It is possible to repair the engine after a timing belt break, but you will have to spend a lot of effort, money and time on this. Therefore, many car owners do not wait until the belt breaks and the pistons meet the valves, and immediately install other, protected pistons. “Priora” with the same details works the same way as with the factory ones. But the risk of breakdown due to a broken timing belt is reduced to almost zero.
Now there are several manufacturers that produce parts for this engine, including pistons. Priora is equipped with products from the Russian companies STK, STI and Avtramat from a Ukrainian manufacturer. Let's see what these products are.
general information
The piston in the internal combustion engine is designed to transmit rotational energy to the crankshaft. This energy is produced by the combustion of the mixture. When a mixture of air and gasoline explodes, the expansion of gases occurs. The latter press on the surface of the part and push it. During operation, the piston surface experiences high heat loads. The pressure in the Priors motors can reach 65-80 bar.
During operation, the Priors pistons are accelerated to a speed of 100 km / h with a certain frequency and then decelerated to zero, while the operating frequency of 6000 rpm is 200 Hz. When the fuel-air mixture burns, the heating in the chambers can reach 1800-2660 degrees. This is several times higher than the temperature at which the metal melts. As a result, the strength of the alloy is reduced. Various stresses arise in the piston body due to sharp temperature jumps, and in addition stress from pressure and inertia is added during accelerator-deceleration processes at high frequencies.
Device
So that the crank assembly can serve in such difficult conditions, the part must be lightweight and resistant to wear. The alloy has high thermal conductivity - due to this, the cooling rate during heating is ensured.
The outer surface is formed in such a way that there is never a risk of jamming of the part inside the combustion chamber. Gases must not enter the crankcase. Due to the temperature difference between the piston bottom and the skirt, the element is made in a barrel-shaped form. Therefore, it satisfies all the requirements.
To compensate for the deformation of the skirt during operation, the mechanism is made with the so-called "anti-ellipse". The major axis of the part is perpendicular to the finger hole. The upper part of the piston is the so-called head. It has a bottom and special grooves. O-rings are installed in them. So that the piston head can withstand high loads, a special protective coating is applied to it.
Piston ring grooves are made at a slight angle. This ensures the position of the outer edges of the rings is higher than the inner ones. The manufacturer prevents the tilting of the cross section of the groove down at high temperatures. This is not the last characteristic that distinguishes pistons. The Priora is equipped with elements that “slide” in the combustion chamber. To do this, their working surface is covered with special compounds. To make the part better run in, coatings are applied, which will eventually wear out during the break-in process. This is often a phosphated tin compound. This coating also reduces the occurrence of scratches during cold start. Anti-friction materials remain on the piston forever. They prevent cracking of the working part of the part and erosion.
The piston skirt in the production is processed with special cutters to create a microrelief. So the oil is better retained on the surface, thereby reducing friction on the pistons. "Priora" will withstand heavy loads on KShM. Third-party pistons correspond equally to all of these parameters. Products "STK" is very weighty - say the reviews. They are heavier than all other models.
Reasons to replace
Everything is very individual here. Motorists argue that if you fully comply with all regulations regarding maintenance, install parts from the original manufacturer or just high-quality analogues on the Lada Priora, then the engine will never let you down. Everything will work as usual. But everyone wants to save on spare parts or to make Priory tuning. This raises questions. For example, if you save on the gas distribution mechanism by installing low-quality rollers and a belt, then the replacement interval is slightly reduced. For example, the standard timing belt is supposed to be changed every 50 thousand km. On non-original spare parts, you can drive only up to 10 thousand km.
STI pistons
STI is a Togliatti company. Pistons are made using hot pressing technology. If we analyze the reviews of all those who have already bought spare parts of this brand for the Lada Priora car, we can see that they greatly reduce the efficiency of the motor. This can be explained by the fact that, compared with the production of STK and Avtramat, STI parts have a lower compression ratio. The combustion chamber has a large area due to too deep sampling for the valves.
The composition of the alloy reduced silicon content. This affects the strength characteristics of the part at high thermal loads. The reduced amount of nickel makes the part resource lower. With these drawbacks, these pistons have a high price. But at the same time, the forged products from the STI company significantly lose to other brands. The Avtramat pistons (Priora manned by them too) are devoid of these shortcomings, as are the STK. However, there were cases of belt breaks on cars with these mechanisms.
Avtramat
These are the details of Ukrainian production. Pistons are made at the Kharkov enterprise. The part is cast. The alloy completely repeats that of the original parts. The factory dimensions of the VAZ pistons are also repeated. But unlike the original, the Ukrainian element has deeper selections. This gives him a lot of advantages over the standard part if the timing belt breaks. As for the compression ratio, it remained unchanged. Therefore, if you install these products, the difference in power characteristics of the engine will not be noticeable.
Due to the fact that the samples were increased, the area of the combustion chamber increased slightly, the efficiency should be lower relative to standard spare parts. However, the numbers differ slightly. So, the figure is 53.2 cm 2 for the original and 53.3 cm 2 for Avtramat. In practice, this is completely invisible. There is another plus that these pistons have. "Priora" (the price of parts is 3 times less - 2 thousand rubles than for products from "STI" - almost 7 thousand) in maintenance will cost inexpensively if you use these products.
STK
These parts are manufactured at the enterprise in Samara. Their technical characteristics practically do not differ from the Avtramat products. The difference in piston weight. Due to the higher weight, the acceleration dynamics of the car is reduced. Also, STK pistons have a higher price.
Advantages of installing non-standard pistons
Elements with grooves under the valves are very hardy. Even if the timing belt breaks, the upper camshaft and valves will simply freeze in place. The piston will go down due to the crankshaft, and nothing bad will happen. The valves will fall into the grooves created for them. Next, the owner will need to drive the car to the service station, where specialists will restore the timing mechanism. This is a huge plus.
Note that if there are no these grooves on the pistons, then a serious repair awaits as a result of a break in the owner's belt. The pistons and valves, as well as the camshaft pastel, are directly replaced. The cost of such repairs can start from 30 thousand rubles. Therefore, it is worth installing the STK pistons or the like. Grooves will save from expensive repairs.
Minuses
If the piston is light (as much as possible), then the motor will increase in power. It is possible to achieve an increase in dynamic characteristics by 5-7%. Pistons with grooves cannot be called light. To make a recess in the upper part of the part, you need to have a sufficiently thick wall. This makes it harder, because of which power is lost.
In addition, these grooves change the compression of the combustible mixture. This also affects the traction of the power unit. If to summarize, then with the installation of such a part, the same 5% of power will disappear from the motor. For an engine of 150 liters. from. these are 10.5 "horses". Another drawback is the greater fuel consumption. The dimensions of the VAZ pistons are the same as the factory ones, but due to the grooves the volume of the combustion chamber increases, even if only slightly. Finally, because of the increased volumes, the compression drops. Detonation is also increasing.
Conclusion
With all the shortcomings, car owners still install non-standard pistons with grooves. This allows you to protect the motor in the event of a broken timing belt. According to motorists, the best pistons on the Priora are the Avtramat products. They have the best price, weight and characteristics.