Intake Valves: What Are They? How Do They Work?

All internal combustion mechanics need air and fuel to operate properly. To do this, there are different holes in the cylinder chamber that are responsible for blowing up this pair of elements and discharging the resulting gases. Those gaps, which open and close continuously in milliseconds, are controlled by the valves. The ones in charge of entering the fuel are the so-called intake valves .

Given that they regulate the access and closure of a liquid or gaseous element to a sealed space that reaches really high temperatures and pressures, the intake valves must be made of very resistant materials and with surgical precision processes. The difference between carbureted and injection engines should be noted : in the former, the air and fuel mixture is made through the intake valve, while in the latter, it is the injectors that shoot the fuel into the cylinder . .

What is an intake valve and how does it work?

In a general definition, an intake valve is one that allows the mixture of air and fuel in the cylinder . Like the exhaust valve, it is designed to open and close at precise times to allow the engine to run efficiently at all rpms. Operation is controlled by lobes (cams) on a rotating shaft ( camshaft ), and is driven by a chain, belt, or gear set from the crankshaft.

Therefore, the intake valve of car engines is responsible for controlling the amount of fuel that enters the combustion chambers. This has a larger size than the exhaust valve motivated by the input conditions when making the mixture, since they are not the same as those of the exhaust gas output; the exhaust valve must withstand higher temperatures than the intake valve (pre-ignition vs. post-ignition), around 700 degrees Celsius (°C) instead of 300 °C.

In multi-cylinder four-stroke engines, the same four cycles are repeated in each of the pistons, but they are sequenced so that the engine delivers consistent power and torque while minimizing noise and vibration. The sequencing of piston, valve and ignition movement is achieved through precise mechanical design and electrical synchronization of the ignition signals to the spark plugs (or glow plugs if diesel), which generate the relevant air-fuel mixture at home exact moment.

What are the intake valves made of and where are they?

Both the intake and exhaust valves are made up of an elongated part, which is known as the valve stem , and an upper part where the head meets . Together with them we find the seat (responsible for the hermetic closure of the cylinder), the key (which joins the spring plate and the valve) and the guides (bushes inserted in the cylinder head that prevent oil accumulation). They are made of alloys , since they must withstand the high temperatures that are reached during the combustion process.

In general, since there have been multiple configurations throughout history, the intake valve is usually located at the top of the cylinders , in the part known as the cylinder head . On the one hand, the valve head is usually attached to this part and is responsible for properly sealing the cylinder. On the other hand, the stem of the lower section is located inside the block itself and its function is to facilitate movement when opening or closing the valves depending on the order of the camshaft.

What types of intake valves are there?

Mainly, we can discern between three types of intake valves:

  • Monometallic valve:are manufactured from a single high temperature resistant material through a hot extrusion or upsetting process (eg mono molybdenum steel).
  • Bimetallic valve:different heat-resistant materials are combined in its construction, placing the most capable in the valve head.
  • Hollow valves:They are used to reduce weight and temperature. They are filled with sodium (melting point 97.5°C), which can dissipate heat from the head to the stem through the stirring effect of the element, and achieve a temperature reduction of between 80°C and 150°C. °C