If your engine is the heart of your vehicle, the combustion chamber is where the magic happens. This critical space inside each cylinder is where air and fuel meet under high pressure and ignite, creating the power that drives your car forward.
A clean, efficient combustion chamber affects engine responsiveness, fuel economy, and emissions. Car owners should pay attention to this detail to improve performance and keep their daily drivers running smoothly.
What is a Combustion Chamber?
A combustion chamber is a part of the internal combustion engine in which the combustion of the air-fuel mixture takes place. This is an enclosed cylinder.
The combustion chamber of the reciprocating engine has a piston. This piston reciprocates inside the chamber to compress the air-fuel mixture.
As the mixture is compressed, a spark plug (in an SI engine) generates a spark and ignites the compressed air-fuel mixture. The air-fuel mixture ignition process inside the combustion chamber greatly increases the chamber’s inner temperature and pressure. After the ignition process, the piston expels the combusted mixture out of the chamber.
The IC engine combustion cylinder contains many parts, such as a fuel pump, fuel nozzles, a spark plug, and a piston.
The combustion chambers are most commonly used in the engines of cars, ships, airplanes, buses, trucks, and many other vehicles. If you have an automobile or car, you can easily find it there.
Types of Combustion Chamber Shapes
Depending upon the location of the spark plug, valves, and type of cylinder head, the combustion chambers are of the following shapes:
- Spherical shape
- I-shape
- T-shape
- F-shape
- L-shape
#1. Spherical Shape Combustion Chambers.
The combustion chamber is almost hemispherical in shape; the engine possessing such a combustion chamber is called a hemispherical engine. The inlet and the outlet valve of the engine are situated on the wall of the hemisphere.
The situation of the spark plug may vary; when the spark plug is situated on the top, it gives a high compression ratio, and when the spark plug is situated on the side, it gives a low compression ratio.
When the spark plug is situated on the side, the engine offers better scavenging. Generally, combustion chambers with a sparkplug situated on the top are used.
#2. I-Shape Combustion Chambers.
In the I-shape combustion chambers, overhead valves are used. A spark plug may be fitted at the center or the side of the cylinder head.
The engines having this type of combustion chamber are used in high-speed vehicles and racing cars. These engines are cheap.
#3. T-Shape Combustion Chamber.
The T-shaped combustion chamber is simple in construction. It projects around the cylinder head. The spark is fitted at the top and the valves at the sides. The engines having such combustion chambers have good efficiency.
#4. F-Shape Combustion Chamber.
F-shape combustion chamber projects at one side of the cylinder head. The location of the spark plug and valves.
#5. L-Shape Combustion Chambers.
L-shaped combustion chambers used side valves. The engines with such combustion chambers are used in slow and medium-speed cars.
Types of Combustion Chambers for Diesel Engines
Other types of combustion chambers for diesel engines are as follows:
- Open combustion chamber
- Pre-combustion chamber
- Swirl combustion chamber
- Squish combustion chamber
- Air cell and energy cell
- Energy cell combustion chamber
#1. Open Combustion Chamber.
The open combustion chamber is used in medium and high-speed engines. The combustion chamber is made in the form of a groove inside the top of the piston.
The injector is fitted at the center of the cylinder head so that it injects the fuel into the combustion chamber. The engines of Leyland buses use this type of combustion chamber.
#2. Pre-Combustion Chamber.
The pre-combustion chamber is usually used in high-speed engines. There are two combustion chambers: one is the auxiliary combustion chamber, and the other is the main combustion chamber.
This auxiliary chamber is smaller in size than the main combustion chamber and is called the pre-combustion chamber.
The fuel is injected into the pre-combustion chamber, where it is partly burned. This partly burnt fuel goes into a small hole in the main combustion chamber, where the complete combustion takes place.
The turbulence is created in the combustion chamber. The chamber helps to ignite the fuel completely.
Sometimes, a glow plug is fitted in the pre-combustion chamber, which is heated by electricity. It helps to ignite the combustion chamber.
#3. Swirl Combustion Chamber.
The swirl combustion chamber is also known as the turbulence combustion chamber. Swirl is a circular motion that is transferred to the incoming air during the suction stroke.
In the swirl combustion chamber, the air is given a swirl while coming into the cylinder. The fuel is injected into this swirled air so that the mixing and burning of fuel takes place completely.
#4. Squish Combustion Chamber.
Squish is a flow of air that goes from the periphery to the center of the cylinder. To get a swish combustion chamber, a groove is made inside the piston head.
During the compression stroke, when the piston moves from BDC to TDC, it squeezes the air from its periphery towards the centre.
This action gives turbulence to the air. The fuel is injected at the center of the combustion chamber. Sometimes, the squish combustion chamber is made inside the cylinder head.
#5. Air Cell Combustion Chamber.
The air cell is a small combustion chamber connected through the air in a narrow passage with the main combustion chamber. During the compression stroke, the air is compressed in the air cell.
When the fuel is injected into the combustion chamber, it burns, and the piston moves down. At this time, the compressed hot air of the air cell comes into the main combustion chamber, creating turbulence and ensuring complete combustion.
Air cells are used mostly in high-speed engines. Like the pre-combustion chamber, the air cell requires a heater plug to heat the compressed air.
The engines with air cells require a high compression ratio. There is more heat loss due to the increased surface area of the cylinder with the air cell.
#6. Energy Cell Combustion Chamber.
The energy cell is also known as the Lanova combustion chamber. It operates on the principle of a Pre-combustion chamber and air cell.
The energy cell is connected through a narrow passage with the main combustion chamber and consists of a major cell and a minor cell. These two cells are connected by a narrow opening, which can be closed by a plunger.
At the time of starting the engine, the narrow opening is kept closed, which increases the capacity of the combustion chamber.
When the engine is started, the narrow opening is opened, which connects the major cell with the minor cell. When the fuel is injected into the main combustion chamber, some part of it, about 10%, goes into the energy cell also.
The combustion takes place first in the main combustion chamber and then spreads up to the energy cell, where pressure increases.
As the piston moves down, the hot gases from the energy cell come into the main combustion chamber due to the pressure difference, creating turbulence and ensuring complete combustion.
Bowl-in piston Combustion Chamber
A high compression ratio gives high power to a spark-ignition engine; there has been a tendency for combustion chamber shapes at T.D.C. to resemble flat discs.
Also, very close tolerances have become necessary to ensure that the compression ratios of all cylinders of an engine are identical. This has led to the bowl-in piston combustion chamber, as in Rover 2,000, Ford V-four, V-six, and Jaguar V12 engines.
With this arrangement, a compact combustion chamber is obtained in which relatively close control of turbulence is possible.
Also, the maintenance of close tolerances between the flat top of the piston and the flat lower face of the cylinder head is not too difficult surfaces are easy to machine all over.
The top surface of the piston is recessed to accommodate the valve faces. The spark plug is as close as practicable to the center to obtain a uniform spread of the combustion flame. The rate of heat transfer to the piston is greater than with more conventional designs.
Why Temperature Control Matters?
If the combustion temperature gets too high, it can lead to engine knocking, pre-ignition, or internal damage like cracked pistons or warped heads. Conversely, low temperatures can result in incomplete combustion, higher emissions, and carbon buildup.
Keeping your combustion chamber car unit clean protects your engine from temperature extremes. Deposits act as insulation and create hot spots, disrupting the ideal burn cycle. Clean chambers help maintain consistent, controlled temperatures.