AVTOVAZ engines will receive a new piston engine, which will allow to avoid bending of the valves when the timing belt breaks.
As you know, one of the disadvantages of modern engines is the bending of the valves when the timing belt breaks. It is quite difficult to predict the resource of the belt, since it can break off not only due to wear, but also when the pump or tension roller is jammed.
When a timing belt breaks, a modern engine usually bends the valves on the pistons. This leads to costly repairs.
AVTOVAZ decided to eliminate this problem, CARscope.ru reports. The plant's supplier, Federal Mogul, has mastered the production of pistons with special notches.
Thanks to this shape, both the pistons and the valves will remain intact, even if the timing belt breaks.
The new piston group is intended for a wide range of engines. This is an 8-valve VAZ-11186 with a capacity of 87 liters. sec., as well as 16-valve engines VAZ-21126 (98 hp) and VAZ-21127 (106 hp), which are installed on the Kalina and Grant family of cars.
The 106-horsepower VAZ-21129 engine, intended for the Vesta and XRAY models, is also soon to receive a version with new pistons. But the new VAZ-21179 unit with a volume of 1.8 liters and a capacity of 122 liters. With. until a new piston is received.
Often in the conversations of motorists, phrases flashed: “I got to be repaired, the belt broke, the valve was bent”. Of course, in such cases we are talking about the timing belt. In order to understand the causes of the "catastrophe", let us consider in general terms the interaction of the connecting rod-piston group and the gas distribution mechanism.
This interaction is strictly coordinated, otherwise the normal operation of the engine will not be ensured.
The principle of operation of the valve-piston system
Let's take a compression cycle as an example. When the piston, compressing the combustible mixture, approaches the top dead center, it almost comes close to the combustion chamber (on diesel engines - to the surface of the head). If at this moment any of the valves is not closed, then the loss of compression will be the lesser evil. Most likely, the valve, the rod of which is rigidly held by the rocker arm (or the cam of the camshaft) from above, will take the piston strike.
The valve bends in the event of a collision of the valve with the piston
In very rare cases, the piston crown has recesses in the piston crown to avoid collisions. From the above, I hope, it is clear why the valve bends when the timing belt breaks: the camshaft stops rotating, some of the valves remain in the open position, being a “convenient target” for pistons moving by inertia.
The coordination of the timing with the crank mechanism is ensured by the precise installation of gears or sprockets. To do this, alignment marks are made on them and at certain points of the engine.
By the type of torque transmission, the drive of the gas distribution mechanism can be:
- Belt
- Chain
- Gear
Consider their common malfunctions, which can lead to bending of the valves.
Timing drive device
Consequences of a broken timing belt
Some curious motorists are interested in the question: is it possible to bend the valve with a starter? The answer is easy! Just do not set the sprockets or gears "by the marks" - and the key is ready to start! If the engine starts, you will immediately learn to recognize the symptoms of kinked valves. Although, if you do not "miss" much, then everything can be fixed by assembling the timing drive according to the rules.
If only one valve is bent, the engine will run unevenly. Even if it's a V-shaped "six" - hear it.
If, after the restoration of the camshaft drive, the engine runs smoothly and develops the same power, then you are in luck and the manufacturer has prudently supplied pistons with sufficient indentations in the bottoms. But, unfortunately, this is not always possible. First of all, when designing a motor, the designer achieves a combination of many seemingly contradictory qualities of his "brainchild". Let's say such as economy and power. This can to some extent serve as an excuse for the fact that on 16-valve motors, the valve often bends when the timing belt breaks.
Such problems are especially acute for the creators of diesel engines, in which the compression and the necessary swirling of the fuel mixture set the power characteristics. Therefore, the combustion chamber is made in the piston crown and often has a whimsical shape.
On diesel engines, the valve bends more often than on gasoline
However, behind this is the accurate calculation and simulation of vortex flows on a computer. Such chambers are called undivided and making recesses for the valves is impractical from the point of view of high-quality atomization and the most efficient combustion of the fuel mixture. The piston comes very close to the block head. Therefore, it is not yet known for certain whether there are diesel engines that “do not bend the valve”. Although, perhaps, the human genius coped with this disaster.
Repair
Curved auto engine valves
Never try to repair bent valves in any way!
Replacement, and only replacement!
If you straighten the valve "by eye", then you risk making yourself more trouble. The hand-rebuilt valve is unlikely to be aligned with the guide bushing and will press firmly against the seat. And if you want to "slightly" trim the rod, then it will work like a pump, pumping oil into the combustion chamber - no cap will hold it.
It would be prudent to troubleshoot other parts as carefully as possible. After all, a blow can damage the guide bushings, valve seats. There are cases when the connecting rods were bent. Breakage of rocker arms is also not uncommon.
Models of VAZ engines, the valves of which are not “afraid” of breaking the timing belt:
VAZ 2111 1.5l; VAZ 21083 1.5L; VAZ 11183 1.6L (8 valve); VAZ 2114 1.5l and 1.6l (both 8 valves)
It is known that the old 8-valve "Opel" engines (such as those on the DAEWOO Nexia and Chevrolet Lanos) also calmly endure this trouble.
As a rule, if a person in his favorite car bent at least one valve, even once, such a person already begins to understand that even “glands” do not have iron patience and will try to become a good master of their “horse”.
In conclusion, it is not superfluous to add - watch your car, do not hesitate if there is a reason to “look under the hood”.
Continuous improvement of the internal combustion engine in order to increase and improve fuel efficiency forced engineers to seriously redesign the design of modern diesel and gasoline engines. The changes also affected the device of the piston group and the combustion chamber. These modifications were made for the most efficient filling of the cylinders and their high-quality ventilation, that is, to obtain improved gas exchange.
If in the early stages of development the most common was the engine with two valves per cylinder (1 inlet and 1 exhaust valve), today there is an increase in the number of valves per cylinder. Such changes are well illustrated by the most common version of the automobile with four cylinders. Previously, such motors were often 8-valve, with one. Today, such a unit is often a 16-valve version with two camshafts (for intake and exhaust valves), can be equipped with a variable valve timing system, etc.
Read in this article
Broken timing belt / chain: main causes
If we compare modern motors with their predecessors, today motors have more power and less resource. As for the problem of bending the valves, it is precisely to achieve greater recoil from the motor that the distance from to is minimal. Even a slightly open valve bends during the lift of the piston at TDC. It turns out that various technical innovations in engine building did not in any way affect the well-known problem that is inherent in the vast majority of engines, regardless of the type of engine and manufacturer. We are talking about the bend of the valves when the drive belt breaks or.
An important rule during the operation of the car is to monitor the condition of the timing belt and its timely replacement. The belt must be free of delamination, cracks or other defects. Also, it is not allowed to get various technical liquids on its surface. The appearance of a squeak, squeak and other extraneous sounds will require the owner to check the tension and condition, as well as the tension and other rollers.
To answer the question when you need to change the timing belt, you need to study the operating instructions for a particular car. Often, on new cars, the belt changes after 60 thousand kilometers traveled or after 2-3 years (whichever comes first). A planned replacement with an original belt involves the next replacement every 50 thousand km. It is advisable to choose non-original belts with care and change every 40 thousand km.
Now a few words about the chain drive. The timing chain requires less attention, since the replacement of the chain is, on average, necessary once every 150-200 thousand km. and more. In this case, it is necessary to monitor the chain tension, the condition of the tensioner and the chain damper. Increased noise during engine operation, the appearance of a metallic clang and other signs will indicate the need for an immediate check of these elements.
So, back to the less reliable belt in comparison with the chain. The timing belt most often breaks for the following reasons:
- belt wear as a result of prolonged use or the use of a poor quality product;
- jamming (water pump);
- wedging of the crankshaft, camshaft;
- malfunction of the tension roller, jamming of the timing rollers;
- destruction of the timing belt as a result of engine oil getting on its surface;
- mechanical damage after contact with sharp edges, camshaft gears;
Why do the valves bend when a belt or timing chain breaks
Despite the improvements, the general traditional principle of operation of the timing and valve train of the engine remains unchanged. As you know, raising the piston at TDC (top dead center) means that at the specified moment the valves are also closed. This is necessary to create pressure and seal the combustion chamber.
If the timing belt breaks, then the valves simply do not have time to close, which means they collide with the piston rising up. When the timing belt breaks, the camshafts stop immediately. This immediate stop occurs for two reasons:
- since the driving force from the belt or chain disappears;
- the camshaft cams themselves are retarded by return springs;
As for the crankshaft, this element continues to rotate by inertia. The inertial rotation of the shaft does not depend on what gear and at what speed the car was moving, at what speed the engine was running, etc. turns the crankshaft anyway. In other words, if the timing belt is cut off, then the gas distribution mechanism stops immediately and the valves remain open, while the crankshaft continues to rotate and the moving pistons hit the open valves at this time.
The result of a broken belt is that the piston meets the valves, after which the valves are immediately bent. The valve stem is often bent, although sometimes various deformations of the valve disc are also possible. Less commonly, damage to the piston itself can be found, which is also a consequence of a belt break and bending of the valves.
Engineers and automakers are familiar with this problem. To prevent the consequences of breaking the timing belt / chain in some old ICEs, special grooves for the valve were made on the piston. These grooves actually provided the necessary free space, which allowed the open valves not to collide with the upward moving piston. In such motors, after a break in the drive, the valve did not bend.
Modern engines also have distinctive piston notches. It should be noted that these grooves avoid the risk of damaging the valve while the engine is running. If the timing belt breaks on such motors, these grooves do not save from bending the valves, that is, the valve still bends even if there are special grooves on the piston.
On which engines the valve bends: how to find out
Due to the severity of this problem and the high cost of subsequent repairs, many motorists are concerned about the question of how to find out if the valve motor is bending or not bending when the timing belt breaks. To more accurately find out and determine whether the valves bend on a particular engine, you can use the following recommendations:
- Study in detail the technical documentation for the engine from the manufacturer. We add that a visual inspection, as well as various data from the tables, still do not give 100% confidence that when the drive belt breaks, the valve does not bend. It is also not recommended to blindly trust the statements on specialized auto forums or rely on information from other more or less authoritative sources. In other words, the validity of any data must be questioned and rechecked.
- Another method is the so-called "physical" check, which allows you to find out yourself if the valves are bent. This method allows you to determine the likelihood of valve bending, that is, to confirm or deny the possibility of contact between the valve and the piston.
In order to find out whether the valve is bending or not bending, you will need to remove the timing belt. Further, the piston in the first cylinder is set to the TDC position, after which the camshaft of the gas distribution mechanism is rotated 720 degrees. If no stop is observed in the process of cranking the camshaft, then it is necessary to make a similar check by alternately raising the pistons in all other ICE cylinders to TDC. If the camshaft does not rest anywhere, then there is a high probability that the valve on this engine will not bend when the belt breaks.
As for the various technical information, which is given in the tables, as well as referring to the experience of auto mechanics and ordinary drivers, the summary data allows us to note:
- often the valve does not bend on simple 8-valve motors;
- usually valves bend on 16-valve and 20-valve engines;
- valve oppression on almost all diesel engines;
- bending of the valves occurs on most engines in the event of a break in the timing chain, that is, on engines with a timing chain drive;
- valves usually bend on engines of small cars with a displacement of 1.1 to 1.4 liters;
Read also
The machine will not start after replacing the timing belt, timing chain or other work on the timing mechanism drive. Main reasons, recommendations.
Every time before buying a car, we think about its engine size, how many "horses" under the hood, what fuel consumption, we compare the car by color, interior trim, and various elements of the exterior. Of course, these questions are important, but no less important is such a parameter as the drive of the gas distribution mechanism, in short, the timing belt.
Reference!
The timing belt is an engine element that acts as a link between the crankshaft and camshaft on any modern car.
Renault Logan engine options
Consider this option that you are going to purchase, the popular Renault Logan people's car. The designers of the Renault concern equipped the cars (except for the top-end configuration) with two types of engines that have passed all kinds of technical tests and have the indices K7J, K7M, which speaks of 1.4 and 1.6 liter 8V engines (valves), respectively. A car of the "LUX" class has a 1.6-liter engine with a 16-valve "head" with the K4M index. In each of them, a belt protrudes in the form of a timing mechanism drive. And about which engine to choose in the material:
Now we will consider each engine separately and figure out in which of them, when the timing belt breaks, the valves will bend.
K7J - 1.4-liter 8-valve engine (valve bends)
The most popular engine among the domestic consumer of the valve is oppression
The four-stroke four-cylinder gasoline engine K7J, evolved in our time straight from the 80s of the XX century. Due to the fact that the engine is a continuation of the line of engines of the previous generation, it has a distinct feature in the form of an outdated design with increased fuel consumption. However, this does not prevent it from remaining one of the most maintainable engines in the lineup.
This engine does not have hydraulic lifters, so every 15-25 thousand kilometers it needs a valve adjustment procedure. And periodically there are oil leaks at the crankshaft oil seal.
Bent 3 valves out of 4
Some "loganovodov" this engine prefer its more powerful version K7M.
K7M - 1.6-liter 8-valve engine (valve bends)
Less popular 1.6-liter 8-valve engine - K7M
The K7M engine from Renault is structurally no different from its predecessor K7J. , the same liquid cooling and combined lubrication system. The same problem with oil leakage and lack of hydraulic lifters remained - we adjust the valves.
Bent valve
However, if you look at the technical characteristics, then this engine has a 10.5 mm increased piston stroke (due to the fact that the block height is changed), as well as the largest engine displacement and flywheel.
Nevertheless, all of the above advantages did not help in any way to save the engine valves, if the timing belt breaks, they are oppressed.
K4M - 1.6-liter 16-valve engine (valve bends)
The valve on the K4M engine is bent
A distinctive feature of this "top" engine from the previous ones is two lightweight camshafts in the cylinder head and a new piston system. From this, the power in comparison with the K7M has increased by 20 hp, while the economy and stability in operation have increased. On the K4M engine, there is no problem with adjusting the valves after a certain mileage interval, since the aforementioned hydraulic lifters are already present there.
The timing drive is still carried out using a belt and, in the same way as on previous engines, when it breaks, it bends the valve.
Causes!
The timing belt can break for various reasons.
From the foregoing, we realized that on all types of Renault Logan car engines, when the timing belt breaks, the valves are bent. And below we will describe the reasons why cliffs occur at all and how to avoid this.
- Timing belt wear (low quality or technical wear), oil ingress, etc.
- Various foreign bodies get under the belt
- Pump jams
- The tension roller (s) jammed or released
- Seizes the crankshaft or camshaft
In order not to worry about the condition of the timing belt, you must constantly monitor its external condition, the degree of tension, replace it according to the regulations or change immediately if it has any damage. Make sure that oil and other liquids do not get on the belt (this is the beginning of premature wear).
It was once a piston and part of an engine
If, when the timing belt breaks, only the valves are bent, we can say that this is great luck. In some situations, with such a breakdown, the pistons themselves and the surfaces of the cylinders may suffer.
Symptoms and behavior of the car in which it is necessary to replace the timing belt
As a result of increased loads or wear of the connecting rod-piston group, the timing belt can jump one turn, as a result of which,. This phenomenon is a symptom to check the condition of the belt and the correct installation.
Repair cost
Specifically, in each situation, depending on the state of the engine, after stopping it due to a break in the timing drive, auto mechanics will calculate the cost of repairs strictly individually.
Considering the usual example of a broken belt in a K7J engine, the average cost of repair (with materials) will be approximately 10-15 thousand rubles.
"Stick" - the place where the valves and the piston meet cannot be changed.
There were no problems with valve bending when the piston and valve met on VAZ engines - it coped well with its task. But the appearance of front-wheel drive models required new engines, since the Zhiguli engine was with a chain in the block, its dimensions were not suitable for transverse installation. With the help of Porsche specialists, a 1.1 liter engine was developed. with a timing belt and an aluminum block installed transversely. It all started with him.
With the use of the timing belt, there was a risk of breaking it, which means that it could happen " stick". But on the first engines complying with Euro 2, there was no such problem - the belt sometimes broke, but without consequences. The distance between the valves and the piston was sufficient, and during desynchronization, the piston did not reach the valve.
With the advent of Euro 3 standards, a broken belt began to lead to a "meeting" of valves and pistons: the motor, "strangled" by eco-standards, needed to compensate for the loss of power. This can be achieved by increasing the compression ratio. The piston at its top dead center (TDC) has become closer to the valves. It turns out that as a result of the race for better ecology and power, almost all cases of belt breaks began to lead to bending of the valves.
It happens as follows: the timing belt breaks off - the camshaft stops, but not immediately, but turns in the same mode. The piston goes up and meets a stuck valve at TDC. Impact - the valve is bent in a weak spot, under the "plate". The car cannot move further.
In the best case, 1-2 valves suffer, but in the worst case, everything. Repair involves and. The pleasure is not cheap, and most importantly - unpleasant, because who likes to open a generally serviceable engine?
How to avoid
Often " sticklessness»Is achieved by using non-standard pistons with special milled sections on the piston bottom to match the valve shape. VAZ has such engine modifications. As a rule, these are eight-valves. Also, third party milled pistons are used.
The inevitable increase in the combustion chamber, which can cause the engine to dull due to a decrease in the compression ratio, is compensated for by the stamping on the bottom of the piston. However, as practice shows, this measure does not always save the piston and valve from "meeting". We list those motors that, according to the manufacturer, are devoid of the risk of a collision between the piston and valves:
VAZ 2111;
VAZ 21083;
3;
VAZ 21124;
VAZ 2113;
VAZ 11183;
.
But the only reliable remedy is timely. It's just that in the case of a VAZ, it should be done more often than the manufacturer recommends. By the way, there are also “risky” internal combustion engines in foreign cars, but correct operation and timely service negate the negative statistics of “plugs”.
