Most gearheads know the name “VTEC”, but many are unaware of how it actually works. VTEC, a system implemented in many Honda engines, stands for Variable Valve Timing and Lift Electronic Control. This mechanism alters valve timing, duration, and lift to provide optimized performance at higher RPMs.

The first engine fitted with VTEC was on the 1989 Honda Integra XSi. The design, which featured two cam profiles per valve, resulted in the highest horsepower per liter density in its class. In contrast to typical cam phasers, the VTEC operates with an iterative method of switching between multiple cam profiles.

Many automakers sought to provide their own interpretations of VTEC, investing multiple years of research and development to achieve the feat. Let’s learn more about the mechanics of VTEC and how it provides increased efficiency and smoother power.

Evolution Of VTEC

Honda VTEC Variable Valve Timing Performance Engine Explained Tech
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The first form of valve control on a Honda product was the "REV" system, or revolution modulated valve control. This system was seen on the 1983 CBR400F sportbike and employed independent intake valves that were idle until the demand for power increased. Honda released the New Concept Engine project in 1984, marking the origins of VTEC.

The first VTEC engine was fitted to the 1989 Honda Integra XSi. This car was only sold in Japan; American consumers will remember the first VTEC as the 2000 Acura NSX. In 1999, Honda released the HYPER VTEC valve control system for 4-stroke motorcycle engines. Along with increasing high-speed performance, it claimed to boost fuel efficiency by approximately 6.6%. This system allowed two valves to function initially; when more power was needed, the additional intake and exhaust valve activates.

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Components Of The System

Honda VTEC Variable Valve Timing Performance Engine Explained Tech
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A VTEC engine has individual profiles for each camshaft. Two lower-profile cams are located on either side of a high profile cam, each with a dedicated rocker arm. The larger central cam is supported by a "Lost Motion Assembly". The Lost Motion Assembly is a preloaded spring that provides tension to the cam so that rattle is not produced during normal operation.

The VTEC solenoid modulates oil pressure sent to locking pins ("VTEC eliminators") that engage or disengage the center rocker arm.  Upgraded pins are available to further boost the performance of the system, such as those made of titanium.  Most VTEC systems were used in DOHC (dual overhead camshaft engines) but have seen some use in SOHC engines as well.

How It Actually Works

Honda VTEC Variable Valve Timing Performance Engine Explained Tech
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The primary objective of the VTEC system is to improve fuel efficiency at lower RPMs and boost performance at higher RPMs. This means providing extra fuel and air to the engine at higher speeds. When the RPM threshold is reached, a 12V signal is sent to the VTEC solenoid.

The oil pressure sent through the system forces the pins to move, allowing the center cam to function. Activation of the high-performance lobe results in better lift and longer duration. When speed is reduced, the pins retract again to disengage the center rocker arm allowing the two low profile cams to work alone.  In addition to the benefits that arise from variable valve control and timing, the mechanics of the system allow the fuel to swirl in a manner that maximizes combustion.

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Versions Of The VTEC System

Honda VTEC Variable Valve Timing Performance Engine Explained Tech
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Many automakers released some sort of variable valve control system in the years following the VTEC's release. Honda's technology is unique in that it works with both timing and lift on both the intake and exhaust. Toyota's VVT-i, for example, results in different valve timing on the intake alone.

Honda has released a few different types of the VTEC system which are all built on the same principle. VTEC-E makes use of two cams with different sizes. In a “3-stage VTEC”, there are two VTEC solenoids; Valve lift, duration, timing, and size are all modulated by this system. An example of a 3-stage VTEC can be seen in the D15B SOHC engine on models including the 92-95 Honda Civic VTi.

As with any engine technology, problems can arise from the VTEC system. Fortunately, most of these are relatively easy to fix. Certain oil leaks and reduced performance can be due to the gasket on the VTEC solenoid failing over time. Since the engine’s components are easy to work on, replacing the gasket or the solenoid itself is a quick task. Moreover, most parts for a Honda or Acura are easy to find.

More recently, Honda introduced the i-VTEC, or "intelligent" VTEC which incorporates computer management of the system and a hydraulic drive. VTC, or Variable Timing Control, is also included in this system. Camshaft phasing in this system is continuously variable and allows for a 50º range of phasing depending on demand.

Honda published a patent for an advanced VTEC system that has yet to be released. This is an upgrade to the technology that allows the phases to respond to power demand regardless of the engine speed. VTEC was and continues to be an unequaled technology with incredible potential for the future.

Sources: Honda Global, Super Street Online, Civic EG

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