The creation of TokyoTOYOTA MOTOR CORPORATION’s new “Variable Valve Timing-intelligent” (VVT-i) technology, which improves performance and fuel efficiency, was unveiled today.
Modern engine development must focus on both improved fuel efficiency and improved vehicle performance. The societal needs of protecting the environment and natural resources must also be met by modern engines.
Toyota added the WT mechanism to their 4A-GE sports engines in 1991 in an effort to boost engine production and torque. Depending on the state of the engine, WT permits the intake valve to open and close in two phases.
An enhanced version of the WT mechanism is called VVT-i. In order to deliver the best valve timing dependent on driving conditions, VVT-i continually modifies the open/close time of the intake valve. The benefits of VVT-i include improved fuel efficiency, higher torque and output, and decreased nitrogen oxide (NOx) and hydrocarbon emissions.
The VVT-straightforward i’s architecture makes it incredibly dependable and simple to adapt for already-existing engine designs. The new technology is anticipated to have numerous uses in the future.
A new model that will be released within the year will be the first to integrate VVT-i engines. According to tests, VVT-i improves low- and medium-range torque by roughly 10% while also increasing fuel economy by about 6%.
In This Article...
Design
The electronic control unit (ECU), which determines the ideal intake valve timing based on engine operating conditions, the oil control valve (OCV), which regulates hydraulic pressure in response to the ECU’s commands, and the WT pulley, which continuously modifies the intake valve timing using hydraulic pressure, make up VVT-i. The WT pulley uses the standard engine oil pump, thus it doesn’t require a separate pump to work.
A piston with a helical spline is moved hydraulically in the direction of the pulley during VVT operation.
The helical spline with a significant spiral angle of (30) is now attainable thanks to new manufacturing technologies developed by Toyota. This results in an extremely quick response and a wide changeable angle (up to 60 crankshaft angle) with a short stroke in the camshaft axis direction.
Another benefit of the OCV is that it continuously regulates the hydraulic pressure used to advance and retard the timing of the valves.
Performance Features
Better fuel efficiency and lower NOx and hydrocarbon emissions
By continuously and broadly controlling the intake valve timing based on the engine load and speed, valve overlap (the timing when both the intake and exhaust valves are open) is produced, which improves fuel efficiency and lowers NOx and hydrocarbon emissions.
When the accelerator pedal is not fully depressed, the throttle valve in a typical gasoline engine regulates the air intake (partial-load driving). As a result, the cylinder creates vacuum pressure, increasing the stress on the piston (pumping loss).
On the other hand, an engine with VVT-i increases valve overlap, advances the timing for opening the intake valve during partial-load driving, and draws some exhaust gas back into the cylinder. This has three effects: reducing the negative pressure inside the cylinder to decrease intake loss and improve fuel efficiency; lowering the combustion temperature to reduce NOx; and returning unburned gas to the combustion chamber to be reburned to lower the amount of hydrocarbons.
When the engine is idle, the valves do not overlap to maintain combustion, and the idling speed is reduced to increase fuel efficiency.
increased output and torque
Based on engine speed, the intake valve timing is given optimal (continuous and broad) control during high-load driving conditions that call for high torque and output. By increasing intake air, the intake inertia effect is completely utilized to boost torque and output.
The timing of the intake valve closing must be chosen in proportion to the intake inertia effect and the intake air return brought on by a rising piston in order to enhance the amount of intake air. Timing adjustments are made in accordance with engine speed.
By anticipatorily managing intake valve closure in the low- and medium-speed ranges, the VVT-i engine boosts low- and medium-speed torque. The timing for shutting the intake valve is delayed to maximize output as engine speed increases.
What does Toyota’s VVT stand for?
Techniquest Glyndr’s ZR engine with intelligent variable valve timing, shown in a cutaway view.
Toyota created the variable valve timing technology known as VVT-i, or variable valve timing with intelligence, for use in automobiles. The Toyota VVT-i system takes the place of the Toyota VVT, which was available on the 4A-GE engine’s 5-valve per cylinder starting in 1991. The VVT system is a two-stage cam phasing mechanism that is hydraulically regulated.
VVT-i, which debuted on the 2JZ-GE engine in 1995 for the JZS155 Toyota Crown and Crown Majesta, modifies the interaction between the intake camshaft and camshaft drive (a belt or chain). An actuator is subjected to engine oil pressure in order to change the camshaft position. Engine efficiency is increased by adjusting the gap between the opening of the intake valve and the shutting of the exhaust valve. [1] Subsequent variations of the system include included VVTL-i, Dual VVT-i, VVT-iE, VVT-iW, and Valvematic.
Cam-Phasing VVT
as a 0 or a 30. An improved system has continuous variable shifting, for example, any arbitrarily chosen number between 0 and 30, depending on rpm.
Advantage:
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vehicle manufacturers like:
What RPM does VVT operate at?
First, have a look at this definition of “Engine valve-timing.” Just like humans, an automobile engine actually “breathes” (inhales/exhales) through its valves. Human labor is a major factor in determining how quickly people breathe. For instance, the person(s) will breathe more slowly when they are resting or sleeping than when they are moving around or jogging. Additionally, people need to open their mouths to breathe more air while performing sports like swimming or lifting weights.
This is because the need for air intake increases when the human body is put through severe work. As a result, breathing becomes quicker, and the mouth may expand wider to take in more air. Similar to this, when an engine is running quickly, its inlet valves must open earlier, faster, and for a longer time. This is due to the fact that it needs to suck in more air-fuel combination (charge) for burning in order to produce more power.
The length of time that the valves were open in previous conventional engines was optimized only for one engine speed. However, when engine speed rises, the amount of time needed to completely fill the cylinders decreases noticeably. As a result, the engine would receive less charge (air-fuel mixture), which would result in power loss, especially at high engine speeds.
The engineers created the VVT, or “Variable Valve Timing” technology, to address this shortcoming. For a variety of engine speeds, the VVT modifies the timing of valve opening and closing. The Inlet valves open more earlier when the engine is moving quickly, allowing more air-fuel mixture, or “charge,” to reach the cylinders. This contributes to an increase in the engine’s breathing, which greatly enhances its “volumetric efficiency.”
How VVT Works?
The timing of the valves opening and shutting for various engine speeds is further optimized by the variable valve timing system. Two-step variation is used in the first-generation VVT design to optimize the engine for two distinct engine speeds. With this design, two sets of timings are possible: one for the “part-load” situation, which is defined as up to 3500 rpm, and another for the “full-load” condition, which is defined as above 3500 rpm. Additionally, VVT frequently enhances performance and lowers emissions. Additionally, VVT offers the best of both worlds. As a result, it offers maximum power at high rpm and smooth idling at low rpm.
Additionally, the current generation VVT design employs the CVVT system, often known as continuously variable valve timing. Additionally, the engine ECU digitally controls the CVVT, which continually (or eternally) alters the valve timing. For all engine speeds and conditions, it also optimizes valve timing. Although there are various ways to produce the variation, solenoid valves and a “variable-timing camshaft” are primarily used to do so.
In addition, the flexible hydraulic connection between the camshaft and its sprocket is used by the CVVT. It is controlled by the engine’s ECU and an oil control valve that is solenoid-operated. It is powered by the engine’s oil pressure. Additionally, it advances the timing of the Inlet valves opening and advances the camshaft. Some more sophisticated designs employ “Dual” systems, or “Dual VVTi” engines, one of each for independently adjusting the inlet and exhaust valve timings.
What is VVL / VVEL / VVTL?
VVEL stands for “Variable Valve Event and Lift,” whereas VVL stands for “Variable Valve Lift.” Variable Valve Timing and Lift, or VVTL, is a cutting-edge supporting system that modifies the valves’ “lift.” In order to boost performance, the “VVL” system is now more frequently utilized in conjunction with “Variable Valve Timing” (VVT) systems.
According on the engine’s speed, this design also changes the lift (or travel) of the inlet valves and the timing of the valves. As a result, it makes it easier for inlet valves to “low-lift” when moving at idle or low speeds and “high-lift” when moving quickly. Additionally, it offers accurate control over the valve opening and closing. Additionally, manufacturers have created a wide range of additional assistance technologies in order to comply with tougher emissions regulations. These include cam-less valve systems, electro-mechanical or electro-hydraulic valve lifters, etc.
How can I tell whether my VVT is functioning?
The engine will also misfire or appear to stumble if your VVT switch is malfunctioning while your car is carrying extra weight, going up hills, or when you press hard on the accelerator to accelerate quickly. This is frequently brought on by a switch’s electrical malfunction rather than always by the switch itself. It’s likely that the variable valve timing switch won’t need to be replaced if you identify this issue and call a nearby ASE-certified repair to evaluate the situation. However, a correct diagnosis is required to confirm that it is an external issue. The likelihood of future engine damage will rise if you ignore the issue.
Regardless of the exact cause, you should always be proactive and get in touch with a qualified mechanic as soon as you observe any of the aforementioned warning signs or symptoms. The possibility that a problem can be fixed without resulting in further harm to other engine components greatly improves if you identify it as soon as the symptoms appear. As soon as you see any of these symptoms, call a local YourMechanic experienced mechanic.
Toyota VVT-i engines: are they dependable?
Everyone is aware that Toyota manufactures indestructible engines, but like the majority of man-made objects, there are production problems and prospective weaknesses to watch out for. This article will go over the Toyota 4.0 V6’s dependability in detail and the highest mpg you can get out of the v6 monster.
The 2009 and later vehicles’ Dual VVT-i 4.0 V6 engine is quiet, dependable, and smooth, with an engine life that easily exceeds 200,000 miles (320,000 km).
It goes without saying that the secret to an engine’s dependability is routine maintenance and the use of premium oils and lubricants. Undoubtedly, certain engines are more likely than others to experience mechanical and dependability problems.
So how does the 4.0 v6 fare in terms of durability and dependability? What are some of the potential problems you can anticipate and how effective are these engines really?
How can a malfunctioning VVT solenoid be identified?
The Check Engine Light turning on, dirty engine oil, a rough idle, and poor fuel economy are typical symptoms of a bad VVT solenoid.
Is VVT-i preferable to non-VVT-i?
The vvti’s main advantages thus far are that it produces more torque at a lower rpm than the non-vvti, that it is a newer engine with less wear, and that it already has a single turbo.
How reliable are Toyota dual VVT-i engines?
Variable Valve Timing with Intelligence is referred to as VVT-i. Toyota created the technology to automatically and constantly change the intake valve timing to enhance engine performance. The capacity of the system to recognize driving circumstances, such as acceleration or travelling up or down hills, is referred to as the “intelligent element of VVT-i.
Dual VVT-i technology from Toyota improves system performance and helps to further reduce emissions by adjusting both the intake and exhaust valves.
More power, better responsiveness, better mileage, and lower pollutants are the practical results for the driver. Another example of how advancements in engine technology are making cars stronger, cleaner, and more effective is VVT-i.