How to Determine Whether the Air-Fuel Mixture is Too Rich or Too Lean?
1 Answers
Methods for determining whether the air-fuel mixture is too rich or too lean are as follows: 1. Symptoms of a too-lean mixture: Carburetor backfire, difficulty starting, engine overheating, detonation in the cylinder, reduced power, improvement of the above symptoms when the choke is closed, knocking sound during acceleration, unstable idle speed prone to stalling, and very white spark plugs. 2. Symptoms of a too-rich mixture: Exhaust pipe popping with black smoke and possibly oil droplets, engine overheating, insufficient power, unstable operation, increased fuel consumption, muffled engine sound, weak acceleration, unstable idle speed, and severely blackened and carbon-fouled spark plugs. 3. Rich mixture: When the excess air coefficient is between 0.85 and 0.95, the flame propagation speed is the highest, resulting in the fastest combustion rate. This allows the cylinder pressure and temperature to reach their maximum values in a short time, with minimal heat loss and maximum work output. Since the fuel supply at this point is slightly more than required for complete combustion, with a fixed air volume, the utilization of oxygen is enhanced, increasing the number of combustion product molecules and raising the gas pressure. Consequently, the engine delivers its maximum power. Such a mixture is referred to as the maximum power mixture.
