What is the reason for the noise after the Audi A6L is turned off?

[MaryLynn]

The noise after the Audi A6L is turned off mainly comes from the three-way catalytic converter, which is the normal sound of thermal expansion and contraction of the catalytic material. In winter, this sound may be more noticeable. This noise is normal, similar to the sound of lightly tapping an iron pipe with chopsticks. More relevant information is as follows: 1. Introduction: The Audi A6L is a mid-to-large-sized car launched by Audi. The height of the engine hood is slightly increased, and the chrome strips in the hexagonal integrated grille are arranged horizontally, combined with the front headlight design, giving the front face a wide and flat visual effect. 2. Configuration: The Audi A6L is equipped with 2.0T and 3.0T turbocharged engines. The 2.0T engine is divided into high-power and low-power versions. The low-power version has a maximum power of 140kW and a maximum torque of 320Nm, while the high-power version has a maximum power of 165kW and a maximum torque of 350Nm. The 3.0T engine has a maximum power of 250kW and a maximum torque of 500Nm.