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/InstallationWheel Alignment Pre Inspection
1. Park the vehicle on level ground, in an unloaded condition*, with the wheels
straight forward.
*: Unloaded condition.....Fuel tank is full. Engine coolant and engine oil are
at specified level. Spare tire, jack and tools are in designated position.
2. Inspect the tire pressure.
...
Front Tilt Motor Inspection
WARNING:
Handling a side air bag improperly can accidentally operate (deploy) the
air bag, which may seriously injure you. Read the service warnings/cautions
in the Workshop Manual before handling the front seat (side air bag integrated)..
CAUTION:
When performing the pro ...
Wiper/Washer System Personalization
A customize function has been adopted which switches the auto wiper system
between operable/inoperable.
Using Mazda Modular Diagnostic System (M-MDS)
The auto wiper function can be enabled or disabled using the Mazda Modular
Diagnostic System (M-MDS). Refer to the Workshop M ...