mazda]] — '''Variable Inertia Charging System''' ('''VICS''') is used on the [[Mazda FE-DOHC engine]] and [[Mazda B engine]] family of [[inline-four engine]]s, and '''Variable Resonance Induction System''' ('''VRIS''') in the [[Mazda K engine]] family of [[V6 engine]]s.  An updated version of this technology is employed on Mazda's new [[Mazda Z engine|Z]] and [[Mazda L engine|L]] engines, which is also used by [[Ford Motor Company|Ford]] as the [[Ford Duratec engine|Duratec]].
*[[Mercedes-Benz]] — V6 [[Mercedes-Benz M112 engine|M112]], V6 M272, V8 AMG M156
*[[MG Cars|MG]] — [[MG ZT|ZT]] 190, 180, 160 (2001-2005), [[MG ZS (2001)|ZS]] 180 (2001-2005)
*[[Mitsubishi]] — '''Mitsubishi Variable Induction Management (MVIM)''' 1991-1999 [[Mitsubishi GTO|3000GT]] NA DOHC, 2003-2005 [[Mitsubishi Eclipse|Eclipse]]
*[[Nissan]] — [[inline-four engine]]s, [[V6 engine]]s, [[V8 engine]]s
*[[Opel]] — '''DUAL RAM''' – select six-cylinder [[Opel cam-in-head engine]]s; '''TWINPORT''' – modern versions of [[Ecotec Family 1]] and [[Ecotec Family 0]] [[inline-four engine]]s and [[straight-three engine|inline-three engine]]s; a similar technology is used in [[GM 54-Degree V6 engine|3.2-litre 54° V6]] engine.
*[[Peugeot]] — 2.2-litre [[inline-four engine]], 3.0-litre V6, 2.0 16v XU10J4 engine (non /z version) 
*[[Porsche]] — [[Porsche 928|928]] "flappy",<ref>{{cite web|title=928 Tech Tips: Tip 78|url=http://jenniskens.livedsl.nl/Technical/Tips/0/MyTip078.htm}}</ref><ref>{{cite web|title='90 GT Flapectomy|url=http://www.tower-mt.com/pics/davids_gt/Flapectomy-1/pres0036.html}}</ref> '''[[VarioRam]]''', [[Porsche 964|964]], [[Porsche 993|993]], [[Porsche 996|996]], [[Porsche Boxster|Boxster]]
*[[Proton (carmaker)|Proton]] — '''[[Campro engine#Campro CPS and VIM engine|Campro CPS and VIM]]''', [[Proton Gen-2|Proton Gen-2 CPS]] and [[Proton Waja|Proton Waja CPS]]; Proton '''[[Campro engine#Campro IAFM engine|Campro IAFM]]''' - 2008 [[Proton Saga]] 1.3
*[[Renault]] — [[Renault Clio|Clio 2.0 RS]]
*[[Roewe]] — '''Variable Geometry Induction''': [[Roewe 750]] 2.5 (2006–present).
*[[Rover Group|Rover]] — '''Variable Geometry Induction''': [[Rover 800 Series|Rover 825]] (1996-1999), [[Rover 75]] V6 (1998-2005)
*[[Subaru]] – [[Subaru Legacy (fourth generation)|Subaru Legacy]] Japan only using EJ204 (version D) 2.0 Litre, Naturally aspirated engine
*[[Suzuki]] – VIS
*[[Toyota]] — '''Toyota Variable Induction System''' ('''[[T-VIS]]'''), used in the early versions of the [[Toyota G engine#1G-GEU|1G-GEU]], [[Toyota S engine#3S-GTE|3S-GTE]], [[Toyota S engine#3S-GE|3S-GE]], and [[Toyota 4A-GE|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.
*[[Volkswagen]] — 1.6-litre [[inline-four engine]], [[V6 engine]]s, [[VR5 engine]]s, [[VR6 engine]]s, [[W8 engine]]s, [[V8 engine]]s
*[[Volvo]] — '''V-VIS'''<ref>{{cite web |language=en |url=http://www.paerl.it/volvo/vvismanualeng.pdf |title=Modified VVIS control |website=www.paerl.it |date=2011-12-11 |archive-url=https://web.archive.org/web/20170711174355/http://www.paerl.it/volvo/vvismanualeng.pdf |archive-date=2017-07-11 |access-date=2017-12-21 |url-status=live}}</ref> ('''Volvo Variable Induction System''') [[Volvo B52 engine]] as found on the [[Volvo 850]]. Longer inlet ducts used between 1,500 and 4,100&nbsp;rpm at 80% load or higher.<ref>{{cite web |language=en |url=http://www.volvoclub.org.uk/tech/850GLT-EngineTechInfo.pdf |title=EngineTechInfo |author=Volvo Car Corporation |access-date=2017-12-21 |url-status=live|archive-url=https://web.archive.org/web/20160817174510/https://www.volvoclub.org.uk/tech/850GLT-EngineTechInfo.pdf|archive-date=Aug 17, 2016}}</ref>

== References ==
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{{Automotive engine |collapsed}}

{{DEFAULTSORT:Variable-Length Intake Manifold}}
[[Category:Engine technology]]