The Vvt-i valve is a variable valve timing system for an automotive internal combustion engine manufactured by Toyota.

This article contains answers to such fairly common questions:

• What is a Vvt-i valve?
• vvti device;
• What is the principle of operation of vvti?
• How to properly clean vvti?
• How to repair a valve?
• How is the replacement done?

Vvt-i device

The main mechanism is located in the camshaft pulley. The housing is connected together with a toothed pulley, and the rotor with a camshaft. Lubricating oil is delivered to the valve mechanism from either side of each petal rotor. Thus the valve and camshaft starts to rotate. At that moment, when the car engine is in a muffled state, the maximum angle of detention is set. This means that an angle is determined that corresponds to the most recent product of the opening and closing of the intake valves. Due to the fact that the rotor is connected to the housing by a locking pin immediately after start-up, when the pressure of the oil line is insufficient to effectively control the valve, no shocks can occur in the valve mechanism. After that, the locking pin opens with the help of the pressure that the oil exerts on it.

What is the principle of operation of Vvt-i? Vvt-i provides the ability to smoothly change the gas distribution phases, corresponding to all conditions for the functioning of an automobile engine. This function is ensured by rotating the inlet camshaft relative to the outlet valve shafts, along the angle of rotation of the crankshaft from forty to sixty degrees. As a result, there is a change in the moment of initial opening of the intake valve, as well as the amount of time when the exhaust valves are in the closed position, and the exhaust valves are open. The control of the presented type of valve is due to the signal that comes from the control unit. After a signal is received, an electronic magnet moves the main spool along the plunger, while passing oil in any direction.

At the moment when the car engine is not working, the spool moves with the help of a spring so that the maximum delay angle is located.

To produce a camshaft, oil under a certain pressure is moved to one side of the rotor with the help of a spool. At the same moment, a cavity opens on the other side of the petals to drain the oil. After the control unit determines the location of the camshaft, all the channels of the pulley are closed, thus, it is held in a fixed position. The operation of the mechanism of this valve is carried out by several conditions for the functioning of an automobile engine with different modes.

In total, there are seven modes of operation of an automobile engine, and here is a list of them:

1. Idling movement;
2. Movement at low load;
3. Movement with an average load;
4. Driving with high load and low speed;
5. Traveling with a high load and a high level of rotational speed;
6. Traveling with low coolant temperature;
7. During engine start and stop.

Self cleansing procedure a Vvt-i

Dysfunction is usually accompanied by many signs, so it is most logical to look at these signs first.

So, the main signs of a violation of normal functioning are as follows:

• The car abruptly stalls;
• The vehicle cannot maintain momentum;
• The brake pedal noticeably stiffens;
• Does not pull the brake pedal.

Now we can proceed to consider the process of purification of Vvti. We will carry out the purification of Vvti step by step.

So, the algorithm for cleaning Vvti:

1. Remove the plastic cover of the car engine;
2. We unscrew the bolts and nuts;
3. We remove the iron cover, the main task of which is to fix the generator of the machine;
4. We remove the connector from the Vvti;
5. We unscrew the bolt by ten. Don't be afraid, you won't be able to make a mistake, as there is only one of them.
6. We remove Vvti. Just in no case do not pull on the connector, because it fits snugly enough to it and a sealing ring is placed on it.
7. We clean Vvti with any cleaner that is designed to clean the carburetor;
8. For complete purification of Vvti, remove the filter of the Vvti system. The presented filter is located under the valve and has the form of a plug with a hole for the hexagon, but this item is optional.
9. Cleansing is complete, you just have to assemble everything in reverse order and tighten the belt without resting on Vvti.

Self Repair Vvt-i

Quite often, it becomes necessary to repair the valve, since simply cleaning it is not always effective.

So, first, let's look at the main signs of the need for repairs:

• The car engine does not hold idle;
• Brakes the engine;
• It is impossible to move the car at low speeds;
• No brake booster;
• Poor gear changes.

Let's look at the main causes of valve failure:

• The coil broke. In this case, the valve will not be able to respond correctly to the voltage transfer. This violation can be determined by measuring the resistance of the winding.
• Seizes the stock. The cause of stem sticking can be the accumulation of dirt in the stem bore or deformation of the rubber that is located inside the stem. Dirt can be removed from the channels by soaking or soaking.

Valve repair algorithm:

1. We remove the regulating bar of the car generator;
2. We remove the fasteners of the lock of the hood of the car, thanks to this you can get access to the axial bolt of the generator;
3. We remove the valve. Just in no case do not pull on the connector, because it fits snugly enough to it and a sealing ring is placed on it.
4. We remove the filter of the Vvti system. The presented filter is located under the valve and has the form of a plug with a hole for the hexagon.
5. If the valve and filter are very dirty, then we clean them with a special liquid for cleaning the carburetor;
6. We check the operability of the valve, using a short supply of twelve volts to the contacts. If you are satisfied with how it functions, then you can stop at this stage, if not, then follow these steps.
7. We put marks on the valve in order to prevent mistakes during re-installation;
8. Using a small screwdriver, disassemble the valve from two sides;
9. We take out the stock;

1. We wash and clean the valve;
2. If the valve ring is deformed, then replace it with a new one;
3. Roll up the inside of the valve. This can be done with the help of a cloth, by pressing on the rod, to press the new sealing ring;
4. Change the oil that is in the coil;
5. We replace the ring, which is located on the outside;
6. Roll the outer side of the valve to press the outer ring;
7. The valve repair is completed and you just have to assemble everything in the reverse order.

Vvt-i valve self-replacement procedure

Often, cleaning and repairing the valve does not give much results, and then it becomes necessary to completely replace it. In addition, many motorists claim that after replacing the valve, the vehicle will work much better and fuel costs will drop to about ten liters.

Therefore, the question arises: How should the valve be replaced correctly? We will replace the valve step by step.

So, the valve replacement algorithm:

1. Remove the car alternator control bar;
2. Remove the fasteners of the lock of the hood of the car, thanks to this you will be able to gain access to the axial bolt of the generator;
3. We unscrew the bolt that secures the valve;
4. We take out the old valve;
5. We install a new valve in place of the old one;
6. We twist the bolt securing the valve;
7. The valve replacement is complete and you just have to assemble everything in the reverse order.

Not really

VVT-iW scheme - timing chain drive for both camshafts, phase change mechanism with vane rotors on the intake and exhaust camshaft sprockets, extended intake adjustment range. Used on engines 6AR-FSE, 8AR-FTS, 8NR-FTS, 2GR-FKS...

System VVT-iW(Variable Valve Timing intelligent Wide) allows you to smoothly change the valve timing in accordance with the operating conditions of the engine. This is achieved by turning the intake camshaft relative to the drive sprocket in the range of 75-80 ° (by the angle of rotation of the crankshaft).

Extended, compared to conventional VVT, the range falls mainly on the delay angle. The VVT-i drive is installed on the second camshaft in this scheme.

The VVT-i (Variable Valve Timing intelligent) system allows you to smoothly change the valve timing in accordance with the operating conditions of the engine. This is achieved by turning the exhaust camshaft relative to the drive sprocket in the range of 50-55 ° (by the angle of rotation of the crankshaft).

The joint work of VVT-iW at the inlet and VVT-i at the outlet provides the following effect.
1. Starting mode (EX - advancing, IN - intermediate position). To ensure reliable starting, two independent locks are used to hold the rotor in an intermediate position.
2. Partial load mode (EX - delay, IN - delay). Provides the ability to operate the engine on the Miller / Atkinson cycle, while reducing pumping losses and improving efficiency. More details -.
3. Mode between medium and high load (EX - delay, IN - advance). The so-called mode is provided. internal exhaust gas recirculation and improved exhaust conditions.

The control valve is built into the central bolt of the actuator (sprocket) to the camshaft. At the same time, the control oil channel has a minimum length, providing maximum response speed and operation at low temperatures. The control valve is driven by the piston rod of the VVT-iW solenoid valve.

The design of the valve allows for independent control of two detents, separately for the advance and delay circuits. This allows the rotor to be fixed in the intermediate position of the VVT-iW control.

The VVT-iW solenoid valve is installed in the timing chain cover and connected directly to the intake camshaft timing actuator.

Advance

Delay

Retention

Drive VVT-i

The exhaust camshaft is driven by a VVT-i vane rotor (traditional or new style - with a pilot valve built into the center bolt). When the engine is off, the latch holds the camshaft in the maximum advance position to ensure normal starting.

The auxiliary spring applies a moment in the forward direction to return the rotor and securely engage the detent after the engine is turned off.

The control unit, by means of an e / m valve, controls the oil supply to the advance and delay cavities of the VVT ​​drive, based on the signals from the camshaft position sensors. With the engine off, the spool is moved by a spring in such a way as to provide the maximum advance angle.

Advance. The E/m valve on a signal ECM switches to a forward position and shifts the control valve spool. Engine oil under pressure enters the rotor from the side of the advance cavity, turning it together with the camshaft in the advance direction.

Delay. The E/m valve on a signal ECM switches to a position of a delay and shifts the control valve spool. Pressurized engine oil enters the rotor from the side of the delay cavity, turning it along with the camshaft in the direction of the delay.

Retention. The ECM calculates the required advance angle according to driving conditions, and after setting the target position, switches the control valve to the neutral position until the next change in external conditions.

A split gear that allows you to adjust the valve opening / closing phases was previously considered an accessory only to sports cars. In many modern engines, the variable valve timing system is used regularly and works not only for the benefit of increasing power, but also to reduce fuel consumption and emissions of harmful substances into the environment. Let's consider how Variable Valve Timing (the international name for systems of this type) works, as well as some features of the VVT ​​device on BMW, Toyota, Honda cars.

Fixed phases

Valve timing is usually called the opening and closing moments of the intake and exhaust valves, expressed in degrees of rotation of the crankshaft relative to BDC and TDC. In graphical terms, it is customary to show the period of opening and closing with a diagram.

If we are talking about phases, then the following can be changed:

• the moment when the intake and exhaust valves begin to open;
• duration of stay in the open state;
• lift height (the amount by which the valve is lowered).

The vast majority of engines have fixed valve timing. This means that the parameters described above are determined only by the shape of the camshaft cam. The disadvantage of such a constructive solution is that the shape of the cams calculated by the designers for the operation of the engine will be optimal only in a narrow speed range. Civilian engines are designed in such a way that the valve timing corresponds to the normal operating conditions of the car. After all, if you make an engine that will go very well “from the bottom”, then at speeds above average, the torque, as well as peak power, will be too low. It is this problem that the variable valve timing system solves.

How the VVT ​​works

The essence of the VVT ​​system is to adjust the valve opening phases in real time, focusing on the engine operating mode. Depending on the design features of each of the systems, this is implemented in several ways:

• turning the camshaft relative to the camshaft gear;
• the inclusion in the work at certain speeds of the cams, the shape of which is suitable for power modes;
• change in valve lift.

The most widespread are systems in which phase adjustment is carried out by changing the angular position of the camshaft relative to the gear. Despite the fact that a similar principle is put into operation of different systems, many automakers use individual designations.

• Renault – Variable Cam Phases (VCP).
• BMW - VANOS. Like most automakers, initially only the intake camshaft was equipped with such a system. The system, in which the variable valve timing fluid couplings are installed on the exhaust camshaft, is called Double VANOS.
• Toyota - Variable Valve Timing with intelligence (VVT-i). As in the case of BMW, the presence of a system on the intake and exhaust camshafts is called Dual VVT.
• Honda - Variable Timing Control (VTC).
• Volkswagen in this case acted more conservatively and chose the international name - Variable Valve Timing (VVT).
• Hyundai, Kia, Volvo, GM - Continuous Variable Valve Timing (CVVT).

How phases affect engine performance

At low speeds, the maximum filling of the cylinders will provide a late opening of the exhaust valve and an early closing of the intake. In this case, the valve overlap (the position in which the exhaust and intake valves are open at the same time) is minimal, therefore, the possibility of pushing the exhaust gases remaining in the cylinder back into the intake is eliminated. It is because of the wide-phase ("top") camshafts on forced motors that it is often necessary to set increased idle speeds.

At high speeds, to get the most out of the engine, the phases should be as wide as possible, since the pistons will pump much more air per unit time. In this case, the overlapping of the valves will have a positive effect on the scavenging of the cylinders (output of the remaining exhaust gases) and subsequent filling.

That is why the installation of a system that allows you to adjust the valve timing, and in some systems the valve lift, to the engine operating mode, makes the engine more flexible, more powerful, more economical and at the same time friendlier to the environment.

Device, principle of operation of VVT

The phase shifter is responsible for the angular displacement of the camshaft, which is a fluid coupling, the operation of which is controlled by the engine ECU.

Structurally, the phase shifter consists of a rotor, which is connected to the camshaft, and a housing, the outer part of which is the camshaft gear. Between the housing of the hydraulically controlled clutch and the rotor there are cavities, the filling of which with oil leads to the movement of the rotor, and, consequently, the displacement of the camshaft relative to the gear. In the cavity, oil is supplied through special channels. The adjustment of the amount of oil flowing through the channels is carried out by an electro-hydraulic distributor. The distributor is a conventional solenoid valve that is controlled by the ECU via a PWM signal. It is the PWM signal that makes it possible to smoothly change the valve timing.

The control system, in the form of an engine ECU, uses the signals from the following sensors:

• DPKV (calculated the frequency of rotation of the crankshaft);
• DPRV;
• TPS;
• DMRV;
• DTOZH.

Systems with different cam shapes

Due to the more complex design, the system for changing the valve timing by acting on the rocker arms of the cams of various shapes has become less widespread. As in the case of Variable Valve Timing, automakers use different designations to refer to systems that are similar in principle.

• Honda - Variable Valve Timing and Lift Electronic Control (VTEC). If both VTEC and VVT are used on the engine at the same time, then such a system is abbreviated as i-VTEC.
• BMW - Valvelift System.
• Audi - Valvelift System.
• Toyota - Variable Valve Timing and Lift with intelligence from Toyota (VVTL-i).
• Mitsubishi - Mitsubishi Innovative Valve timing Electronic Control (MIVEC).

Principle of operation

Honda's VTEC system is perhaps one of the most famous, but other systems work in a similar way.

As you can see from the diagram, in the low-speed mode, the force on the valves through the rocker arms is transmitted by the incursion of the two extreme cams. In this case, the middle rocker moves "idle". When switching to high speed mode, oil pressure extends the locking rod (locking mechanism), which turns 3 rocker arms into a single mechanism. The increase in valve travel is achieved due to the fact that the middle rocker arm corresponds to the camshaft cam with the largest profile.

A variation of the VTEC system is a design in which the modes: low, medium and high speeds correspond to different rocker arms and cams. At low speeds, the smaller cam opens only one valve, at medium speeds, the two smaller cams open 2 valves, and at high speeds, the largest cam opens both valves.

The last stage of development

A stepwise change in the duration of the opening and the height of the valves allows not only to change the valve timing, but also to almost completely remove the function of regulating the load on the engine from the throttle valve. This is primarily about the Valvetronic system from BMW. It was BMW specialists who first achieved such results. Now similar developments have: Toyota (Valvematic), Nissan (VVEL), Fiat (MultiAir), Peugeot (VTI).

The throttle valve, opened at a small angle, creates a significant resistance to the movement of air flows. As a result, part of the energy received from the combustion of the air-fuel mixture is spent on overcoming pumping losses, which negatively affects the power and economy of the car.

In the Valvetronic system, the amount of air entering the cylinders is controlled by the degree of lift and the duration of the opening of the valves. This was realized by introducing an eccentric shaft and an intermediate lever into the design. The lever is connected by a worm gear to a servo driven by the ECU. Changing the position of the intermediate lever shifts the action of the rocker in the direction of greater or lesser opening of the valves. In more detail, the principle of operation is shown in the video.

The efficiency of an internal combustion engine often depends on the process of gas exchange, that is, filling the air-fuel mixture and removing exhaust gases. As we already know, the timing (gas distribution mechanism) is engaged in this, if you correctly and “finely” adjust it to certain speeds, you can achieve very good results in efficiency. Engineers have been struggling with this problem for a long time, it can be solved in various ways, for example, by acting on the valves themselves or by turning the camshafts ...

In order for the internal combustion engine valves to always work correctly and not be subject to wear, at first simply “pushers” appeared, then, but this turned out to be not enough, so manufacturers began to introduce so-called “phase shifters” on camshafts.

Why are phase shifters needed at all?

To understand what phase shifters are and why they are needed, read useful information first. The thing is that the engine does not work the same at different speeds. For idle and not high speeds, "narrow phases" are ideal, and for high - "wide".

narrow phases - if the crankshaft rotates "slowly" (idling), then the volume and speed of exhaust gases are also small. It is here that it is ideal to use “narrow” phases, as well as minimal “overlap” (the time of simultaneous opening of the intake and exhaust valves) - the new mixture is not pushed into the exhaust manifold, through the open exhaust valve, but, accordingly, the exhaust gases (almost) do not pass into the intake . It's the perfect combination. If, however, “phasing” is made wider, precisely at low rotations of the crankshaft, then “working out” can mix with incoming new gases, thereby reducing its quality indicators, which will definitely reduce power (the motor will become unstable or even stall).

Wide phases - when the speed increases, the volume and speed of the pumped gases increase accordingly. Here it is already important to blow out the cylinders faster (from mining) and quickly drive the incoming mixture into them, the phases should be “wide”.

Of course, the usual camshaft leads the discoveries, namely its “cams” ​​(kind of eccentrics), it has two ends - one is as if sharp, it stands out, the other is simply made in a semicircle. If the end is sharp, then the maximum opening occurs, if it is rounded (on the other hand) - the maximum closure.

BUT regular camshafts have NO phase adjustment, that is, they cannot expand or make them narrower, yet engineers set average indicators - something between power and efficiency. If you fill up the shafts to one side, then the efficiency or economy of the engine will drop. “Narrow” phases will not allow the internal combustion engine to develop maximum power, but “wide” phases will not work normally at low speeds.

That would be regulated depending on the speed! This was invented - in fact, this is the phase control system, SIMPLY - PHASE SHIFTER.

Principle of operation

Now we will not go deep, our task is to understand how they work. Actually, a conventional camshaft at the end has a timing gear, which in turn is connected to.

The camshaft with a phase shifter at the end has a slightly different, modified design. Here are two "hydro" or electrically controlled clutches, which on the one hand are also engaged with the timing drive, and on the other hand with the shafts. Under the influence of hydraulics or electronics (there are special mechanisms), shifts can occur inside this clutch, so it can turn a little, thereby changing the opening or closing of the valves.

It should be noted that the phase shifter is not always installed on two camshafts at once, it happens that one is on the intake or exhaust, and on the second it’s just a regular gear.

As usual, the process is managed, which collects data from various ones, such as the position of the crankshaft, hall, engine speed, speed, etc.

Now I suggest that you consider the basic designs of such mechanisms (I think this will clear up your mind more).

VVT (Variable Valve Timing), KIA-Hyundai (CVVT), Toyota (VVT-i), Honda (VTC)

One of the first to offer to rotate the crankshaft (relative to the initial position), Volkswagen, with its VVT system (many other manufacturers built their systems on its basis)

What does it include:

Phase shifters (hydraulic), mounted on the intake and exhaust shafts. They are connected to the engine lubrication system (actually, this oil is pumped into them).

If you disassemble the clutch, then inside there is a special sprocket of the outer case, which is fixedly connected to the rotor shaft. The housing and rotor can move relative to each other when pumping oil.

The mechanism is fixed in the head of the block, it has channels for supplying oil to both clutches, flows are controlled by two electro-hydraulic distributors. By the way, they are also fixed on the block head housing.

In addition to these distributors, there are many sensors in the system - crankshaft frequency, engine load, coolant temperature, position of the camshafts and crankshafts. When you need to turn to correct the phases (for example, high or low speeds), the ECU, reading the data, instructs the distributors to supply oil to the couplings, they open and the oil pressure begins to pump up the phase shifters (thus they turn in the right direction).

Idling - rotation occurs in such a way that the “inlet” camshaft provides a later opening and later closing of the valves, and the “exhaust” turns so that the valve closes much earlier before the piston approaches top dead center.

It turns out that the amount of the used mixture is reduced almost to a minimum, and it practically does not interfere with the intake stroke, this favorably affects the operation of the engine at idle, its stability and uniformity.

Medium and high rpm - here the task is to give out maximum power, so the "turning" occurs in such a way as to delay the opening of the exhaust valves. Thus, the gas pressure remains on the stroke stroke. Inlet, in turn, open after reaching the top dead center (TDC) of the piston, and close after BDC. Thus, we kind of get the dynamic effect of “recharging” the engine cylinders, which brings with it an increase in power.

Max Torque - as it becomes clear, we need to fill the cylinders as much as possible. To do this, you need to open the intake valves much earlier and, accordingly, close the intake valves much later, save the mixture inside and prevent it from escaping back into the intake manifold. "Graduation", in turn, are closed with some lead to TDC in order to leave a slight pressure in the cylinder. I think this is understandable.

Thus, many similar systems are currently operating, of which the most common are Renault (VCP), BMW (VANOS / Double VANOS), KIA-Hyundai (CVVT), Toyota (VVT-i), Honda (VTC).

BUT these are not ideal either, they can only shift the phases in one direction or another, but they cannot really "narrow" or "expand" them. Therefore, more advanced systems are now beginning to appear.

Honda (VTEC), Toyota (VVTL-i), Mitsubishi (MIVEC), Kia (CVVL)

To further control the valve lift, even more advanced systems were created, but the ancestor was HONDA, with its own motor VTEC(Variable Valve Timing and Lift Electronic Control). The bottom line is that in addition to changing the phases, this system can raise the valves more, thereby improving the filling of the cylinders or the removal of exhaust gases. HONDA is now using the third generation of such motors, which have absorbed both VTC (phase shifters) and VTEC (valve lift) systems at once, and now it is called - DOHC i- VTEC .

The system is even more complex, it has advanced camshafts that have combined cams. Two conventional ones on the edges that press the rocker arms in normal mode and a middle, more extended cam (high profile) that turns on and presses the valves after, say, 5500 rpm. This design is available for each pair of valves and rocker arms.

How does it work VTEC? Up to about 5500 rpm, the motor operates normally, using only the VTC system (that is, it turns the phase shifters). The middle cam, as it were, is not closed with the other two at the edges, it simply rotates into an empty one. And when high speeds are reached, the ECU gives the order to turn on the VTEC system, oil begins to be pumped in and a special pin is pushed forward, this allows you to close all three “cams” ​​at once, the highest profile starts to work - now it is he who presses a pair of valves for which it is designed Group. Thus, the valve drops much more, which allows you to additionally fill the cylinders with a new working mixture and divert a larger amount of "working out".

It is worth noting that VTEC is on both the intake and exhaust shafts, this gives a real advantage and an increase in power at high speeds. An increase of about 5-7% is a very good indicator.

It is worth noting, although HONDA was the first, now similar systems are used on many cars, such as Toyota (VVTL-i), Mitsubishi (MIVEC), Kia (CVVL). Sometimes, as for example in the Kia G4NA engines, a valve lift is used on only one camshaft (here only on the intake).

BUT this design also has its drawbacks, and the most important is the stepwise inclusion in the work, that is, eat up to 5000 - 5500 and then you feel (the fifth point) the inclusion, sometimes as a push, that is, there is no smoothness, but I would like to!

Soft start or Fiat (MultiAir), BMW (Valvetronic), Nissan (VVEL), Toyota (Valvematic)

If you want smoothness, please, and here the first company in development was (drum roll) - FIAT. Who would have thought they were the first to create the MultiAir system, it is even more complex, but more accurate.

“Smooth operation” is applied here on the intake valves, and there is no camshaft here at all. It was preserved only on the exhaust part, but it also has an effect on the intake (probably confused, but I will try to explain).

Principle of operation. As I said, there is one shaft here, and it controls both the intake and exhaust valves. HOWEVER, if it affects the “exhaust” mechanically (that is, it is trite through the cams), then the inlet effect is transmitted through a special electro-hydraulic system. On the shaft (for intake) there is something like “cams” ​​that do not press the valves themselves, but the pistons, and they transmit orders through the solenoid valve to the working hydraulic cylinders to open or close. Thus, it is possible to achieve the desired opening in a certain period of time and revolutions. At low speeds, narrow phases, at high - wide, and the valve extends to the desired height, because here everything is controlled by hydraulics or electrical signals.

This allows you to make a smooth start depending on the engine speed. Now many manufacturers also have such developments, such as BMW (Valvetronic), Nissan (VVEL), Toyota (Valvematic). But these systems are not perfect to the end, what is wrong again? Actually, here again there is a timing drive (which takes about 5% of the power), there is a camshaft and a throttle valve, this again takes a lot of energy, respectively, steals efficiency, it would be nice to refuse them.

20.08.2013

This system provides the optimum intake torque in each cylinder for given specific engine operating conditions. VVT-i virtually eliminates the traditional trade-off between big low-end torque and high-end power. VVT-i also provides greater fuel economy and reduces emissions of harmful combustion products so effectively that there is no need for an exhaust gas recirculation system.

VVT-i engines are installed on all modern Toyota vehicles. Similar systems are being developed and used by a number of other manufacturers (for example, the VTEC system from Honda Motors). Toyota's VVT-i system replaces the previous VVT (Hydraulically Actuated 2-Stage Control) system used since 1991 on 20-valve 4A-GE engines. VVT-i has been in use since 1996 and controls the opening and closing of the intake valves by changing the gear between the camshaft drive (belt, gear or chain) and the camshaft itself. The camshaft position is controlled hydraulically (pressurized engine oil).

In 1998, Dual (“double”) VVT-i appeared, controlling both intake and exhaust valves (first installed on the 3S-GE engine on the RS200 Altezza). Also, dual VVT-i is used on new Toyota V-engines, such as the 3.5-liter V6 2GR-FE. Such an engine is installed on Avalon, RAV4 and Camry in Europe and America, on Aurion in Australia and on various models in Japan, including Estima. Dual VVT-i will be used in future Toyota engines, including a new 4-cylinder engine for the next generation Corolla. In addition, dual VVT-i is used in the D-4S 2GR-FSE engine on the Lexus GS450h.

Due to the change in the moment of opening the valves, the start and stop of the engine are practically imperceptible, since the compression is minimal, and the catalyst heats up very quickly to the operating temperature, which dramatically reduces harmful emissions into the atmosphere. VVTL-i (stands for Variable Valve Timing and Lift with intelligence) Based on VVT-i, the VVTL-i system uses a camshaft that also controls how much each valve opens when the engine is running at high speeds. This allows not only higher engine speeds and more power, but also the optimal opening moment of each valve, which leads to fuel savings.

The system was developed in cooperation with Yamaha. VVTL-i engines are found in modern Toyota sports cars such as the Celica 190 (GTS). In 1998, Toyota began offering the new VVTL-i technology for the 2ZZ-GE twin camshaft 16 valve engine (one camshaft controls the intake and the other exhaust valves). Each camshaft has two lobes per cylinder, one for low RPM and one for high RPM (large opening). Each cylinder has two intake and two exhaust valves, and each pair of valves is driven by a single rocker arm, which is acted upon by a camshaft cam. Each lever has a spring-loaded sliding follower (the spring allows the follower to slide freely over the "high speed" cam without affecting the valves). When the engine speed is below 6000 rpm, the rocker arm is actuated by a "low speed cam" through a conventional roller follower (see illustration). When the frequency exceeds 6000 rpm, the engine control computer opens the valve, and oil pressure moves the pin under each sliding pushrod. The pin supports the sliding pusher, as a result of which it no longer moves freely on its spring, but begins to transfer the impact from the "high-speed" cam to the rocking lever, and the valves open more and for a longer time.