Variable Valve Timing & Lift Electronic Control (VTEC) engines became popular when Honda first introduced the tech in 1989. The name certainly gained hype as cars with VTEC engines offered better fuel economy with better performance.
Normally engines are either designed for better fuel mileage by sacrificing performance or vice versa. However, VTEC brought the best of both by making some innovative changes to the regular 4-stroke combustion engine.
Understanding VTEC Engine
To understand the working of VTEC, we have to refresh a bit about the function of valves and camshaft in the internal combustion engine.
The internal combustion needs air, fuel, pressure and spark plugs (petrol engine) to create combustion. During the four-stroke cycle, as the piston goes up and down, it sucks the air inward and pushes it out through the valve ports in the cylinder head.
When the engine is running at high rpm, these valves open and close constantly. For instance, an engine running at 4000 rpm can cause the valves to open and close at around 2000 times per minute.
The camshaft is responsible for the timely operation of inlet and exhaust valves. The camshaft has cam lobes along the shaft. As the shaft rotates, the cam lobes allow the valves to open and close. The shape of cam lobes determines how much a valve will open and when it will close. This makes the timing of the camshaft an important aspect as it defines the efficiency of the engine.
In earlier days, you could either have a camshaft with smaller lobes for low rpm engine and better fuel efficiency or a shaft with larger lobes for high rpm engine and low fuel efficiency.
High performance vehicles have bigger camshafts so intake valves can open sooner and close later as compared to the smaller camshaft. Such vehicles will not perform well at low speed, which brings us to the VTEC.
VTEC combines the perks of small and large camshaft, to give the best of both.
Working of VTEC
The VTEC uses two separate camshaft profiles to deal with low and high rpm of the engine. Instead of a series of single cam lobe, the VTEC uses two-lobe profiles.
A larger cam lobe is sandwiched in between two smaller cam lobes. Each lobe is connected to a separate rocker arm. As the camshaft rotates, the lobes push the rocker arms to control intake and exhaust valves.
The rocker arm paired with the larger cam lob is left disconnected. Hence, the bigger cam lobe will rotate but will do nothing as only the smaller lobes are connected to move the valves. This configuration is ideal for engines with low rpm increasing stability and fuel efficiency.
When the car hits higher rpm on the engine, the ECU responds by engaging the VTEC. The pressurized oil is released into the centre of rocker arms. This forces the two metal pegs to come out and connects the rocker arm with the larger cam lobe.
In short, the outer rocker arms get locked in with the centre rocker arm. This allows larger lobe to control the valve timings so the intake valve can open further and for longer duration.
Alternatively, when the vehicle slows down to lower rpm, the mechanism unlocks the centre rocker arm to disengage the larger lobe. Hence, reverting back to first configuration with smaller cam lobes controlling the valves.
Advent of i-VTEC
The i-VTEC refers to Honda’s intelligent Variable Valve Timing & Lift Electronic Control, which combines the capability of VTEC and Variable Timing Control. The i-VTEC offers more flexibility in terms of cam profile for low and high rpm ranges.
It allows the ECU to control the lobes on the camshaft and change the cam timings as the engine operates under different rpm ranges. Such a feature allows the engine to operate at optimum capacity with maximum performance at every rpm range.
Exclusiveness of VTEC
The VTEC technology is exclusive to Honda and is patented to retain the rights of the technology. Although other manufacturers cannot use VTEC technology in their engine, they have found other ways to achieve variable valve timing under a different name. For instance, Mitsubishi calls their VVT system, Mitsubishi Innovative Valve Timing Electronic Control System (MIVEC).
FAQs
What is meant by VTEC kick in?
When the engine is running at high rpm VTEC kicks in by engaging the larger cam lobe by locking all three cam rocker arms together. This leads to increased engine performance as more air is allowed to enter the inlet.
At what rpm VTEC engages?
VTEC engages at around 3000 to 5500 rpm to maintain maximum engine performance at high speed.
There is no doubt VTEC technology made a breakthrough in the average combustion engine and propelled Honda in the automotive industry in terms of popularity. To test out the innovative technology, check out some of the used Honda cars for sale in the UAE:
- Used Honda Accord for sale
- Second hand Honda Civic for sale
- Used Honda Pilot for sale
- Second hand Honda CR-V for sale
Stay tuned to the UAE’s leading auto blogs for more information on car parts, market trends and automotive technology.
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