🚗 The Unfinished AVTEC Technology: Honda’s Continuously Variable Valve Lift System
🚗 【Technical Feature】The Unfinished AVTEC Technology: Honda’s Continuously Variable Valve Lift System
Original: Honda Magazine | Japanese Car Enthusiast Magazine | October 2, 2024, 14:21
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🔍 Introduction to VTEC’s Legacy
The VTEC system, first introduced in 1989 with the B-series engines, has evolved over the years with various adaptations for different purposes and performance levels. The original full name of the first generation VTEC was DOHC VTEC. Over subsequent years, Honda’s engineers developed a range of VTEC systems:
SOHC VTEC (Single Overhead Camshaft VTEC)
VTEC-E (Economy-focused VTEC)
Three-stage VTEC balancing performance
i-VTEC, introduced in 2001, which integrated the VTC (Variable Valve Timing Control) into the camshaft mechanism, enabling adjustable timing and lift
VTEC Turbo (e.g., K20C)
Among these developments lies the powerful yet never-implemented AVTEC system, an intriguing piece of Honda’s engineering legacy.
✨ What is AVTEC?
The “A” in AVTEC stands for Advance, signifying a continuously variable VTEC system. Traditionally, to vary valve lift at different RPMs, Honda engineers used three cam lobes with different lift heights and durations on the camshaft of each cylinder. A rocker arm mechanism between the camshaft and valves, controlled by oil pressure, would engage different lobes at specific RPMs, enabling greater valve lift for high-RPM performance. This is the basic principle of traditional VTEC systems.
Even as VTEC technology evolved, the mechanism remained largely unchanged. SOHC VTEC was an early variation where one camshaft controlled intake and exhaust valves with VTEC rockers. VTEC-E was a simpler, fuel-efficient version allowing one intake valve to open partially while the other opened fully. The K20A engine in the Integra Type-R (DC5) introduced the i-VTEC, adding VTC for adjustable valve timing. The black-top and red-top variants of K20A differed, with the red-top featuring VTEC on both intake and exhaust camshafts, while the black-top had VTEC only on the intake side.
🛠 The Mechanics of AVTEC
Unlike the traditional VTEC systems that use a rocker arm mechanism with pins and oil pressure to switch between cam lobes, AVTEC simplifies this process. The complex rocker arm system is replaced with a mechanism resembling a camshaft sleeve that wraps around the camshaft and can rotate independently. A slider of variable thickness engages the camshaft to change valve lift seamlessly. The slider’s thickness changes dictate the contact point with the rocker arm, adjusting valve lift as required.
🔹 Low vs. High RPM Operation:
At low RPMs, the thinnest part of the slider contacts the rocker arm, minimizing valve lift.
As engine speed increases and greater air intake is needed, the sleeve mechanism rotates (clockwise in diagrams), maintaining continuous contact with the rocker arm. The slider’s thickness varies, enabling a gradual increase in valve lift. When the thickest part of the slider engages, valve lift is maximized, allowing the most air intake.
📈 AVTEC's Potential Impact
Described in 2006, AVTEC promised significant advancements. Although Honda did not specify power output figures, they highlighted environmental benefits: fuel consumption reduced by 13% and emissions lower by 25% compared to Japan’s 2005 standards when applied to the K24A engine. Notably, promotional material featured a red-lettered engine cover, reminiscent of the 200 HP K24A used in the Accord 24S. This sparked curiosity—would AVTEC enhance horsepower? Could its seamless valve actuation make torque delivery more linear?
🤔 Where is AVTEC Today?
Despite its promise, AVTEC has yet to be implemented in production vehicles. Likely due to practical issues, this system remains shelved. Whether as a strategic technology reserve or a potentially practical system, enthusiasts hope AVTEC may one day see the light of day.
Original: Honda Magazine | Japanese Car Enthusiast Magazine | October 2, 2024, 14:21
🌟 Hello, my friend... Welcome to a hidden gem—OLD FISHER DISCOUNT, your one-stop online shop with 7,000+ unique finds waiting for you. 🎉
🛒 Explore a World of Discoveries Dive into our collection and uncover special treasures that will delight and inspire.
🔗 Start Your Journey Here: www.fisherdiscount.com
Come and see why we’re more than just a shop; we’re a place of endless possibilities! ✨
🔍 Introduction to VTEC’s Legacy
The VTEC system, first introduced in 1989 with the B-series engines, has evolved over the years with various adaptations for different purposes and performance levels. The original full name of the first generation VTEC was DOHC VTEC. Over subsequent years, Honda’s engineers developed a range of VTEC systems:
SOHC VTEC (Single Overhead Camshaft VTEC)
VTEC-E (Economy-focused VTEC)
Three-stage VTEC balancing performance
i-VTEC, introduced in 2001, which integrated the VTC (Variable Valve Timing Control) into the camshaft mechanism, enabling adjustable timing and lift
VTEC Turbo (e.g., K20C)
Among these developments lies the powerful yet never-implemented AVTEC system, an intriguing piece of Honda’s engineering legacy.
✨ What is AVTEC?
The “A” in AVTEC stands for Advance, signifying a continuously variable VTEC system. Traditionally, to vary valve lift at different RPMs, Honda engineers used three cam lobes with different lift heights and durations on the camshaft of each cylinder. A rocker arm mechanism between the camshaft and valves, controlled by oil pressure, would engage different lobes at specific RPMs, enabling greater valve lift for high-RPM performance. This is the basic principle of traditional VTEC systems.
Even as VTEC technology evolved, the mechanism remained largely unchanged. SOHC VTEC was an early variation where one camshaft controlled intake and exhaust valves with VTEC rockers. VTEC-E was a simpler, fuel-efficient version allowing one intake valve to open partially while the other opened fully. The K20A engine in the Integra Type-R (DC5) introduced the i-VTEC, adding VTC for adjustable valve timing. The black-top and red-top variants of K20A differed, with the red-top featuring VTEC on both intake and exhaust camshafts, while the black-top had VTEC only on the intake side.
🛠 The Mechanics of AVTEC
Unlike the traditional VTEC systems that use a rocker arm mechanism with pins and oil pressure to switch between cam lobes, AVTEC simplifies this process. The complex rocker arm system is replaced with a mechanism resembling a camshaft sleeve that wraps around the camshaft and can rotate independently. A slider of variable thickness engages the camshaft to change valve lift seamlessly. The slider’s thickness changes dictate the contact point with the rocker arm, adjusting valve lift as required.
🔹 Low vs. High RPM Operation:
At low RPMs, the thinnest part of the slider contacts the rocker arm, minimizing valve lift.
As engine speed increases and greater air intake is needed, the sleeve mechanism rotates (clockwise in diagrams), maintaining continuous contact with the rocker arm. The slider’s thickness varies, enabling a gradual increase in valve lift. When the thickest part of the slider engages, valve lift is maximized, allowing the most air intake.
📈 AVTEC's Potential Impact
Described in 2006, AVTEC promised significant advancements. Although Honda did not specify power output figures, they highlighted environmental benefits: fuel consumption reduced by 13% and emissions lower by 25% compared to Japan’s 2005 standards when applied to the K24A engine. Notably, promotional material featured a red-lettered engine cover, reminiscent of the 200 HP K24A used in the Accord 24S. This sparked curiosity—would AVTEC enhance horsepower? Could its seamless valve actuation make torque delivery more linear?
🤔 Where is AVTEC Today?
Despite its promise, AVTEC has yet to be implemented in production vehicles. Likely due to practical issues, this system remains shelved. Whether as a strategic technology reserve or a potentially practical system, enthusiasts hope AVTEC may one day see the light of day.
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