The i-VTEC vs. Honda VTEC. VTEC is simply Honda’s euphemism for variable valve timing technology. It is comparable to BMW’s Vanos and Toyota’s VVT-i systems. VTEC is an abbreviation for Variable Timing Electronic Control.
Honda, on the other hand, has two variants of this technology: i-VTEC and VTEC-E. They are all variable valve timing and lift systems, but they operate in a slightly different manner. This guide will go over the differences between VTEC, i-VTEC, and VTEC-E, as well as provide a high-level understanding of variable timing and the benefits it provides Honda engines.
What exactly is variable timing and lift?
VTEC and other variable valve technologies have two components: variable timing and variable lift. Both terms refer to an engine’s valves opening and closing. Variable lift is in charge of driving higher performance, while variable timing is in charge of emissions and engine temperature control.
On variable lift engines, the camshaft has two cam “profiles” or two sets of lobes, low-lift and high-lift. Low-lift, as the name implies, has smaller lobes, which means the valves do not open as far. High-lift valves have larger lobes, allowing the valves to open further and thus allow more air into and out of the combustion chamber. The low-lift cam profile is engaged during normal driving. When driving aggressively or opening the throttle wider, a solenoid switches over to the high-lift cams, increasing valve travel and performance.
Valve timing refers to when the valves open and how long they remain open. Variable timing enables the engine to control when and how long the valves open under various operating conditions. It thus controls the air-to-fuel ratios in the cylinder because it controls how much air enters the cylinder, which influences emissions, engine temperatures, and fuel economy.
When both of these technologies are combined into a single system, such as VTEC, you get more power and better control over power curves, all while lowering emissions and improving fuel economy. This is a very basic explanation and there are dozens of ways of implementing VVT and VVL, so check out this in-depth video if you want to learn more.
What Is VTEC and How Does It Work?
VTEC is an abbreviation for Honda’s variable valve timing and variable valve lift technology.
A VTEC engine has two sets of cam profiles and two different rocker arms for each valve. As previously stated, there are low-lift and high-lift cam profiles. The distinction with VTEC compared to other variable timing systems is in the rocker arm design. Each valve has a low-cam rocker arm as well as a high-cam rocker arm. The low-cam rocker arms each control one valve, while the high-cam rocker arms each control two valves. Because it sits between the two low-cam rocker arms, the high-cam rocker is also known as the central rocker arm.
As RPMs rise, so does oil pressure, causing the central rocker arm to force a piston outward, locking the two outer rocker arms to the central rocker arm. As a result, the outer rocker arms, which are connected to the valves, will now move in tandem with the central rocker arm, which has a higher lift.
Almost all Honda engines are dual overhead cam (DOHC), which means that the intake and exhaust valves each have their own camshafts. As a result, VTEC can be enabled on both the intake and exhaust valves, or just one. For example, turbocharged Honda engines will only have VTEC on the exhaust valves and only one cam profile on the intake valves.
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The Advantages of VTEC
Honda VTEC systems have several notable advantages, including:
- Engine power is increased at higher RPMs.
- Improved low-end torque
- Enhanced engine efficiency
- Emissions reductions
- Improved fuel economy
Overall, VTEC provides the best of both worlds and is excellent technology. It’s difficult to argue with something that improves performance, efficiency, emissions, and fuel economy all at once.
What exactly is i-VTEC?
If variable valve timing isn’t complicated enough for you, Honda has added i-VTEC, which stands for Intelligent VTEC. It was introduced by Honda in 2001 and has since been used in virtually all of their performance engines.
The above-mentioned design is used by traditional VTEC engines. Only the lift and duration provided by the two different camshaft lobes or profiles can be used to control timing in this system. To gain more control over valve timing, Honda developed and integrated what is known as VTC with VTEC, which is known as i-VTEC.
VTC stands for variable timing control, and it allows the camshaft to be advanced or retarded to control valve overlap. Traditional VTEC engines only opened the exhaust valve after the intake valve had completely closed, so the two valves were never open at the same time. VTC changes the angle of the camshaft lobes, allowing the valves to overlap or be open at the same time. Its variable nature allows it to be adjusted at various RPM levels.
So, what is the distinction between VTEC and i-VTEC?
i-VTEC adds additional valve timing control by allowing camshaft angle adjustments. To maximize performance at low and high RPMs, the valves must open and close in different ways for each RPM range. The primary difference between VTEC and i-VTEC is that VTEC does not do this.
In comparison to traditional VTEC, i-VTEC provides a smoother power band and improved performance at both high and low RPMs.
What exactly is VTEC-E?
VTEC and i-VTEC are both performance-oriented systems. They are designed to increase upper RPM horsepower. While they are intended to improve fuel economy, increasing horsepower and fuel economy do not necessarily go hand in hand. As a result, we have VTEC-E, where the E stands for Efficiency.
VTEC-E is a fuel-efficient version of VTEC that is more concerned with fuel economy than with power. It is primarily on Honda hybrid and fuel-efficient vehicles.
To improve fuel economy, it shuts off intake valves at low RPMs. On a standard 16-valve engine, for example, each cylinder has two intake valves. VTEC-E engines disable one of the intake valves, leaving it mostly closed, converting the engine to a 12-valve engine. When one valve is closed, less space is available for air to enter the combustion chamber, causing it to enter the engine faster, atomizing the fuel better and causing it to burn more efficiently. This is known as a lean burn, and it increases air-to-fuel ratios, which increases fuel economy.
VTEC-E improves fuel economy at the expense of power and performance. Honda did, however, develop what is known as a 3-stage VTEC, which combines both traditional VTEC and VTEC-E to provide better low-end fuel economy while still providing high-end performance. Due to the complexity of the valvetrain, 3-stage VTEC engines are extremely rare and are no longer used.
Finally, VTEC-E is Honda’s fuel-efficient version of variable valve timing technology. By turning off one intake valve for each cylinder, it effectively converts a 16-valve engine to a 12-valve engine. This improves the oxidation of the fuel, increasing its combustibility and allowing for higher air-to-fuel ratios and thus using less fuel.
VTEC is a technology that was created to improve performance, lower emissions, and increase gas mileage.