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Car Exhaust Manifold
Most vehicles are still powered by internal combustion engines usually with four six or eight cylinders. In creating the power to drive the vehicle the engine produces extremely hot exhaust gases, up to 1300 degrees Celcius from each cylinder. These gases flow from each cylinder exhaust into the manifold which is bolted to the engine's cylinder head.
The exhaust manifold, usually made of cast iron comprises several individual passage ways having one for each exhaust exhaust port. These individual passage ways merge into one, forming the outlet.
The engine pipe connects the exhaust system to the engine via the exhaust manifold. Exhaust gas temperature in the engine can reach over 1000 degrees Celcius when a vehicle is climbing or accelerating hard. Because of the high temperature of the engine pipe failure due to corrosion does not usually occur.
Cracks due to fatigue or reduced wall thickness and eventual perforation due to heat erosion are more likely causes of failure.
The catalytic converter converts harmful pollutants such as hydrocarbons, carbon monoxide and oxides of nitrogen contained in the exhaust gas into harmless emissions of nitrogen, carbon dioxide and water. A catalytic converter became a compulsory component in January 1986, when ADR 37 was implemented. The catalytic converter is usually located in the engine pipe in close proximity to the exhaust manifold.
Catalytic converters are designed to provide an extended service life. However correct operation of the converter relies on proper engine tuning the use of lead free fuel and the appropriate maintenance of the overall exhaust system. Because a vehicle's compliance with ADR 37 requires a catalytic converter to be fitted its removal will not only result in a heavy fine but also contribute to further damage of the planet's atmosphere.
How Catalytic Converters Work
The core of a catalytic converter is the monolith or substrate. Conversion of exhaust gases only begins after the substrate has reached an operating temperature of approx 200 degrees C. The optimum operating range is usually between 400 and 600 degrees C.
Depletion of precious metal begins at higher temperatures permanently degrading the performance of the catalysts. Temperatures of 1100 degrees C can melt the substrate causing total failure of the converterand causing severe restriction of the exhaust. This can be caused by engine faults and when engine management problems exist.
Catalytic converters also just wear out! Even a vehicle which has been regularly serviced and has no faults its converter could need replacing after 80 000 kilometres or after 5 years use.
The intermediate pipe sometimes called a connector pipe joins the front muffler to the rear muffler. It usually contains several complex bends to negotiate various undercar components. It is subjected to temperatures of up to 500 degrees Celcius. This area of the exhaust is prone to failure due to fatigue cracking and corrosion. Corrosion is more aggressive because lower temperatures in this part of the system do not evaporate the acidic condensation as rapidly.
The rear muffler is similar to the front muffler in function but has different internal construction. This produces the final exhaust note and ensures that noise emissions comply with government legislation in the form of ADR 28-01. The rear muffler can be positioned either in front or behind the rear suspension.
The tail pipe is an extremely important exhaust system component as it must ensure that the exhaust gas is emitted past the end of the vehicles body work preventing exhaust gas entering the luggage compartment and ultimately the vehicle's cabin. The current trend is to position the rear muffler toward the end of the traditional tail pipe behind the rear suspension. This not only saves space but also reduces exhaust noise more effectively across the range.