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5 November 2008
More Than a Simple Pipe
The Exhaust System
A potential source of noise, pollution, and, at times, even harmful emissions that can be a health hazard, this system can also hinder engine performance if a routine check is not duly performed.
 Aside from the usual main components such as the exhaust manifold, front, middle, and back hoses, catalytic converter, muffler, clamps, and joints, the exhaust system has accumulated other important accessories over time to better manage the engine’s performance and reduce toxic waste released into the atmosphere.
The oxygen sensor
This sensor’s purpose is to detect the presence of oxygen in the exhaust gas. We mainly use zirconia sensors, which emit a tension signal that varies according to the oxygen content, and titanium sensors, whose resistance fluctuates in the same way. In order to produce a useful signal, these two types of sensors must reach an accurate operating temperature.
New sensors
With the advent of OBD-II on-board diagnostic systems as of 1996, manufacturers added various oxygen sensors in order to better control exhaust pollutant emissions by improving powerplant management. Their position varies as per their application. The sensor nearer the engine essentially allows the command module to adequately dose the air-fuel mix, and the ones located on either side of the catalytic converter see to its efficiency.
Life and efficiency
With time, O2 sensors lose sensitivity and precision, which slows the ECM response following changes in oxygen content, and consequently the air-fuel mix ratio. Moreover, they may be contaminated by carbon or oil deposits. When this happens, the “Check Engine” light may turn on, showing that the sensor is defective. The scanner will allow you to detect the pertinent error code.
The EGR valve
Triggered by a vacuum-pressured electrovalve controlled by the ECM, the exhaust gas recycling valve serves to lower the combustion in order to curb NOx production. Upon deceleration, the valve opens to allow admission of exhaust gas into the intake manifold. As for the O2 sensors, they can jam and send a malfunction signal to the module.
The catalytic converter
As its name indicates, its function is to convert burned gases into ecological zero-emission components. Depending on one of the three types found on the market, they may contain platinum, palladium, and sometimes rhodium. When exhaust gases come into contact with one of these components, a chemical reaction occurs, transforming the carbon monoxides, nitrogen oxides, and hydrocarbons into harmless by-products.
Investigating malfunctions
The proper operation of the three abovementioned components could be hindered by oil or carbon deposits, an improper mixture of air-fuel, and dirty or used spark plugs bringing on an incomplete combustion. Using a vacuum gauge or pyrometer to measure operating temperatures will help you pinpoint the source of any malfunction. More than a simple pipe, isn’t it? | |
