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/InstallationSwitch Panel Removal/Installation
1. Disconnect the negative battery cable..
2. Remove the car-navigation unit. (with car-navigation system).
3. Insert your hand from the lower side of the lower panel (without car-navigation
system) or the area where the car-navigation unit was installed (with car-navigation
system), press t ...
Service Publications
Service Publications
Factory-authorized Mazda service publications are available for owners who wish
to do some of their own maintenance and repair.
When requesting any of our publications through an Authorized Mazda Dealer, refer
to the chart below.
If they do not have what you need in stock ...
Front ABS Wheel Speed Sensor Removal/Installation
1. Remove the mudguard..
2. Remove in the order indicated in the table.
3. Install in the reverse order of removal.
4. After installation, verify that there is no twisting in the front ABS wheel-speed
sensor.
1
Connector
2
Bolt
...