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/InstallationMass Air Flow (MAF) Sensor Inspection
Visual Inspection
1. Remove the MAF sensor/IAT sensor No.1..
2. Visually inspect the MAF sensor for the following:
Damage, cracks, soiling
Rusted sensor terminal
Bent sensor terminal
If there is any malfunction, repair or replace the MAF sensor/IAT sensor
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Main Relay Control [Skyactiv G 2.0]
Outline
Supplies power to each part by switching the main relay on/off at the optimal
timing according to the vehicle conditions.
Block Diagram
Operation
When the ignition is switched ON, the main relay turns on and electrical
power is supplied to each sensor and devic ...
Air Intake Actuator Inspection [Manual Air Conditioner]
1. Connect battery positive voltage to air intake actuator terminal B (or C),
connect terminal C (or B) to ground, and then verify that the air intake actuator
operates as shown in the table.
If the operation condition is not normal, replace the air intake actuator.
...