- VTEC® was the first commercially successful variable valve timing and lift technology used in a production car
- VTEC has evolved over the past 30+ years to provide multiple benefits, including increasing horsepower and torque, and improving fuel efficiency
- The technology remains a key component to Honda’s enthusiast appeal
Variable Valve Timing and Lift Electronic Control, or VTEC®, debuted in the late 1980s as a way to extract maximum horsepower and torque from smaller displacement engines without using turbocharging. As the first practical, reliable and commercially successful variable valve timing and lift technology, VTEC spurred an industry-wide movement to use variable valve timing in engines.
Today, VTEC has evolved to include specialized applications designed to improve fuel efficiency and emissions, as well as add power. Originally an alternative to turbochargers, today VTEC is used in conjunction with turbos for maximum responsiveness and power, all while helping vehicles meet strict emissions and fuel economy standards in the U.S. and around the world.
VTEC History
In 1984, Honda launched the New Concept Engine (NCE) program to increase the horsepower and torque produced from its small displacement engines. The program led to the development of 4-valve per cylinder double overhead cam (DOHC) engines that debuted in Honda and Acura automobiles at the time, including the 1986 Acura Integra in the U.S
Traditionally, high-revving four-valve-per-cylinder engines sacrificed low-end torque to produce high-revving horsepower. The intricate relationship between the timing, lift, and duration of intake and exhaust valves set to produce high-revving horsepower generally hurts low-end torque. Resetting the valvetrain and retuning an engine for low-end torque would do so at the expense of high-end horsepower.
Ikuo Kajitani, a Honda engineer at Honda's Tochigi R&D Center, recognized that the solution to this problem was to create a mechanism that could alter the timing and lift of the valves so low-end torque wouldn’t be sacrificed for high-end power, or vice versa. This led to the development of Variable Valve Timing and Lift Electronic Control, or VTEC.
VTEC Fundamentals
At the core of early VTEC engines was a camshaft featuring three different cam lobes for each pair of valves. The two outer cams were tuned for low-end torque and smooth idle, while the center cam was tuned for high-revving horsepower. Each cam had its own rocker arm, but only the outer two actually pressed against the valves, with the central rocker arm assigned only to the center cam.
At low engine speeds, the two outer cams were used to open and close the valves, with the center cam inactive, since its rocker arm wasn’t directly attached to the valvetrain. However, as revs increased, the engine computer signaled a spool valve to direct oil pressure to activate a pin that locked the two outer rocker arms to the arm in the center. This forced the two outer arms to act upon the center cam, which featured a longer duration, higher lift, and timing optimized for high-end horsepower.
VTEC made its commercial debut on the 1989 Honda Integra XSi in Japan, with stunning results. Active on both the intake and exhaust cams of this DOHC 1.6-liter engine (B16A), it produced 160 horsepower at an incredible 7,600 rpm. The broad torque curve peaked at 111 lb.-ft. at 7,000 rpm, but offered most of that torque well below that lofty figure. A short time later, VTEC was introduced on the 1991 Acura NSX, which developed 270 horsepower and 210 lb.-ft. of torque from its 3.0-liter V6 engine (C30A).
Multiple variations of VTEC have been created over the decades to improve horsepower and torque while lowering emissions and increasing fuel efficiency. The various permutations include VTEC-E, i-VTEC with Variable Cylinder Management™ (VCM®), pairing VTEC with turbochargers, and i-VTEC with Variable Timing Control™ (VTC™).
VTC, while strictly not VTEC since it doesn’t alter the lift or duration of the valves, has often been used together with VTEC since VTC was Introduced in the early 2000s. VTC uses a spool to direct high-pressure oil to chambers inside a cam’s drive sprocket, allowing for continuous adjustments of the intake camshaft’s position relative to the crankshaft.
Known as “phase,” this position could be adjusted over a wide range, depending on engine load and other factors, allowing extremely precise control of valve timing over the engine’s entire operating range. When combined with VTEC, VTC allows the optimal balance of power delivery, fuel efficiency and exhaust emissions.
DOHC VTEC
The original DOHC version of VTEC helped establish Honda as a performance icon in the 1990s. The iconic nature of VTEC is due in part to the dynamic of driving cars equipped with DOHC VTEC. At low RPM, the engines are docile and quiet, but when the VTEC system crosses to its higher RPM cam – that is, when “VTEC kicks in,” as the high-lift switchover has become known – the engine note takes on a sharper edge, with an increase in power that’s immediately noticeable from behind the wheel.
The first Honda-branded vehicle in the U.S. to use a DOHC version of VTEC was the 1993 Honda Prelude VTEC. The 2.2-liter DOHC 16-valve 4-cylinder (H22A1) boasted 190 hp and 158 lb.-ft. of torque. Working much like the VTEC mechanism on the NSX, it produces an additional 30 horsepower compared to the 2.3-liter non-VTEC engine in the Prelude Si (H23A1). On the Prelude VTEC, both the intake and exhaust cams use the cam-switching technology, with low-profile cams used at low RPM for better torque delivery and efficiency. At 4,800 RPM, VTEC locks the rocker arms to the high-RPM cam. The fifth-generation Prelude sold from 1997 through 2001 was powered solely by an updated version of the 2.2-liter VTEC engine (H22A4) with 200 hp and 156 lb.-ft. of torque.
In 1994, the Honda Del Sol hardtop convertible was equipped with DOHC VTEC as well, with a new 1.6-liter engine (B16A3). Producing 160 hp and 111 lb.-ft. of torque, the Del Sol’s engine had a specific output of 100 horsepower per liter, all without the use of turbocharging. Especially considering the low price of the Del Sol VTEC, this was an incredible feat for the time, and still impressive today. A version of this engine with the same output (B16A2) powered the 1999-2001 Civic Si.
The final engine to use this original DOHC VTEC configuration was the 2000 Honda S2000 sports car. Its 2.0-liter DOHC 4-cylinder engine (F20C) produces 240 HP and 152 lb.-ft. of torque, and features a 9,000 rpm redline. The resulting specific output of 120 horsepower per liter, without turbos, is more commonly associated with exotic cars costing hundreds of thousands of dollars. It was replaced for the 2004 model year with a 2.2-liter version (F22C1) that produced the same power, but with a 10 lb.-ft. torque improvement and the redline lowered to 8,000 rpm.
These DOHC VTEC engines were fundamental to the explosion of aftermarket performance parts for Japanese cars in the 1990s, and key to Honda’s dominance in that market. Honda was able to match the power output of competitors without complicated and heavy turbocharging, while still offering excellent drivability and fuel efficiency.
SOHC 4-Cylinder VTEC
The single overhead camshaft (SOHC) version of VTEC first appeared on Honda-branded vehicles in two very different forms with the introduction of the fifth-generation Civic family in 1992. On the Civic Si hatchback and Civic EX sedan, VTEC was used to increase horsepower to excellent effect. However, the potential for VTEC to go beyond its origins as a power-maker were first realized with the fuel-sipping Civic VX hatchback, which used a special fuel-efficiency focused version called VTEC-E (see below).
The 1.6-liter SOHC 4-cylinder engine in the Civic Si and EX (D16Z6) use VTEC to alter the timing and lift of just the intake valves. The exhaust valves use a fixed profile. At low and medium engine speeds, the two outer cam lobes on the intake valves use a mild profile, with the timing for the two intake valves slightly out of phase to help generate swirl for efficient combustion.
At about 5,000 rpm rocker arms lock to the center cam lobe, which is tuned to optimize high-RPM power. This use of VTEC increased output from 108 hp and 100 lb.-ft. in the non-VTEC 1991 Civic Si (D16A6), to 125 and 106 in the VTEC-enhanced 1992 model. Fuel economy ratings also increased from 28 mpg city and 32 mpg highway, to 29 mpg city and 36 mpg highway.
In 1994, VTEC debuted in the Accord family, with a SOHC system featured on the Accord EX Sedan, Coupe and Wagon. Operationally similar to the system used on Civic Si and EX, the Accord’s 2.2-liter 4-cylinder (F22B1) produced a peak of 145 horsepower, 20 more than the non-VTEC versions of the engine (F22A1) used in LX models.
Throughout the 1990s, and into the early 2000s, 4-cylinder SOHC VTEC remained a staple in Honda sedans, appearing in top-line Civic and Accord models and providing the dual benefits of improved horsepower and torque, while still receiving excellent fuel economy ratings.
VTEC-E
While the 1992 Civic Si and EX Sedan used VTEC to add power, the 1992 Civic VX introduced VTEC-E, a version of the technology focused on improving fuel efficiency. Below 2,500 rpm, VTEC-E operates the 16-valve 1.5-liter SOHC engine (D15B5) in a 12-valve mode, with one intake valve remaining mostly closed. This single intake-valve operation enhances swirl inside the combustion chamber, creating a stratified charge that concentrates the more fuel-rich part of the mixture near the spark plug for better fuel efficiency. Above 2,500 rpm, the inactive valve and active valve are linked, creating a true 16-valve engine for more power.
Combined with lean-burn technology, VTEC-E made a dramatic difference in fuel economy ratings. Civic VX’s EPA-estimated fuel economy rating of 48 mpg city and 57 mpg highway was superior to the lighter 1991 Honda CRX HF (49/52), while boasting a 30-horsepower advantage over the small two-seater.
VTEC-E returned for the sixth-generation Civic in the Civic HX, which featured a larger 1.6-liter engine (D16Y5) boasting a significant power increase from 90 hp to 115 hp. Even with the larger displacement and greater emphasis on power, EPA fuel economy ratings still topped the Civic line with 39 mpg city and 45 mpg highway when equipped with the 5-speed manual transmission.
Although no longer explicitly called VTEC-E, multiple engines continued to use this type of VTEC mechanism, including the sixth-generation (1998-2002) Honda Accord EX and LX with the 2.3-liter 150-horsepower 4-cylinder engine (F23A1). It was also used on the SOHC 3.0-liter V6 engines in that same generation of Accord (J30A1), as well as the 3.5-liter V6 in the second-generation Honda Odyssey (J35A1, J35A4) and first-generation Honda Pilot (J35A4).
i-VTEC
Implemented in the early 2000s, i-VTEC is still in use today. i-VTEC refers to a more intelligent version of VTEC that incorporates tighter computer integration to the valvetrain mechanism.
Although i-VTEC is used in both 4-cylinder and V6 engines, the details in each application differ. In Honda 4-cylinder engines i-VTEC uses a combination of the variable cam lift and duration of VTEC along with Variable Timing Control™ (VTC™). Honda V6 engines feature i-VTEC with Variable Cylinder Management™ (VCM®) to maximize fuel efficiency.
DOHC 4-Cylinder i-VTEC with VTC™
For the 2002 model year, VTEC was reengineered to incorporate Honda’s new Variable Timing Control (VTC) on the exhaust cam of DOHC VTEC engines. The technology debuted in the 200-hp Acura RSX Type S (K20A2), and the 160-hp Acura RSX and Honda Civic Si (K20A3). Both engines use the cam-switching feature of the original VTEC engines, however, the K20A3 use it solely on the intake cam, while the K20A2 use it on both intake and exhaust cams. In 2006, a high-output version of this engine powered the eighth-generation Honda Civic Si Coupe and Sedan (K20Z3).
Larger 2.4-liter versions of this engine featured similar horsepower output, but additional torque, and debuted in the 2002 Honda CR-V (K24A1) and 2003 Honda Accord and Element (K24A4). Throughout the 2000s and much of the 2010s, variations of this 2.4-liter engine, improved through the use of direct-injection under the Earth Dreams™ name, were the standard 4-cylinder powerplant in many of Honda’s passenger cars and compact SUVs. A high-performance variant (K24Z7) debuted in the ninth-generation Civic Si Sedan and Coupe, initially with 201 hp, and later 205 hp.
Employed on both the 10th and the current 11th-generation Civic, the standard 2.0-liter engine (K20C2) features an i-VTEC system that uses VTC on both the intake and exhaust cams, and VTEC on the intake cam. The use of VTC on both cams adds another layer of efficiency and control to combustion, allowing precise timing of valve opening and closing for improved power and a smooth idle.
SOHC V6 i-VTEC with VCM®
Fuel efficiency has always been a Honda hallmark, and in 2005 VTEC was again modified with a new technology, Variable Cylinder Management™ (VCM®). Depending on throttle position, speed, and engine load, VCM shuts down half of the cylinders turning a V6 into an inline-3 cylinder.
Although also called i-VTEC, the system used on the V6 engines does not include a cam-phasing mechanism as on four-cylinder application. Introduced in the 2005 Honda Odyssey EX-L and Touring grades (J35A7), i-VTEC with VCM features traditional VTEC cam-switching for low-end torque and high-end horsepower combined with the added benefit of shutting down the engine’s rear bank of cylinders to increase fuel efficiency in certain driving situations.
When under light load, VTEC switches these cylinders to a cam with zero lift, closing the intake valves completely. This, along with cutting fuel to the injectors on the affected cylinders, shuts them down almost completely; the spark plug continues to fire to maintain heat in the plug for when the cylinders are restarted. Since then, VCM has appeared on multiple V6-powered Honda vehicles, including the current generations of Odyssey, Pilot, Passport and Ridgeline.
For the eighth-generation Honda Accord (2008-2012), VCM was implemented on both banks of cylinders and expanded to a three-mode operation. Depending on driving conditions, the engine switches between full 6-cylinder operation, to shutting down the engine’s rear bank of cylinders to operate as a 3-cylinder, and adds a 4-cylinder mode that alternates between firing different pairs of cylinders on each bank.
With the introduction of the ninth-generation Accord for the 2013 model year, VCM returned to two-mode operation, making the eighth-generation Accord the only Honda to use three-mode VCM.
VTEC Turbo
Using variable valve timing and lift with a turbocharger presents unique opportunities for generating power and improving fuel efficiency, and for the 2016 model year Honda began combining these technologies in multiple ways.
The 174-hp 1.5-liter turbocharged 4-cylinder engine that debuted in the 2016 Civic (L15B7), along with the more powerful 190-hp version powering the 2017 CR-V (L15BE VTC™ Turbo), incorporated dual VTC, allowing optimal cam timing on both the intake and exhaust to suit driving conditions. Under light loads, valve overlap can be increased to reduce pumping losses and improve fuel efficiency. When engine speed is low and engine load is high, such as during initial acceleration, the amount of overlap is increased to boost the scavenging effect, which improves torque and responsiveness. When engine speed is high and engine load is also high, such as during full-throttle acceleration, the amount of valve overlap is reduced to increase engine output. However, neither of those engines use the variable valve-lift technology of VTEC.
VTEC, VTC and turbos were combined in the U.S. market for the first time in the 306-horsepower 2.0-liter turbocharged 4-cylinder (K20C1) powering the Civic Type R in 2017. Civic Type R uses VTEC to alter the timing, lift and duration of the exhaust valves, plus uses VTC to independently control the timing on the intake and exhaust cams.
As with the turbocharged Civic and CR-V, the dual VTC system allows exceptionally precise control of valve timing on the intake and exhaust for improved power and fuel efficiency. At low engine speeds at wide-open throttle, the exhaust uses the low-lift cam, while VTC is used to advance the intake and delay the exhaust timing. This high-overlap combination results in optimum scavenging at low speeds. At high engine speeds and wide-open throttle, VTEC switches to the high-lift cam, while VTC reduces overlap as much as possible, reducing pumping losses. The result is excellent boost response at all engine speeds, and outstanding high-RPM power.
Both engines introduced in the 10th-generation Honda Accord also combine turbocharging, VTC and VTEC. The Accord’s 1.5-liter turbo (L15BE VTEC Turbo) is similar to the engine in the CR-V, but with the addition of VTEC to the exhaust cam side. This results in a 13 lb.-ft. increase in torque versus CR-V (192 lb.-ft. vs. 179 lb.-ft.), and across a broader area, with the Accord’s torque peak coming 400 rpm earlier (1600 rpm vs 2000 rpm). Related to the engine in the Civic Type R, the Accord’s 2.0-liter 4-cylinder (K20C4) uses the combination of turbocharging, VTC and VTEC in a similar fashion.
For the 11th-generation Civic, VTEC returned to the exhaust cam on the 1.5-liter turbocharged 4-cylinder (L15B7 VTC Turbo) used in Sedan EX and Touring grades, and Hatchback EX-L and Sport Touring grades. The addition of VTEC helps the engine equal the output of earlier non-VTEC versions in the 10th-generation Civic Hatchback Sport and Sport Touring without requiring premium fuel. VTEC is also used on the 2022 Civic Si Sedan, helping produce a broader torque curve, a lower rpm torque peak, and sustained power at higher rpm.
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