Editing VTEC (section)

== i-VTEC ==
Honda i-VTEC (intelligent-VTEC)<ref>{{cite web |url=http://www.acura.com/index.aspx?initPath=TSX_Learn_FeaturesOptions_Performance_Engine_iVTEC |title=acura.com |publisher=acura.com |access-date=2010-12-04 |archive-date=2008-06-24 |archive-url=https://web.archive.org/web/20080624071723/http://www.acura.com/index.aspx?initPath=TSX_Learn_FeaturesOptions_Performance_Engine_iVTEC |url-status=live }}</ref> is a system that combines VTEC with Honda's VTC (Variable Timing Control), a continuously variable camshaft phasing system used on the intake camshaft of DOHC VTEC engines. The technology first appeared on Honda's [[Honda K engine|K-series]] four-cylinder engine family in 2001. Most Honda or Acura four-cylinder powered vehicles sold in the United States used i-VTEC by the 2002 model year with the exception being the 2002 Honda Accord.

VTEC controls of valve lift and valve duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees, depending upon engine configuration. Phasing is implemented by a computer-controlled, oil-driven adjustable cam sprocket. Both engine load and RPM affect VTEC. The intake phase varies from fully retarded at idle to somewhat advanced at full throttle and low RPM. The effect is further optimization of torque output, especially at low and midrange RPM. There are two types of i-VTEC K series engines which are explained in the next section.

Honda's J-Series SOHC engines use an entirely different system also, confusingly, marketed as i-VTEC. Honda J-Series Engines using i-VTEC combine SOHC VTEC operation with Honda [[Variable Cylinder Management|VCM (Variable Cylinder Management)]] variable displacement technology to improve fuel economy under light loads.

=== K-Series ===
{{main|Honda K engine}}
{{Unreferenced section|date=July 2013}}

The K-Series engines have two different types of i-VTEC system implementations. The first type is for performance engines like the K20A2 or K20Z3 used in the 2002-2006 [[Acura RSX|RSX]] Type S or the 2006-2011 [[Honda Civic Si|Civic Si]] and the second type is for economy engines like the K20A3 or K24A4 used in the 2002-2005 [[Honda Civic Si|Civic Si]] or 2003-2007 [[Honda Accord|Accord]]. The performance i-VTEC system is basically the same as the DOHC VTEC system of the [[Honda B engine#B16A4|B16A's]]. Both intake and exhaust cams have three cam lobes per cylinder. However, the valvetrain has the added benefit of roller rockers and VTC continuously variable intake cam timing. Performance i-VTEC is a combination of conventional DOHC VTEC with VTC (which operates for intake valves only). The VTC is available in the economy and performance i-VTEC engines.

The economy i-VTEC used in K20A3/K24A4 engines is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. At low RPM only one valve on the intake opens fully, promoting combustion chamber swirl and improved fuel atomization. This allows a leaner air/fuel mixture to be used, improving fuel economy. At higher RPM, both intake valves run off the larger intake cam lobe, improving total air flow and top-end power.

The two types of engines are easily distinguishable by the factory rated power output: the performance engines make around {{convert|200|hp|abbr=on}} or more in stock form, while the economy engines do not make much more than {{convert|160|hp|abbr=on}}.

=== R-Series ===
{{main|Honda R engine}}

The i-VTEC system in the
R-Series engine uses a modified SOHC VTEC system consisting of one small and two large lobes. The large lobes operate the intake valves directly while the small lobe is engaged during VTEC. Unlike typical VTEC systems, the system in the R-Series engine operates in a 'reverse' fashion engaging only at low to mid RPMs. At low RPMs, the small lobe locks onto one of the larger lobes and keeps one of the intake valves partially open during the compression cycle, similar to the [[Atkinson cycle]]. The ability for Honda to switch between Atkinson cycle and normal cycle allows excellent fuel efficiency without sacrificing too much performance.

=== i-VTEC with Variable Cylinder Management (VCM) ===
In 2003, Honda introduced an i-VTEC V6 (an update of the [[Honda J engine|J-series]]) that includes Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below {{convert|80|km/h|mph|abbr=on}}) operation. According to Honda,
<blockquote>
VCM technology works on the principle that a vehicle only requires a fraction of its power output at cruising speeds. The system electronically deactivates cylinders to reduce fuel consumption. The engine is able to run on 3, 4, or all 6 cylinders based on the power requirement, essentially getting the best of both worlds. V6 power when accelerating or climbing, as well as the efficiency of a smaller engine when cruising.{{quote without source|date=April 2023}}
</blockquote>
The technology was originally introduced to the US on the 2005 [[Honda Odyssey (North America)|Honda Odyssey]] minivan, and can now be found on the Honda Accord Hybrid, the 2006 Honda Pilot, and the 2008 Honda Accord. Example: EPA estimates for the 2011 (271&nbsp;hp SOHC 3.5L) V6 Accord are 24 mpg combined vs. 27 in the two 4-cylinder-equipped models.

i-VTEC VCM was also used in the [[Honda L engine#LDA-MF5 (3stage i-VTEC + IMA)|1.3-liter LDA engine]] used in the 2001-2005 [[Honda Civic Hybrid]].<ref>{{cite web |url=http://autospeed.com/cms/title_Honda-Civic-Hybrid-Technology/A_3067/article.html |title=Honda Civic Hybrid Technology |publisher=Autospeed.com |access-date=2010-12-04 |archive-date=2011-07-28 |archive-url=https://web.archive.org/web/20110728125450/http://autospeed.com/cms/title_Honda-Civic-Hybrid-Technology/A_3067/article.html |url-status=live }}</ref>

=== i-VTEC i ===
A version of i-VTEC with [[gasoline direct injection|direct injection]], first used in 2004 [[Honda Stream]].<ref>{{cite web |url=http://world.honda.com/HDTV/news/2003-4031127a/ |title=Honda Worldwide |publisher=World.honda.com |access-date=2012-11-07 |url-status=dead |archive-url=https://web.archive.org/web/20140515052532/http://world.honda.com/HDTV/news/2003-4031127a/ |archive-date=2014-05-15 }}</ref>
Direct injection 2.0L DOHC i-VTEC I gasoline engine.

* The 2-litre DOHC i-VTEC I integrates the i-VTEC system which uses the VTEC  and VTC which uses a direct injection system for an air-fuel ratio of up to 65:1 for an unprecedented level of ultra-lean combustion. Stable combustion is achieved by using less fuel than conventional direct injection engines which have an air-fuel ratio of 40:1.
* Combustion control through the use of high-precision EGR valves and a newly developed high-performance catalyst enable the 2.0 litre DOHC i-VTEC I lean-burn direct injection engine which qualify as an Ultra Low Emissions Vehicle.