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/InstallationForced Ignition On
NOTE:
In order to perform a forced ignition ON, the M-MDS is necessary. If the
servicing is being done outside of an Authorized Mazda dealership, contact an
Authorized Mazda dealership for instructions.
The forced ignition ON procedure forces a power supply to each part when
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Liftgate Hinge Removal/Installation
1. Disconnect the negative battery cable..
2. Remove the following parts:
a. Rear scuff plate.
b. Trunk end trim.
c. Trunk side trim.
d. C-pillar trim.
e. D-pillar trim.
f. Liftgate.
3. Remove fasteners.
4. While partially peeling back the rear part of the headliner, remove nut ...
Evaporative Emission (Evap) Control System
Purpose, Outline
Prevents release of evaporative gas into the atmosphere.
The intake manifold vacuum introduces evaporative gas to the intake manifold
via the charcoal canister and the purge solenoid valve.
System Diagram
U.S.A. and CANADA
Except U.S.A. and CANADA
...