Description

Exhaust System

CATALYTIC CONVERTERS
In the catalytic converters, 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 palladium and rhodium, which are the active constituents for converting harmful emissions into inert by-products. The palladium and rhodium add oxygen to the carbon monoxide and the hydrocarbons in the exhaust gases, to convert them into carbon dioxide and water respectively.

SEMI-ACTIVE MUFFLER VALVE (5.0L SUPERCHARGER VEHICLES ONLY)
The semi-active muffler valve is operated by the pressure in the exhaust system. At low engine speeds the valve head is closed or partially closed to provide a more refined noise quality. At higher engine speeds the increased pressure within the exhaust system opens the valve head to provide a more sporting noise. This is achieved by the valve, which once open, allows the exhaust gasses to by-pass the baffle tubes and plates in the rear silencer.

FRONT SECTION - 4.2L NATURALLY ASPIRATED (NAS ONLY) - From 2010MY
The front section comprises two separate pipes, each incorporating a catalytic converter. Each catalytic converter has a welded inlet pipe with a flange. The inlet pipe is flared into a cone which mates with the exhaust manifold. The flange has two holes which locate on studs in the exhaust manifold and is secured with flanged nuts. Each catalytic converter is fitted with a pre and post catalyst HO2S (heated oxygen sensor).
Each catalytic converter has a curved outlet pipe which mates with the respective inlet pipe for the applicable resonator on the center section. The joint on each pipe is secured with a clamp.

FRONT SECTION - 5.0L NATURALLY ASPIRATED AND SUPERCHARGER - From 2010MY
The front section is common to both the naturally aspirated and supercharger vehicles. The front section comprises two separate pipes each incorporating a catalytic converter. Each catalytic converter has a welded pipe with a flange, which is flared into a cone which mates with the exhaust manifold. Each flange has two holes which locate on studs in the exhaust manifold and are secured with nuts. Each catalytic converter is fitted with a mid brick catalyst HO2S (heated oxygen sensor). The mid brick catalyst HO2S (heated oxygen sensor) is located in the exhaust manifold.
A curved pipe from each catalytic converter locates into the resonator inlet pipes of the center section. The LH (left-hand) pipe is fitted with a mass damper which absorbs resonance from the system.

REAR SECTION - 4.2L NATURALLY ASPIRATED (NAS ONLY) - From 2010MY
The 2 inlet pipes each connect into a separate resonator silencer. Each resonator silencer is cylindrical in shape and houses 2 perforated tubes separated by 2 baffle plates. Exhaust gasses exit each resonator silencer via an outlet pipe. The 2 outlet pipes are joined together behind the resonators with a cross over pipe. Each pipe also has a welded hanger bracket which allow the rear section to be supported on mounting rubbers. A further bracket is welded to each pipe which braces the 2 pipes together.
The 2 rear silencers each have a welded inlet pipe which mate with the outlet pipes from the resonator silencers and are each secured with a clamp. The inlet pipes each have a welded hanger bracket which support each rear silencer at the rear of the vehicle on mounting rubbers. The fabricated rear silencers have 2 perforated tubes which are supported on 2 perforated baffle plates. The exhaust gasses are expelled from the rear silencer via a single outlet pipe. The outlet pipe from each silencer has a welded hanger bar which support the rear silencer on mounting rubbers. The outlet pipe is fitted with a welded outlet which is covered with a polished stainless steel finisher which is part welded to the silencer.

REAR SECTION - 5.0L NATURALLY ASPIRATED - From 2010MY
The 2 pipes from the front section each connect into 2 short pipes on the center resonator box and are secured with clamps. Two pipes from the resonator box split the system into 2 sections which each connect into another resonator. Each resonator silencer houses perforated tubes separated by baffle plates. Exhaust gasses exit each resonator silencer via an outlet pipe. The 2 outlet pipes are joined together behind the resonators with a cross over pipe. Each pipe also has a welded hanger bracket which allow the rear section to be supported on mounting rubbers. A further bracket is welded to each pipe which braces the 2 pipes together.
The 2 rear silencers each have a welded inlet pipe which mate with the outlet pipes from the cylindrical resonator silencers and are each secured with a clamp. The inlet pipes each have a welded hanger bracket which support each rear silencer at the rear of the vehicle on mounting rubbers. The fabricated rear silencers have 2 perforated tubes which are supported on 2 perforated baffle plates. The exhaust gasses are expelled from the rear silencer via a single outlet pipe. The outlet pipe from each silencer has a welded hanger bar which support the rear silencer on mounting rubbers. The outlet pipe is fitted with a welded outlet which is covered with a polished stainless steel finisher which is part welded to the silencer.

REAR SECTION - 5.0L SUPERCHARGER - From 2010MY
The 2 pipes from the front section each connect into 2 short pipes on the center resonator box and are secured with clamps. Two pipes from the center resonator box each connect into a second resonator silencer. The resonator silencer comprises perforated tubes separated by 2 baffle plates. Exhaust gasses exit the resonator silencer via 2 outlet pipes. Each pipe has a welded hanger bracket which allows the rear section to be supported on mounting rubbers. A further bracket is welded to each pipe which braces the 2 pipes together.
The 2 rear silencers each have a welded inlet pipe which mate with the outlet pipes from the cylindrical resonator silencers and are each secured with a clamp. The inlet pipes each have a welded hanger bracket which support each rear silencer at the rear of the vehicle on mounting rubbers. The fabricated rear silencers have a perforated inlet tube which is supported on 2 baffle plates. Each rear silencer has a welded hanger bar which supports the rear silencer on mounting rubbers. The outlet pipe is fitted with a welded twin outlet which is covered with 2 polished stainless steel finishers which are part welded to the silencer.

Semi-Active Muffler Valve

NOTE:
LH (left-hand) silencer shown, RH (right-hand) silencer similar









A semi-active muffler valve is located in the rear of each rear silencer. The valve comprises a valve head, a valve shaft, a shaft guide, a housing shell, a membrane and a spring. The valve head is connected to the membrane by the valve shaft which is located within the shaft guide. The valve shaft is attached to the membrane with a pin. The membrane is located inside the housing shell and is held in position by the spring.
The valve head is located in and seals against the over pipe. When the exhaust gas pressure increases and overcomes the spring pressure, the valve head is lifted and the gasses by-pass the valve and are expelled though slots in the valve cage into the rear chamber and into the outlet pipe.
When the semi-active muffler valve is closed the exhaust gasses are expelled from the inlet tube through the perforations. The exhaust gasses then pass through perforations in the outlet pipe and are expelled from the silencer via the single outlet pipe and 2 polished stainless steel finishers.
When the semi-active muffler valve is open, the exhaust gasses are released into the rear chamber. The exhaust gasses then pass directly into the open end of the outlet pipe and are expelled from the silencer via the outlet pipe and the 2 polished stainless steel finishers. With the valve open, the gasses reduce through the baffle plates and tube perforations giving the exhaust note a more 'sporty' sound.