What features are expected of carburetor systems and what should they be? What are the negative aspects of a mixture that is rich or poor?
- It is easy to move in the cold.
- Supplying the required fuel-air combination in any working range
- You must ensure that the fuel has been fully pulverized before it is mixed with the intake air to create a homogeneous mixture.
- Provide the necessary mixing ratio for sudden accelerations
- When the engine is at idle, as much economy as possible
- It is easy to disassemble, clean and adjust so that you can easily meet your cleaning and service needs.
The engine will experience problems if the carburetor mixture is too rich or lean. Mixtures under the condition of excess air coefficient λ > 1.15 are defined as very lean mixtures and the following disadvantages occur when starting the engine with a mixture under these conditions:
- Due to incomplete combustion of the cylinder, burning times will be extended in lean mixtures. The exhaust also causes flame rebound.
- After the exhaust period ends, excessive heat can cause the seating surfaces of exhaust valves to burn.
- This can lead to an increase in temperatures, uncontrolled ignition and knocking especially around the exhaust valve.
Too enrichment of the mixture causes the following disadvantages to occur in starting the engine with a mixture that meets the conditions of approximately λ < 0.84:
- Soot is produced on the combustion chamber wall and piston top. The piston, ring, and cylinder surfaces are more susceptible to wear.
- In other words, soot is the accumulation of carbon on the walls of the combustion chamber that causes uncontrolled ignition.
- Uncomplete combustion results in an increase of harmful CO, unburned HP and other pollutants from exhaust gas emission. It can lead to increased air pollution.
- The viscosity in the cylinder walls is affected by excess gasoline, particularly during warm-up. This increases wear by thinning the oil film in the cylinders under boundary lubrication conditions.
- The engine’s combustion efficiency will drop, which will cause an increase in fuel consumption.
The order in which the Otto engines operate will dictate the order of the required mixing ratios. It is important to determine the limits of variation in the mixture ratio (also known as the mixture characteristics) under different operating conditions.
