What are the advantages of 8-and 16-valve engines?


Most budget cars are equipped with four-cylinder engines, and even in the premium class, high-performance units of similar design gradually begin to appear.

16 клапанный и 8 valve engine

Such an engine can be equipped with various intake systems involving the use of eight or sixteen valves. They are mainly used on different machines, but some manufacturers, including Renault and AvtoVAZ, offer the buyer a choice of two options.

Читать далее, какой двигатель лучше, 8- или 16-клапанный-->Чтобы сделать правильный выбор, нужно знать, какая конструкция лучше: 8 или 16 клапанов, и в чём преимущества каждой из них.

Simple and reliable

On inexpensive cars most often there are engines with 8 valves - this means that for each cylinder there is one opening for the intake of the gas-air mixture and one for the production of exhaust gases. Such motors are always equipped with one camshaft, which is driven by a fairly simple mechanism based on a belt or chain. That is why the repair and maintenance of an 8-valve engine is much cheaper - even with a serious breakdown, there are much fewer parts to change. It is better to choose such a motor for operation in difficult conditions, where it is rather difficult to find qualified assistance.

8 valve engine Лада

8 valve engine

The difference also lies in the simplified design - as a rule, manufacturers try to save on the production of engines with 8 valves and use a rather primitive scheme with manual adjustment of the thermal gaps. Of course, this can be called a minus, since such work can take a lot of time, and a knock on the part of the intake system can appear very unexpectedly.

However, an engine lacking automatic hydraulic compensators is not so sensitive to the quality of the oil poured into it and can run on not very high quality gasoline without the risk of a quick breakdown. In addition, the difference lies in the smaller geometrical size of the valves. Therefore, in the presence of special grooves in the pistons, an open timing belt is not terrible for the engine - the valves will simply fall into them, which will prevent its serious damage.

Timing belt 8-valve engine

Among the advantages of engines with 8 valves can be called the smaller dimensions of the intake system, which allows easier access to many mounted units such as a generator and a starter. Specialists working in the workshop confirm this fact - they say that it is much more convenient to repair the eight-valve units. However, the difference may lie not only in this, but also in the need for periodic tension of the timing belt with the help of a special mechanism.

You do not have to do this manually, but you need to carefully monitor the coincidence of the position of the belt and camshaft to prevent loss of timing synchronization. Therefore, it is advisable to service the engine with 8 valves on a budget car every 20 thousand kilometers in order to maintain its optimal settings.

However, engines with 8 valves are distinguished not only by the simplicity and low cost of maintenance. If we recall the geometry, we can conclude that whatever the diameter of the two valves, it will still remain smaller, their total area will still be smaller than that of the four.

Engine 8 valve Renault

Such a difference leads to the fact that the gas-air mixture enters the cylinders more slowly, and the exhaust gases need more time to leave the engine. Accordingly, the engine is not so eagerly gaining momentum and reacts a little more slowly to the fuel supply. Therefore, if you buy a car for a dynamic ride, it is better to refuse an eight-valve power unit.

In addition, motors with a smaller number of valves do not work as steadily as this especially concerns a design that is so unbalanced from the point of view of vibrations, like a four-cylinder power unit. Therefore, when accelerating rapidly, the driver can be annoyed by a fairly strong noise, and at low revs the car can shudder from the vibration waves passing through its body. However, there is good news for owners of cars with eight-valve motors - they work better at low revs and provide better traction. That is why such a car should be purchased for work with a trailer or for driving on roads with difficult terrain.

Greater efficiency

The main advantage of a sixteen valve engine is the greater throughput of its intake system. Four circles, inscribed in another, having a larger diameter, have an increased total area compared to two. This means that more air-fuel mixture penetrates into the cylinders per unit of time and more exhaust gases are discharged. Accordingly, the combustion processes proceed much better, which makes it possible to obtain an increase in power of approximately 15–20% in comparison with eight-valve units. This difference also affects comfort. Discounts for new cars! Profitable loan from 9.9% installments 0% adom.ru - it is possible to significantly reduce the intensity of noise and vibrations.

16 valve engine Лада

16 valve engine

In addition, the sixteen-valve engine is better than its counterparts, since it is much more often equipped with hydraulic compensators. Manually adjusting the thermal clearances on such a large number of valves is time consuming and ungrateful. Even the slightest mistake can lead to the fact that the optimal settings will be lost and the motorist will have to perform all the work again. Of course, the use of such parts makes the engine very sensitive to the quality of oil and fuel. In the presence of a large amount of impurities, the hydrocompensators quickly become clogged with carbon, which leads to accelerated wear and failure.

The same is true of the timing mechanism - it does not need to be adjusted until the complete replacement of the belt. Among the advantages should be noted and lower fuel costs. This is partly due to the optimized combustion process of the mixture in the cylinders, and partly due to the greater "elasticity" of the engine and the accelerated exit to the desired mode of operation. The difference in the design with 16 valves is also in the use of more complex techniques. In practice, this leads to an increase in the labor intensity of repair and an increase in the cost of spare parts.

Timing Belt 16-valve engine

If you are thinking about which engine to choose when buying a car, you should evaluate the conditions in which it will be used. If we are talking about operating away from major cities and professional service stations, it is better to purchase a vehicle with an eight-valve engine. Of course, an 8-valve motor often needs adjustment and is less efficient, but maintaining it yourself will not be a significant problem.

Engines with 16 valves are more powerful and more economical at the same time, but they require the use of exceptionally high-quality fuel and oil, and also need costly repairs with serious damage. Therefore, it is better to buy them for those who love active driving style, and can also at any time apply for qualified technical assistance.

Security questions

In various forums and other thematic resources one has to read a lot of messages in which there is a debate about the safety of eight-valve and sixteen-valve engines. So, the majority of VAZ car owners claim that they are afraid to purchase cars with 16 valves due to the fact that a belt break in them inevitably leads to an overhaul of the engine. To finally resolve the dispute about the valves, it is worth saying that the possibility of a collision with the pistons does not directly depend on the design.

Video comparison of 8-and 16-valve VAZ engines:

It has already been said above that the difference between motors with different numbers of valves lies in the geometric size of the intake system. Accordingly, the eight-valve engine is much easier to make safe by preventing damage when the belt is broken. To do this, it is enough to provide the piston with small grooves, which will receive the fallen valves. On VAZ cars, all eight-valve constructions are safe from this point of view. The only exception is the power unit, which is equipped with a shortened piston group manufactured by Federal Mogul - there really is a danger of serious damage leading to a major overhaul.

Domestic-made sixteen-engine engines are mostly vulnerable to the timing belt break, but this does not at all concern the most modern engines installed on the Priora, Grant and the modernized Kalina. The most dangerous engines are 1.6 liters, which were installed on the VAZ-2110. In addition, there is the likelihood of collision of valves with pistons and on a small-batch engine with a volume of 1.8, which is installed on tuning cars of domestic production.

Timing belt breakage

Open timing belt on a 16-valve engine

If we talk about foreign cars, then engines that are equipped with timing belts are considered safe on cars of the following brands:

  • Hyundai и KIA;
  • BMW;
  • Toyota;
  • Some Chevrolet models.

If you are wondering which car is safe from the point of view of a timing belt break, you should first spend time studying specialized resources. But the car brands such as Mazda, Renault, Honda, Daewoo and some others can cause serious problems with the breakdown of the gas distribution mechanism. However, you should not be afraid of this - it is enough just to change the belt according to the established schedule, and also periodically check its condition.

The best way

The difference between engines with different designs of the intake system is that the sixteen-valve units have more power, but require better maintenance. Eight valves are very unpretentious, however, they consume more fuel, are noisy and do not allow to achieve equally good accelerating dynamics.

8- and 16-valve engine

Therefore, the first option is suitable for those who prefer dynamic food and are willing to spend money on repairs, as well as on the purchase of exceptionally high-quality oil and fuel. In addition, sixteen bladed units will be ideal for tuning - including the installation of the turbine. But the eight-valve engines are well suited for machines that perform the functions of "workhorses" due to maintainability, good low speed and low cost parts.