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/InstallationCrankshaft Position (CKP) Sensor Inspection
Visual Inspection
CAUTION:
When foreign material such as an iron chip is on the CKP sensor, it can cause
abnormal output from the sensor because of flux turbulence and adversely affect
the engine control. Be sure there is no foreign material on the CKP sensor when
replacing.
...
Evaporator Temperature Sensor Inspection [Manual Air Conditioner]
NOTE:
Inspect the evaporator temperature sensor when it is installed to the A/C
unit.
1. Set the fan speed at MAX HI.
2. Set the temperature control at MAX COLD.
3. Set the RECIRCULATE mode.
4. Turn the A/C switch off.
5. Close all doors and windows.
6. Wait for 5 min.
7 ...
Auto Dimming Mirror Inspection
1. Measure the voltage at each terminal.
If the voltage is not as specified in the Terminal Voltage Table (Reference),
inspect the parts under “Inspection item (s)” and related wiring harnesses.
If the system does not work properly even though the inspection items
or ...