Exhaust System: Overview Chrysler Pacifica CS

DESCRIPTION

The exhaust system consists of a catalytic converter, muffler, and a resonator with connecting pipes in-between. The system is serviced in three sections; the catalytic converter, the muffler, and the resonator and tailpipe. (Scheme 4) A torca clamp is used to connect the joint between the muffler and catalytic converter. A torca clamp is used to connect the muffler and the resonator and tailpipe. Support hanger rods with rubber isolators are used to support and isolate the exhaust system. A flexible joint, integral to the catalytic converter, allows for engine movement. A second flexible joint is located between the muffler and the resonator/tailpipe assemble to allow for exhaust system movement. The exhaust system is tuned for each vehicle/powertrain combination.

Scheme 4

Exhaust system restriction can be checked by measuring back pressure using the DRB III® and PEP module pressure tester.

1. Disconnect and remove the upstream (before catalytic converter) oxygen sensor.
2. Install the Exhaust Back Pressure Fitting Adaptor CH8519.
3. Connect the Low Pressure Sensor (15 psi) CH7063 to the back pressure fitting.
4. Following the PEP module instruction manual, connect all required cables to the DRB III® and PEP module. Select the available menu options on the DRBIII® display screen for using the digital pressure gauge function.
5. Apply the park brake and start the engine.
6. With transmission in Park or Neutral, raise engine speed to 2000 RPM. Monitor the pressure readings on the DRBIII®. Back pressure should not exceed specified limit. Refer to specification in table below. See EXHAUST BACK PRESSURE LIMITS . NOTE: For applications with dual catalytic converters, repeat test on opposite converter using the previous steps.
7. If pressure exceeds maximum limits, inspect exhaust system for restricted component. Replace component(s) as necessary.

EXHAUST BACK PRESSURE LIMITS

It is easier to service the exhaust system components. (Scheme 4)when system is removed from the vehicle.

Scheme 5

1. Raise vehicle on hoist.
2. Disconnect the two oxygen sensor connectors.
3. Remove the nuts at the exhaust manifold.
4. Support exhaust system with jack stand.
5. Remove the rubber isolators from the support brackets. (Scheme 5) 1 - SUPPORT BRACKET 2 - ISOLATOR 3 - RESONATOR/PIPE
6. Lower exhaust system and lay on the ground.

Note. Care must be taken not to scratch the black paint on the rear of the muffler. (Scheme 5)

Note. When replacement is required on any component of the exhaust system, it is most important that original equipment parts be used for the following reasons

1. To ensure proper alignment with other parts in the system.
2. Provide acceptable exhaust noise levels and does not change exhaust system back pressure that could affect emissions and performance.

1. Install and loose assemble the front resonator to the converter pipes.
2. Place the exhaust system on two supports (one on side of muffler, one behind the resonator). Connect the system to the exhaust manifold. Do not tighten the nuts.
3. Install the system's rubber isolators onto the support brackets. (Scheme 5)
4. Visually inspect the isolators. They should be straight when viewing from front to back of the vehicle. Working from the front of system, align each component to maintain position and proper clearance with underbody parts.
5. Tighten the catalytic converter-to-exhaust manifold nuts to 37 N.m (325 in. lbs.) and torca clamp to 54 N.m (459 in. lbs.).
6. Lower the vehicle.
7. Start the engine and inspect for exhaust leaks. Repair exhaust leaks as necessary.
8. Check the exhaust system for contact with the body panels. Make the necessary adjustments, if needed.

The toe board three-way catalytic converter is connected to the exhaust manifold by the use of a down pipe assembly. The outlet connects to the muffler inlet pipe and is secured with a torca clamp. (Scheme 6)

Scheme 6

OPERATION

The three-way catalytic converter simultaneously converts three exhaust emissions into harmless gases. Specifically, HC and CO emissions are converted into water (H2O) and carbon dioxide (CO2). Oxides of Nitrogen (NOx) are converted into elemental Nitrogen (N) and water. The three-way catalyst is most efficient in converting HC, CO and NOx at the stoichiometric air fuel ratio of 14.7:1.

The oxygen content in a catalyst is important for efficient conversion of exhaust gases. When a high oxygen content (lean) air/fuel ratio is present for an extended period, oxygen content in a catalyst can reach a maximum. When a rich air/fuel ratio is present for an extended period, the oxygen content in the catalyst can become totally depleted. When this occurs, the catalyst fails to convert the gases. This is known as catalyst "punch through."

Catalyst operation is dependent on its ability to store and release the oxygen needed to complete the emissions-reducing chemical reactions. As a catalyst deteriorates, its ability to store oxygen is reduced. Since the catalyst's ability to store oxygen is somewhat related to proper operation, oxygen storage can be used as an indicator of catalyst performance. Refer to the appropriate Diagnostic Information for diagnosis of a catalyst related Diagnostic Trouble Code (DTC).

The combustion reaction caused by the catalyst releases additional heat in the exhaust system, causing temperature increases in the area of the reactor under severe operating conditions. Such conditions can exist when the engine misfires or otherwise does not operate at peak efficiency. Do not remove spark plug wires from plugs or by any other means short out cylinders, if exhaust system is equipped with a catalytic converter. Failure of the catalytic converter can occur due to temperature increases caused by unburned fuel passing through the converter. This deterioration of the catalyst core can result in excessively high emission levels, noise complaints, and exhaust restrictions.

Unleaded gasoline must be used to avoid ruining the catalyst core. Do not allow engine to operate above 1200 RPM in neutral for extended periods over 5 minutes. This condition may result in excessive exhaust system/floor pan temperatures because of no air movement under the vehicle.

The flex joint allows flexing as the engine moves, preventing breakage that could occur from the back-and-forth motion of a transverse mounted engine.

The exhaust system heat shields. (Scheme 7) (Scheme 8), or (Scheme 9) are attached to the under body of the vehicle.

Scheme 7

Scheme 8

Scheme 9