Purpose, Function
By lengthening the exhaust passage, the transmission of exhaust pressure waves to other cylinders can be delayed, and the amount of gas exhausted from a cylinder and forced back inside the combustion chamber is reduced By reducing the residual gas, the temperature inside the combustion chamber is reduced and the occurrence of knocking even at a high compression ratio is inhibited.
Construction
The exhaust manifold is installed to the rear of the engine. In addition, the catalytic converter (WU-TWC) is integrated (WU-TWC).

When the No.1 cylinder is at the intake stroke, the No.3 cylinder is at the exhaust stroke. By inducing the high temperature gas exhausted from the No.3 cylinder into the No.1 cylinder, the high temperature gas in the No.1 cylinder remains. If the amount of residual gas is high, the temperature in the combustion chamber rises and knocking can easily occur. With the 4-2-1 exhaust system, the transmission of exhaust pressure waves between each cylinder is delayed by the long exhaust pipes.

Exhaust System Removal/InstallationAntenna Feeder No.3 Inspection
1. Disconnect the negative battery cable..
2. Remove the following parts:
a. Front scuff plate.
b. Rear scuff plate.
c. B-pillar lower trim.
d. Front seat belt adjusting cover.
e. Front seat belt upper anchor installation bolt.
f. B-pillar upper trim.
g. Rear seat cushion.
h. Trunk ...
Rear Door Checker Removal/Installation
1. Fully close the rear door glass.
2. Disconnect the negative battery cable..
3. Remove the rear door trim..
4. Remove the rear door speaker..
5. Remove bolt.
6. Remove nuts.
7. Pull out the rear door checker from the rear speaker installation hole.
8. Install in the reverse ...
Seat Weight Sensor Control Module Removal/Installation [Two Step Deployment
Control System]
CAUTION:
When the seat weight sensor control module is replaced with a new one, perform
the seat weight sensor calibration using the M?MDS..
1. Switch the ignition to off.
2. Disconnect the negative battery cable and wait for 1 min or more..
3. Disconnect the connectors.
...