VTEC, short for “Variable Valve Timing and Lift Electronic Control,” is a technology that allows engines to optimize performance and efficiency by adjusting valve timing and lift.
The Honda i-VTEC® engine is known for delivering a thrilling driving experience while maintaining impressive fuel efficiency. But have you ever wondered how this advanced technology actually works?
Unlike traditional valve timing systems that rely on a single camshaft, the i-VTEC® system uses two camshafts and an electronic control unit (ECU) to control valve timing and lift precisely.
This allows the engine to switch between different operating modes, depending on the driving conditions, to optimize performance and efficiency.
Let’s take a closer look at the inner workings of the Honda i-VTEC® engine and explore how it provides drivers with a perfect balance of power and fuel efficiency.
The Honda i-VTEC® Engine Explained
Honda’s engineer Ikuo Kajitani came up with the idea for Honda’s original VTEC system. A solution to the problem of getting high output out of small displacement engines while maintaining fuel efficiency was achieved.
As a result of adjusting the internal valve lift and timing, Kajitani could boost performance without adding costly turbochargers or superchargers.
What’s the trick?
The engine computer selects between low and high-performance camshafts using VTEC (Variable Valve Timing & Lift Electronic Control) technology.
Instead of just changing the valve timing as in normal VVT (variable valve timing) systems, separate camshaft profiles allow adjusting the lift and the duration of the valve opening.
Understanding VTEC Engines
Four elements are required to generate horsepower in gasoline-powered engines: air, fuel, compression, and spark. To fully understand the VTEC system, we’ll mainly focus on the air component.
Camshafts are part of the engine and control when and how the valves open and close, determining how much air goes into it.
The rocker arms on this camshaft move the valves open and closed when the camshaft rotates. Those with larger lobes can open their valves more widely than those with smaller ones.
You might have missed the last paragraph if you aren’t familiar with engine internals. Here’s a primer on the parts of an engine, as well as an explanation of camshafts and valves.
- Camshaft & Valves
An engine’s camshaft opens the intake and exhaust channels by turning valves on an engine’s long rod. It usually sits above the cylinder and the piston.
When you rotate the intake channel, fuel and air can enter your engine’s cylinders. In another rotation, your spark plug discharges, allowing the fuel to ignite, and the exhaust channel opens as your intake channel closes, releasing exhaust gasses.
In this process, pistons move up and down in the cylinders. An engine can use one camshaft or two, driven either by a timing chain or a timing belt.
Engines produce power in various ways that vary according to several variables. When more air enters the engine, the combustion process accelerates, but too much air doesn’t necessarily make the engine more powerful.
As the engine grows, the valves open and close so quickly that performance is adversely affected. The process described above works well at low revolutions per minute (rpm), but as the engine speeds up, the valves open and close so quickly that performance is adversely affected.
A Brief History of Honda’s VTEC
As part of Honda’s DOHC (Dual OverHead Camshaft) engines in 1989, the VTEC system was introduced in the Honda Integra XSi and was first available in the United States in 1991 with the Acura NSX.
An incredible 197 horsepower was produced by the 1995 Integra Type R (available only in the Japanese market). There was more horsepower per liter of displacement in the engine than in most supercars at the time.
It evolved into Honda i-VTEC® (intelligent-VTEC) after Honda continued to improve the original VTEC system. A Honda four-cylinder vehicle using i-VTEC® was most likely to be sold in 2002. This technology was first available in 2001.
Honda’s VTC (Variable Timing Control) is combined with the original VTEC® system in i-VTEC®. In addition to introducing two camshaft profiles, Honda also introduced variable valve timing to optimize performance.
However, the VTEC system cannot select between low- and high-RPM profiles, even though it controls valve lift duration. Moreover, the intake cam can advance 25 to 50 degrees, giving you optimal valve timing no matter your RPM range.
How Does It Work?
An original VTEC system replaced a single cam lobe and rocker with a locking multi-part rocker arm and two cam profiles. One was optimized for low-RPM stability and fuel efficiency, while the other was designed to maximize power at higher RPMs.
VTEC balances low-RPM fuel efficiency with a high-RPM performance by combining low-RPM fuel efficiency with low-RPM stability. The seamless transition ensures smooth performance across the entire power range.
The engine computer is responsible for switching between the two cam lobes. A computer switches between the efficient and high-performance cam based on speed, load, and engine RPM.
During high-performance cam operation, a solenoid engages the rocker’s arms. After that, the valves are opened and closed per the high-lift profile, allowing the valves to open further and for a longer period.
Increasing the air and fuel entering the engine creates more torque and horsepower. A valve timing, duration, or lift optimized for low-speed performance differs greatly from one for high RPM performance.
The engine produces poor performance at high RPM settings, while at low RPM settings, it produces a rough idle and poor performance.
Because the camshaft is optimized for maximum power at those higher revolutions, muscle cars have rough idles and barely run at low RPMs but scream down the racetrack at high RPMs.
Compared with super-efficient commuter cars that idle smoothly and may even have “zippy” performance, cars that do not lose power at mid- and high-RPMs quickly lose power.
It was decided that Honda would offer two types of i-VTEC configurations. These were unofficially referred to as performance i-VTEC and economy i-VTEC. VTC is an extra feature of performance i-VTEC engines. These engines work much like conventional VTEC engines.
There are, however, some oddball engines on economy models that use i-VTEC technology. During development, Honda placed little importance on impressive power figures, similar to its emissions-conscious VTEC-E from the mid-1990s.
The most notable difference between their exhaust camshafts and intake camshafts is that their exhaust camshafts lack VTEC, and their intake camshafts feature only two lobes and two rocker arms per cylinder instead of three.
Even though the cylinder heads are 16-valved, economy-i-VTEC engines have only one intake valve per cylinder before VTEC engagement.
There is just a small crack on the remaining intake valve, which prevents unburnt fuel from collecting behind it.
When both valves open and close normally, the process is also known as valve idling. It allows the engine to sip fuel at lower speeds and generate more power at higher speeds.
It is even tuned differently to produce low emissions through VTC. Therefore, a swirl develops within the combustion chambers, and a lean air/fuel mixture results in stunning combustion and fuel efficiency but not much power.
Upon opening the secondary intake valve, the valvetrain operates as expected. Unlike traditional VTEC engines, there is no overall increase in lift or duration. Honda fans everywhere will be disappointed to learn that economy i-VTEC engines will only dominate the 2012 model year.
Does VTEC Really Do Anything?
Is it safe to drive in the city? It depends on how you drive. When driven correctly, Honda cars equipped with VTEC technology tend to be more efficient over a wide rpm range than many comparable cars.
The majority of motorists won’t notice their VTEC kicks in, however. Normally, you rarely reach this rev range under normal driving conditions, especially if you have an automatic transmission.
It is active when the engine is running relatively high up in the rev range. The VTEC makes a noticeable difference if you like twisting roads and shifting your own gears.
How VTEC Is Different
Traditional engines have camshafts with lobes that are exactly the same size and open and close valves.
An engine with Honda’s VTEC has a camshaft with two different lobe sizes: two standard outer lobes and a larger center lobe.
When the engine runs at low rpm, the outer lobes are the only ones controlling the valves.
A sudden burst of speed and better performance can be achieved when the center lobe takes over, and the valves open sooner and closer as the engine speeds up.
Also, because of this change, the engine’s pitch suddenly changes – this is the VTEC kicking in.
It was Honda’s goal to improve its cars with Variable Valve Timing and Lift Electronic Control (VTEC) technology so that they would be faster, more efficient, and more enjoyable to drive.
Fast and Furious movies have featured this technology repeatedly in recent years, making it a widely known meme. There is a great deal of buzz around the phrase “VTEC just kicked in, yo! Many people have heard about it, but few understand how it works. It’s now easier for you to do.