Forged pistons for different brands of cars

Many technologies are transferred to the motor industry from motor sport. The solutions and parts used there are considered as examples of reliability and productivity, for example, forged pistons. Autotechnology, based on the application of these details, refers to the use of sports solutions on civilian vehicles.

Definition

Pistons are represented by oval-shaped bushes moving in a vertical plane inside the cylinders and compressing the fuel-air mixture. According to the production technology, these parts are divided into cast and forged ones. Let us consider them in more detail.

Features of operation

Pistons of the first type are installed on most cars, as they are well manifested in daily operation and are sufficient for the needs of most users. Forged pistons are designed to work under high loads, so they are used in sports and racing cars. That is, the design and features of this part are determined on the basis of the conditions of its functioning.

The most intense factor affecting the piston when the engine is running is temperature. It leads to an expansion of the metal, which is uneven: it is more apparent parallel to the axis of the piston pin and less in the plane of rocking the connecting rod. As a result, uneven contact of the piston with the cylinder occurs, thereby accelerating wear. In critical cases, seizures appear and the named parts are caught, resulting in the engine jamming.

In addition, the pistons are affected by the inertia force and the pressure created by the gases inside the cylinder.

Production technology

In accordance with the name, casting technology is used to make cast pistons . As a starting material, a silicon-aluminum alloy is used. It is placed in a matrix, giving an oval shape. Then the part is adjusted for the cylinder. The skirt is optimally barrel-shaped. To ensure resistance to high temperatures, the piston is filled from the inside with thermo-compensating inserts made of steel

Unlike cast, forged pistons are produced by punching technology. Apply isothermal or liquid methods.

In the first case, the matrix is filled with molten metal and deformed at a certain rate using a punch. In this way, a high-quality workpiece is obtained. Its final processing is carried out mechanically.

Pre-prepared parts are used for isothermal punching technology. They are obtained from a rod consisting of high-silica aluminum, compressed through a die, which allows to improve the structure of the metal by removing the pores. Further, the preform heated to 450 ° C in the die is stamped using a hydraulic press in a high-speed method. This technology consists in applying a force of 250 tons to the matrix, while maintaining its temperature at a constant level. As a result, precise high-quality parts are obtained.

Main settings

For the competent selection of the parts under consideration for the car, their parameters are correlated with the engine characteristics. Here are the main characteristics of forged pistons:

1. Engine model. The easiest way is to pick up details based on the motor brand, as manufacturers usually create such products for certain engine models. However, it must be taken into account that in this case they are designed for run-off motors. That is, if any engine parameters are changed, for example, cylinders are bored, the pistons calculated for it will not work. Then they are chosen by other parameters (in this case, first of all, in size).
2. The size. When selecting parts, you need to relate their diameter to the diameter of the cylinder, taking into account the temperature expansion.
3. Compression ratio. The technical parameters of the pistons indicate a certain value of this indicator, for which they are calculated. If the engine is not a drain, this must also be taken into account.
4. Weight. The meaning of this parameter of the pistons is discussed below. In general, the less their weight, the better.
5. Power. The technical parameters of the pistons indicate the maximum value of power, which is sufficient for their strength. Do not install the parts on the engine with large characteristics, as exceeding the loads can lead to their accelerated wear and tear.

Differences from cast pistons

The standard analogue of the parts in question are cast pistons. They work properly on standard engines, but for many reasons are not suitable for high-power power units. First, they are characterized by a high mass. Secondly, cast pistons have a non-optimal shape. Thirdly, these details from the plant have defects represented by caverns, foreign inclusions, bubbles that are invisible and do not manifest themselves during normal operation in standard power units.

However, the increase in power leads to an increase in loads (temperature and pressure) on many elements of the car, primarily the engine. Under such conditions, the said defects can lead to cracking or burn-out of the piston. This can happen, for example, after installing the crankshaft with a non-standard crank radius.

Benefits

The positive effect of forged pistons on engine parameters is due, above all, to their small mass. The weight of such a piece is on average 50 g less than a cast analog. For example, forged pistons VAZ provide in the set a saving of mass in 400-600 g. This allows to reduce the inertial forces inside the cylinder. As a result, speed increases, mechanical losses decrease, power increases. In addition, inertial loads on other elements of the crank mechanism, such as crankshaft, connecting rods and liners, are reduced. That is, its common resource increases.

Also forged pistons differ from casters with greater hardness. This indicator is 120-130 units, while for civilian analogues it is equal to 80-90 units.

In addition, these parts are characterized by increased strength and resistance to temperature effects. So, for thermocyclic stability, they exceed the cast analogs 5-6 times. Thanks to this forged pistons withstand 2500 cycles of heating-cooling, while civil models only 400.

The lowered coefficient of thermal expansion made it possible to reduce the thermal gap between the cylinder and the piston to 0.05-0.06 mm.

The form

To reduce the weight, forged pistons have a special shape. In this case, the use of the T-shaped profile does not affect the oil consumption.

In addition, on the basis of uneven temperature expansion (mostly parallel to the axis of the piston pin), some manufacturers produce oval-shaped models perpendicular to the axis of the piston pin. Thus, when heated, the part acquires a circular shape, in accordance with the shape of the cylinder. This ensures a tight fit to each other, evenly distributing the load over the surfaces and limiting the ingress of gases into the crankcase from the combustion chamber.

disadvantages

The main disadvantage of forged pistons, in comparison with cast, consider the high cost, both the parts themselves and the installation. Expensive pistons due to the complexity of production. In addition, you will have to invest heavily in installing them. This is due to the fact that such complex work should be trusted only by professional masters, and in this case it will be necessary not only to install, but also to customize the details.

In addition, it is believed that forged pistons make the car more noisy in comparison with the original cast parts. However, this is only true for a non-heated car. This feature is explained by the differences in the expansion coefficients. Based on this for forged pistons slightly increase the clearance with the wall of the cylinder. Therefore, the unheated engine with these parts works louder. However, after heating, when the pistons expand, and therefore the temperature gap decreases, the noise subsides.

Application

As is clear from the above, forged pistons are used for forced engines. These parts affect many characteristics of power units. They improve both performance and reliability.

Relevance

The expediency of using forged pistons instead of casts is determined, first of all, by the peculiarities of using the car. For the conditions of daily operation, enough cast parts are enough. Forged analogs are usually installed when tuning the engine. And even in this case, their use is not always advisable.

Such details are most often used when forcing low-powered engines. The standard parts of some sports motors have a sufficient resource for non-extreme power increase. Therefore, the most common parts for VAZ engines (for example, forged pistons on the "Niva" and forged pistons on the "Prior").

These parts are used not only for cars. You can install forged pistons on a motorcycle. Tuning sports models is also very common. Sometimes they modify simple motorcycles. For example, some install forged pistons on the "Ural".

Principles of application and cost

Often, the parts in question are used when installing a turbocharger. Moreover, in many cases, their use is a prerequisite for conserving the engine resource, as this increases the temperature and loads on the parts, which often leads to burnout of the pistons. Forged turbo engine pistons are usually used in conjunction with another crankshaft and H-shaped connecting rods.

In any case, during installation it is necessary to ensure cooling of the skirt and bottom of the described part. To do this, install oil spray nozzles.

The price of forged pistons "Niva" (kit), for example, starts at 4 500 rubles. For domestic motorcycles, they will be cheaper.