Why is the Mazda cold start sound so loud?

[MacPhoebe]

Mazda cold start noise is loud for the following reasons: 1. 421 exhaust system: This is the main cause of the loud cold start noise in Mazda engines. The noise primarily comes from the exhaust position, while the engine itself is relatively quiet. 2. Oil viscosity: When the engine is cold, the oil is cold and thick, resulting in high operating resistance. The design of major components like pistons and cylinders is based on the assumption that they will expand due to heat, so the gaps between parts are not optimal before warming up, which is why the engine noise is loud during the initial idle. 3. Increased RPM: The design of the 421-style exhaust pipe makes it longer, and the catalytic converter is placed farther from the combustion chamber. Since the catalytic converter needs to reach a certain temperature to function effectively, a new idle system is introduced. Within 20 seconds of starting, a small amount of mixed gas burns in the exhaust pipe, producing a 'whooshing' sound.