What is VTEC and How Does it Work?
Few automotive terms reach the cult-like obsession from fans like Honda’s VTEC technology. From tuner forums to mainstream automotive media, VTEC is widely known for being the original variable valve timing technology, as well as eliciting surprised reactions from passengers as it kicks in with its iconic high RPM scream.
VTEC not only revolutionized performance cars, it helped Honda cement itself as a legendary name in the tuning scene. The Civic and Integra were considered legitimate performance machines with the right upgrades, which pushed these models ahead of their competitors and gave Honda a “cool factor” that they hadn’t seen in the U.S. prior.
What is VTEC
VTEC is Honda’s proprietary variable valve timing (VVT) technology. VVT is any system that can dynamically alter engine timing, usually based on the RPM of the motor. This allows for both increased fuel economy and performance, as the engine can run at an efficient cam profile at lower RPMs and switch to a more aggressive profile when in the higher rev range.
The primary idea of variable timing is that one engine can essentially have the properties, performance, and efficiency of two different engines. At lower RPMs, VVT motors can sip gas like a commuter vehicle. At higher RPMs, they can kick into a different “mode” where performance is the focus.
Born in the early 1980s within Honda’s motorcycle engineering teams, VVT was first seen on a consumer car in the Japanese market in 1985. This was the proof of concept Honda needed to pursue the use of VVT beyond their home country.
The 1989 Honda Integra saw the first widespread introduction of VTEC in a consumer vehicle, but never made it to American shores. North America’s first taste of VTEC came in the form of the 1991 Acura NSX, and then more affordably in the 1992 Acura Integra GS-R.
VVT quickly proved itself as more than an interesting gimmick. There was just something to that visceral driving experience that competing vehicles couldn’t replicate at this point. Other manufacturers took notice and followed suit with their version of variable timing. German heavyweight BMW introduced VANOS in 1992, with Nissan, Ford, and Toyota jumping on the bandwagon in the late 90s.
While other systems accomplished variable timing through similar methods, VTEC still maintained certain things that made it unique.
How Does VVT & VTEC Work?
To understand how any variable valve timing system works, it’s crucial to first understand these components.
Valve: Valves are the “doors” that open and close to regulate the air/fuel mixture being introduced to the combustion chamber, as well as the expulsion of exhaust.
Rocker arms: Rocker arms are the levers that the cams push against. These levers are what open and close the valves.
Cam: Cams are oblong wheels that push against the rocker’s arms to actuate the valves. The “profile” of the cam lobe directly affects the duration that the valves are opened and the extent to which they open.
Camshaft: Camshafts are the rods that the cams themselves are attached to. As the camshaft spins, so do the cams.
Other Basic VVT Systems
Traditional VVT systems alter timing by shifting the phase angle of the camshafts. As the camshaft changes angle, it pushes the rocker arms farther and longer, which allows the valves to open farther and longer.
Most VVT systems use oil pressure to alter the phase angle. As engine RPMs increase, so does oil pressure, forcing the VVT system to actuate. For instance, BMW’s VANOS uses a solenoid to direct oil pressure to push a piston, which in turn moves a helical gear that controls the camshaft’s phase angle.
As these systems continuously change the camshaft’s profile, the effect of VVT isn’t that noticeable when it first kicks in and gradually becomes more aggressive as the RPM climbs.
VTEC
VTEC, on the other hand, uses separate cams with different profiles. Instead of just changing the angle, the actual cam itself is switched to a high-performance profile. The high-performance cams are spinning freely when not engaged. When the vehicle climbs above a certain rev range, a pin is hydraulically inserted into the low-RPM rocker arm(s) that locks and engages the high-performance cam profile. Since the engine is now operating on a separate cam profile entirely, it allows for the lift of the cams to be changed along with the timing, allowing for increased air and fuel to enter the cylinders.
Other manufacturers have since also introduced variable valve lift (VVL) technology to their engines, such as BMW’s Valvetronic, but VTEC does not need a separate system.
One of the largest differences between most VVT and VTEC is the difference in how they engage. Other variable timing systems change the cam profile continually in relation to the RPM, which gives it a gradual power increase as VVT engages. Since VTEC only uses two (occasionally three) profiles that switch at a specific point in the rev range, VTEC engagement causes a distinct jolt that has also become one of its most iconic attributes.
This visceral feeling is part of what made VTEC such an enjoyable feature for Honda owners, leading to its popularity among those looking for an engaging driving experience at a commuter car price point. At the dawn of the Internet age, VTEC became a phenomenon among enthusiasts and became widely known for the sound and feel of it “kicking in” when accelerating.
i-VTEC
“Intelligent-VTEC”, otherwise known as i-VTEC, is Honda’s VTEC system combined with a traditional continuous cam phaser system. While still generally limited to two distinct cam profiles, the computer-controlled cam phasing allows for finer adjustments to be made continually based on RPM and engine load (with the ability to advance the timing by 25-50 degrees depending on the motor). Timing is fully retarded (opposite of advanced) at idle, which allows for stellar fuel-efficiency, and runs at a slightly advanced profile during low-RPM to full-throttle driving.
Past 2002, most Honda four-cylinder motors sold in America began to use some variation of i-VTEC.
Honda & Acura Service in Tucson
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