Timing system vvt i. Auto Reviews

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.

VVTI is a variable valve timing system developed by Toyota. If this abbreviation is translated from English, then this system is responsible for the intelligent phase shift. Now the second generation of mechanisms is installed on modern Japanese engines. And for the first time, VVTI began to be installed on cars since 1996. The system consists of a coupling and a special VVTI valve. The latter acts as a sensor.

Toyota VVTI valve device

The element consists of a body. The control solenoid is located in the outer part. He is responsible for the movement of the valve. The device also has sealing rings and a connector for connecting the sensor.

General principle of the system

The main control device in this valve timing system is the VVTI clutch. By default, the engine designers designed the valve opening phases to get good traction at low engine speeds. As the rpm increases, so does the oil pressure, due to which the VVTI valve opens. Toyota Camry and its 2.4 liter engine work on the same principle.

After this valve opens, the camshaft will rotate to a certain position relative to the pulley. The cams on the shaft are specially shaped and the intake valves will open slightly earlier as the element rotates. Accordingly, close later. This should have the best effect on the power and torque of the engine at high speeds.

Detailed job description

The main control mechanism of the system (and this is the clutch) is mounted on the engine camshaft pulley. Its body is connected to the star or the rotor is connected directly to the camshaft. Oil from is supplied from one or both sides to each petal of the rotor on the clutch, thereby causing the camshaft to turn. When the engine is not running, the system automatically sets the maximum delay angles. They correspond to the latest opening and closing of the intake valves. When the engine starts, the oil pressure is not strong enough to open the VVTI valve. To avoid any shocks in the system, the rotor is connected to the clutch housing with a pin, which, with an increase in lubrication pressure, will be squeezed out by the oil itself.

The operation of the system is controlled by a special valve. On a signal from the ECU, an electric magnet using a plunger will begin to move the spool, thereby passing oil in one direction or the other. When the motor is stopped, this spool is moved by a spring to set the maximum delay angle. To rotate the camshaft at a certain angle, high pressure oil is supplied through the spool to one side of the petals on the rotor. At the same time, a special cavity opens to drain. It is located on the other side of the petal. After the ECU understands that the camshaft is rotated to the desired angle, the pulley channels overlap and it will continue to be held in this position.

Typical symptoms of a VVTI system problem

So, the system must change the phases of operation. If there are any problems with it, then the car will not be able to function normally in one or more operating modes. There are several symptoms that can indicate malfunctions.

So, the car does not keep idle at the same level. This indicates that the VVTI valve is not working as it should. Also, the "braking" of the engine will tell about various problems in the system. Often, with problems with this phase change mechanism, it is not possible for the motor to operate at low speeds. Another problem with the valve can be indicated by error P1349. If the idle speed is high on the warmed-up power unit, the car does not drive at all.

Possible causes of valve failure

There are not so many main causes of valve malfunctions. There are two that are particularly common. So, the VVTI valve may fail due to the fact that there are breaks in the coil. In this case, the element will not be able to correctly respond to voltage transfers. Troubleshooting is easily done by checking the resistance measurement of the sensor coil winding.

The second reason why the VVTI (Toyota) valve does not work properly or does not work at all is sticking in the stem. The cause of such jamming may be the banal dirt that has accumulated in the channel over time. It is also possible that the sealing gum inside the valve is deformed. In this case, restoring the mechanism is very simple - just clean the dirt from there. This can be done by soaking or soaking the element in special liquids.

How to clean the valve?

Many malfunctions can be cured by cleaning the sensor. First you need to find the VVTI valve. Where this element is located can be seen in the photo below. It's circled in the picture.

Cleaning can be done with carburetor cleaners. To completely clean the system, remove the filter. This element is located under the valve - it is a plug in which there is a hole for the hexagon. The filter also needs to be cleaned with this liquid. After all the operations, it remains only to assemble everything in the reverse order, and then install it without resting against the valve itself.

How to check the VVTI valve?

Checking if the valve is working is very simple. To do this, a voltage of 12 V is applied to the sensor contacts. It must be remembered that it is impossible to keep the element energized for a long time, since it cannot work in such modes for so long. When voltage is applied, the rod will retract inward. And when the chain breaks, it will come back.

If the stem moves easily, then the valve is fully functional. It only needs to be washed, lubricated and can be operated. If it does not work as it should, then repair or replacement of the VVTI valve will help.

Self-repair valve

First, the generator control bar is dismantled. Then remove the fasteners of the hood latch. This will give access to the alternator axle bolt. Next, unscrew the bolt that holds the valve itself, and remove it. Then remove the filter. If the last element and the valve are dirty, then these parts are cleaned. Repair is a check and lubrication. You can also replace the sealing ring. More serious repairs are not possible. If a part doesn't work, it's easier and cheaper to replace it with a new one.

Self-replacement of the VVTI valve

Often cleaning and lubrication does not provide the desired result, and then the question arises of a complete replacement of the part. In addition, after the replacement, many car owners claim that the car began to work much better and fuel consumption decreased.

First, remove the generator control bar. Then remove the fasteners and gain access to the generator bolt. Open the bolt that holds the desired valve. The old element can be pulled out and thrown away, and a new one is put in place of the old one. Then the bolt is tightened, and the car can be operated.

Conclusion

Modern cars are both good and bad at the same time. They are bad because not every operation related to repair and maintenance can be performed independently. But you can do the replacement of this valve with your own hands, and this is a big plus for the Japanese manufacturer.

Variable valve timing system (common international name Variable Valve Timing, VVT) is designed to regulate the parameters of the gas distribution mechanism, depending on the engine operating modes. The use of this system provides an increase in engine power and torque, fuel efficiency and a reduction in harmful emissions.

The adjustable parameters of the gas distribution mechanism include:

• moment of opening (closing) of valves;
• duration of valve opening;
• valve lift.

Together, these parameters make up the valve timing - the duration of the intake and exhaust strokes, expressed by the angle of rotation of the crankshaft relative to the "dead" points. The valve timing is determined by the shape of the camshaft lobe acting on the valve.

Different engine operating modes require different valve timing. So, at low engine speeds, the valve timing should have a minimum duration (“narrow” phases). At high speeds, on the contrary, the valve timing should be as wide as possible and at the same time ensure the overlap of the intake and exhaust strokes (natural exhaust gas recirculation).

The camshaft cam has a certain shape and cannot simultaneously provide narrow and wide valve timing. In practice, the cam shape is a compromise between high torque at low RPM and high power at high RPM. This contradiction is exactly what the system for changing the valve timing resolves.

Depending on the adjustable parameters of the gas distribution mechanism, the following methods of variable valve timing are distinguished:

• rotation of the camshaft;
• the use of cams with different profiles;
• change in valve lift.

The most common are variable valve timing systems using camshaft rotation:

• VANOS (Double VANOS) from BMW;
• VVT-i(Dual VVT-i), Variable Valve Timing with intelligence from Toyota;
• VVT Volkswage Variable Valve Timing n;
• VTC, Variable Timing Control by Honda;
• CVVT, Continuous Variable Valve Timing from Hyundai, Kia, Volvo, General Motors;
• VCP, Variable Cam Phases by Renault.

The principle of operation of these systems is based on the rotation of the camshaft in the direction of rotation, which achieves an early opening of the valves compared to the initial position.

The design of the variable valve timing system of this type includes a hydraulically controlled clutch and a control system for this clutch.

hydraulic clutch(common name phase shifter) directly rotates the camshaft. The clutch consists of a rotor connected to the camshaft, and a housing, which is the camshaft drive pulley. Between the rotor and the housing there are cavities to which engine oil is supplied through the channels. Filling one or another cavity with oil ensures the rotation of the rotor relative to the housing and, accordingly, the rotation of the camshaft at a certain angle.

For the most part, a hydraulically controlled clutch is installed on the intake camshaft. To expand the control parameters in some designs, the couplings are installed on the intake and exhaust camshafts.

The control system provides automatic control of the operation of the hydraulically controlled clutch. Structurally, it includes input sensors, an electronic control unit and actuators. The control system uses Hall sensors that evaluate the positions of the camshafts, as well as other sensors of the engine management system: crankshaft speed, coolant temperature, air flow meter. The engine control unit receives signals from sensors and generates control actions on the actuator - an electro-hydraulic distributor. The distributor is a solenoid valve and provides oil supply to the hydraulically controlled clutch and removal from it, depending on the engine operating modes.

The variable valve timing system provides for operation, as a rule, in the following modes:

• idling ( minimum crankshaft speed);
• maximum power;
• maximum torque.

Another type of variable valve timing system is based on the use of cams of various shapes, which achieves a stepwise change in the duration of the opening and the height of the valves. Known such systems are:

• VTEC, Variable Valve Timing and Lift Electronic Control from Honda;
• VVTL-i, Variable Valve Timing and Lift with intelligence from Toyota;
• MIVEC, Mitsubishi Innovative Valve timing Electronic Control from Mitsubishi;
• Valvelift System from Audi.

These systems have basically the same design and operation, with the exception of the Valvelift System. For example, one of the most famous VTEC system includes a set of cams of various profiles and a control system.

The camshaft has two small and one large cam. Small cams through the corresponding rocker arms (rockers) are connected to a pair of intake valves. The large cam moves the free rocker.

The control system provides switching from one mode of operation to another by actuating the blocking mechanism. The locking mechanism is hydraulically driven. At low engine speeds (low load), the intake valves operate from small cams, while the valve timing is characterized by a short duration. When the engine speed reaches a certain value, the control system activates the locking mechanism. The rocker arms of the small and large cams are connected with a locking pin into one piece, while the force on the intake valves is transmitted from the large cam.

Another modification of the VTEC system has three control modes, determined by the operation of one small cam (opening one intake valve, low engine speed), two small cams (opening two intake valves, medium speed), and a large cam (high speed).

Honda's modern variable valve timing system is the I-VTEC system, which combines the VTEC and VTC systems. This combination significantly expands the engine control parameters.

From a structural point of view, the most advanced version of the variable valve timing system is based on adjusting the valve lift height. This system allows you to abandon the throttle in most engine operating modes. The pioneer in this area is BMW and its system Valvetronic. A similar principle is used in other systems:

• valvematic from Toyota;
• VEL, Variable Valve Event and Lift System by Nissan;
• MultiAir from Fiat;
• VTI, Variable Valve and Timing Injection from Peugeot.

In the Valvetronic system, changing the valve lift is provided by a complex kinematic scheme in which the traditional cam-rocker-valve connection is supplemented by an eccentric shaft and an intermediate lever. The eccentric shaft receives rotation from the electric motor through a worm gear. The rotation of the eccentric shaft changes the position of the intermediate lever, which, in turn, sets a certain movement of the rocker and the corresponding movement of the valve. The change in valve lift is carried out continuously depending on the engine operating modes.

The Valvetronic system is installed only on the intake valves.

VVTi Toyota what is it and how does it work? VVT-i - this is how the designers of the Toyota auto concern called the valve timing control system, which came up with their own system for improving the efficiency of internal combustion engines.

This does not mean that only Toyota has such mechanisms, but we will consider this principle using its example.

Let's start with decryption.

The abbreviation VVT-i sounds in the original language as Variable Valve Timing intelligent, which translates as an intelligent change in valve timing.

This technology was first introduced to the market by Toyota ten years ago, in 1996. All automakers and brands have similar systems, which speaks of their benefits. They are called, however, all in different ways, confusing ordinary motorists.

What did VVT-i bring to engine building? First of all - an increase in power, uniform throughout the entire rev range. Motors have become more economical and therefore more efficient.

The control of the valve timing or the control of the moment of raising and lowering the valves occurs by turning to the desired angle.

How it is implemented technically, we will consider further.

Vvti toyota what is it or how does VVT-i valve timing work?

The Toyota VVT-i system is what it is and why, we understand. Time to delve into her insides.

The main elements of this engineering masterpiece:

• clutch VVT-i;
• solenoid valve (OCV - Oil Control Valve);
• Control block.

The algorithm of this whole construction is simple. The clutch, which is a pulley with cavities inside and a rotor mounted on the camshaft, is filled with pressurized oil.

There are several cavities, and the VVT-i valve (OCV), acting on commands from the control unit, is responsible for this filling.

Under the pressure of oil, the rotor together with the shaft can turn at a certain angle, and the shaft, in turn, determines when to raise and lower the valves.

In the starting position, the position of the intake camshaft provides maximum traction at low engine speeds.

As the engine speed increases, the system rotates the camshaft so that the valves open earlier and close later - this helps to increase output at high speeds.

As you can see, the VVT-i technology, the principle of operation of which was considered, is quite simple, but, nevertheless, effective.

The development of VVT-i technology: what else did the Japanese come up with?

There are other varieties of this technology. So, for example, Dual VVT-i controls the operation of not only the intake camshaft, but also the exhaust ones.

This made it possible to achieve even higher engine parameters. Further development of the idea was called VVT-iE.

Here, Toyota engineers completely abandoned the hydraulic method of controlling the camshaft position, which had a number of disadvantages, because in order to rotate the shaft, it was necessary that the oil pressure rise to a certain level.

It was possible to eliminate this drawback thanks to electric motors - now they turn the shafts. That's it.

Thank you for your attention, now you yourself can answer the question "VVT-i Toyota what is it and how does it work" to anyone.

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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