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/InstallationIon Sensor
Purpose/Function
Detects ion generation in the combustion chamber for detecting pre-ignition.
Detects ions which occur due to fuel combustion as current by applying bias
voltage to the spark plug, which is amplified in the ignition coil internal
circuit and input to the PCM.
...
Refrigerant Pressure Sensor [Full Auto Air Conditioner]
Purpose
The refrigerant pressure sensor detects the refrigerant pressure in the refrigerant
cycle.
Function
The refrigerant pressure sensor converts the detected refrigerant pressure
to an electric signal and sends it to the PCM.
Construction
The refriger ...
Rear Upper Arm Removal/Installation [Awd]
WARNING:
Verify that the crossmember is securely supported by a jack. If the rear
crossmember falls off, it can cause serious injury or death, and damage to the
vehicle.
CAUTION:
Performing the following procedures without first removing the rear ABS wheel-speed
...