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About Car Exhaust Systems
We sell more than 150,000 pieces of complete exhausts per year in UK, Greece, Cyprus and Malta. From down pipes, front pipes, middle and rear silencers for European and Japanese cars.
The exhaust system is designed to direct gases produced by combustion out of the engine. By ensuring a continuous, smooth flow of exhaust gases out of the engine, the exhaust system improves engine performance. During the design process account has to be taken so that inside the silencer the perforated tubes and buffers create chambers that produce the variables in flow turbulence in pressure and temperature that will reduce noise and drive exhausts gasses out fast enough so that back pressure is reduced to the minimum. The volumes, the diameter of tubes, the diameter of holes, the thickness of materials, the smoothness of the pipe bends, all together change the outcome, that is why an exhaust system requires fine adjustment.
Sound is a pressure wave formed from pulses of alternating high and low air pressure. These pulses make their way through the air at 1,236 kilometers per hour (Speed of sound). These pulses are generated when an exhaust valve opens after the explosion in the cylinder and gasses at high temp (up to 1,300°C.) and high pressure enter the manifold. At 5,000 rpm a four cylinder engine will open the exhaust valves of a single cylinder 21 times in one second, and a 12 cylinder Ferrari will open the exhaust valves of a single cylinder 63 times in a second.
The gasses pass through the manifold and then enter the down pipes that carry them to another component in the system which is the catalytic converter. These gasses are mainly Carbon Monoxide CO, a poisonous gas, Nitrogen oxides (NOx) and Hydrocarbons which are converted by the Catalyst into carbon dioxide and water vapor. The CAT can do this in a chemical reaction within it's substrate.
The chemical processes within the catalytic converter do not start until a temperature of 300°C to 350°C is reached. The lambda sensor measures continuously the oxygen content of the exhaust gas and provides this information as a control parameter to the ECU which in turn controls electronically the mixture of fuel to air ratio.
Front Silencer & Rear Silencer
The gasses enter the front silencer at 800 to 1,000 °C and until they reach the final silencer the temperature goes down to 350 °C.
As a result, the rear silencer is subject to extremely high corrosion due to an increased rate of exhaust gas condensation and a lower rate of evaporation.
If the vehicle is continually driven over short distances or in stop-and-go conditions, the rate of corrosion will accelerate as the exhaust system is unable to reach condensation evaporation temperature. This is a key factor in premature corrosion-induced failure.