What happens to the EGT and cylinder head temperature when the mixture is weakened?

When the mixture is weakened, which means the fuel-to-air ratio is reduced, the engine experiences a few notable thermal changes. The exhaust gas temperature (EGT) tends to decrease because the richer mixture typically burns more completely, generating more heat. When the mixture is weakened, there is less fuel available for combustion, leading to less thermal energy produced in the combustion process.

Simultaneously, the cylinder head temperature (CHT) usually increases. This occurs because, with a weaker mixture, the cylinder may run hotter. Since there is less fuel to absorb heat during the combustion process, the cylinder head can overheat, causing an increase in temperature.

In summary, when the mixture is weakened, the exhaust gas temperature decreases while the cylinder head temperature increases. This understanding highlights the relationship between fuel mixture and thermal dynamics in reciprocating engines.