Exhaust System: Description and Operation

Exhaust System

5.0L V8 COMPONENT LOCATION - FROM 2010MY









EXHAUST SYSTEM
The 5.0L V8 stainless steel exhaust system is supplied from the factory as a one-piece assembly and is connected to the engine with two exhaust manifolds. It is attached to the underside of the body with six rubber mountings.
The system comprises 2 stub pipes which are used to connect the system to the exhaust manifold. The stub pipes connect to the system with 3 studs and locknut. A gasket seals the joint between the stub pipe and the system.
A catalytic converter is welded into each down pipe in the system and comprises a starter catalyst and a main catalyst. An intermediate pipe is welded to the opposite end of each catalytic converter and connect into welded joints with the 2 centre silencers. Each centre silencer has a capacity of 5 liters. Three baffle plates inside the silencer are connected by tubes with the rear most tube being perforated. The two compartments between the two rear most baffle plates are packed with steel wool and glass fibre packing to absorb combustion noise as the exhaust gasses pass through the silencer.
A connecting pipe is welded between each centre silencer and the rear silencer assembly. Internally the rear silencer assembly is divided into two independent silencers each with its own tailpipe. The tailpipes on the naturally aspirated derivative are curved downwards and not visible from the rear of the vehicle. The tail pipes on supercharger vehicles are straight and fitted with a stainless steel finisher.
The rear silencer is divided into 2 separate compartments, although the centre baffle plate which divides them has a perforated section to allow gasses to pass from one side to the other. Each compartment has 2 baffle plates connected by an inlet tube. The inlet tube allows gasses to pass into the centre compartment through a perforated section and the remaining gasses are passed into the outer compartment. The outer compartment is packed with steel wool and glass fibre to further absorb combustion noise as exhaust gasses pass between the baffle plate and exit through the tail pipe.
Although supplied from the factory as a one-piece, welded assembly, in service sections of the system can be replaced individually. Service joints are identified by indentations on the pipes, to show where the exhaust pipes can be cut to accommodate the replacement service sections.
After the replacement sections are positioned, the system integrity is restored by sealing the service joints with one piece repair sleeves.

EXHAUST MANIFOLDS
The fabricated stainless steel twin skin exhaust manifolds are unique for each cylinder bank. Spacers on the securing bolts allow the manifolds to expand and retract with changes of temperature while maintaining the clamping loads. Heat shields are integrated into the exhaust manifold gaskets. Each manifold has a threaded port near to its outlet which allows for the fitment of the pre-catalyst HO2S.

CATALYTIC CONVERTERS
The engine management system provides accurately metered quantities of fuel to the combustion chambers to ensure the most efficient use of fuel and to minimize the exhaust emissions. A threaded boss is located on each manifold and a and another threaded boss is located between the starter and the main catalyst to house the pre and post catalyst oxygen sensors. The engine management system monitors the sensors and uses the information to further improve the fuelling and exhaust emissions.
To further reduce the carbon monoxide and hydrocarbons content of the exhaust gases, two catalytic converters are integrated into the front down pipe from each exhaust manifold. In the catalytic converter the exhaust gases are passed through honeycombed ceramic elements coated with a special surface treatment called 'washcoat'. The washcoat increases the surface area of the ceramic elements by a factor of approximately 7000. On top of the washcoat is a coating containing metals, which are the active constituent for converting harmful emissions into inert by-products. The metals add oxygen to the carbon monoxide and the hydrocarbons in the exhaust gases, to convert them into carbon dioxide and water respectively.
Two catalytic converters are used in each cylinder bank down pipe. A starter and main catalyst are located below the downpipe flange. The starter catalyst is monitored by two HO2S (heated oxygen sensor)'s. The main catalyst is not monitored.