How to Choose the Right Car for You | Buyer's Guide & Info
Car Reviews, Have free Car Technical Specifications, Car User and Repair manuals,Car Oil change Catalog and Recommendations,Responses of car owners

Gas distribution mechanism Types

0 23

In this article we will consider the existing types of gas distribution mechanisms. This information will be very useful to motors, especially those who repair their cars on their own. Well, or trying to repair them.

Each Gas distribution mechanism is actuated from the knee shaft. Force transfer can be performed by belt, chain or gear. Each of these three Gas distribution mechanism types has advantages and disadvantages.

Let ‘s take a closer look at the types of Gas distribution mechanism drive

  1. The belt drive has little noise during operation, but does not have sufficient strength and can break. The consequence of such a break is bent valves. In addition, the weak tension of the belt leads to the possibility of its skipping, which risks phase shift complicated by starting. In addition, the downed phases will give unstable idle operation, and the engine will not be able to operate at full power.
  2. The chain drive can also make a “jump,” but the probability of it is greatly reduced due to the special tensioner, which is more powerful in the chain drive than in the belt drive. The chain is more reliable but has some noise, so not all car manufacturers use it.
  3. The gear type of the Gas distribution mechanism was mass-applied for a long time, in those times when the distribution shaft was located in the ICE unit (lower engine). Such motors are now little common. From their advantages it is possible to note cheapness of manufacture, simplicity of design, high reliability and practical eternal, non-replacement mechanism. From the disadvantages – small power, which can be increased only by increasing the volume and, accordingly, the size of the structure (for example – Dodge Weiper with a volume of more than eight liters).


What is it and why? The distribution shaft is used to adjust the moment of opening of valves, which at the inlet supply fuel to cylinders, and at the phase of exhaust remove exhaust gases from them. Eccentrics are specially arranged on the camshaft for this purpose. The operation of the camshaft is directly related to the operation of the crankshaft, and due to this fuel injection is carried out at the most useful moment – when the cylinder is located in its lower position (lower dead center), i.e. before the start of the inlet path.

The distribution shaft (one or more – not important) can be located in the HBC, then the motor is called the “upper” one, and can be located in the cylinder block itself, then the motor is called the “lower” one. It was written above. They are usually equipped with powerful American pickups, and some expensive cars with a giant engine volume, oddly enough. In such power units, the valves are driven by bars running through the entire engine. These motors are slow and very inertial, actively consuming oil. Lower engines are a dead end branch of motor structure development.

Types of gas distribution mechanisms

Above we have considered the types of Gas distribution mechanism drives, and now we will talk about the types of the gas distribution mechanism itself.

SOHC Mechanism

The name literally denotes “one upper camshaft.” It used to be called simply “OHC.”

Such an engine, as is already apparent from the name, comprises a single camshaft disposed on the cylinder head. Such an engine may have both two and four valves in each cylinder. That is, contrary to various opinions, the SOHC motor may also be sixteen-valve.

What are the strengths and weaknesses of such motors?

  • The engine is relatively quiet. Silence is relative to the two-way motor. Although the difference is not big.
  • Simple design. Which means it ‘s cheap. This also applies to repair and maintenance.
  • But from the disadvantages (though very insignificant) it is possible to note weak ventilation of the motor equipped with two valves per cylinder. Because of this, the engine power drops.
  • The second minus has all sixteen valve motors with one distribution shaft. Since the distribution shaft is one, all 16 valves are operated by a single distribution shaft, which increases the load on it and makes the entire system relatively brittle. In addition, because of the low phase angle, the cylinders are worse filled and ventilated.

DOHC Mechanism

Such a system looks almost the same as SOHC, and features a second distribution shaft installed next to the first. One camshaft is responsible for actuating the intake valves, the other of course the exhaust valves. The system is not ideal, and has, of course, its disadvantages and advantages, their detailed description goes beyond the scope of this article. DOHC was invented at the end of the last century, and did not change after that. It should be noted that the second camshaft makes the design of such an engine much more complicated and expensive.

But for that, such an engine consumes less fuel at the expense of better filling of cylinders, after which almost all exhaust gases leave them. The appearance of such a mechanism significantly increased the efficiency of the engine.

OHV Mechanism

Above, this type of engine (lower) has already been considered. We invented it at the beginning of the last century. Distribution shaft in it is located at the bottom – in block, and rockers are used to drive action of valves. From the advantages of such an engine, a simpler HBC device can be distinguished, which allows V-shaped lower engines to reduce their size. We will repeat the disadvantages: low speed, high inertia, low torque and weak power, inability to use four valves per cylinder (except for very expensive cars).

Let ‘s sum up

The mechanisms described above are not an exhaustive list. Motors rolling more than 9,000 revolutions, for example, do not use springs under valve plates, and in such engines one spread shaft is responsible for opening the valve and the second for closing, which allows the system not to hang at revolutions above 14,000. Mainly such a system is used on motorcycles with a power above 120 hp.

Leave A Reply

Your email address will not be published.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More