What does it mean when the exhaust pipe appears entirely red?

[LeJosephine]

The reason the exhaust pipe turns red-hot may be due to the combustion of the air-fuel mixture inside the cylinder within the exhaust pipe, heating it to a glowing state. Below is an analysis of the main reasons why the air-fuel mixture from the cylinder enters the exhaust pipe: 1. Lean air-fuel mixture. An excessively lean mixture can cause slow combustion during the power stroke, continuing to burn into the exhaust stroke, allowing burning gases to enter the exhaust pipe and turn it red. 2. Delayed ignition timing. Late ignition can result in the combustible mixture still burning when the exhaust valve is already open, allowing burning gases to rush into the exhaust pipe and continue combustion there. 3. Poor exhaust valve sealing. If the exhaust valve does not seal properly, burning gases from the power stroke can leak into the exhaust pipe through the poorly sealed valve, heating and turning the pipe red—in severe cases, this can damage the valve. 4. Malfunctioning electronic control system, leading to an imbalanced air-fuel ratio and causing the mixture to become too lean.