Exhaust gas gas is undesirable, noxious, or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (properly indicated as CH, but typically shown simply as "HC" on emissions-test slips) from unburnt fuel, nitrogen oxides (NO) from excessive combustion temperatures, and particulate matter (mostly soot). Exhaust gas temperature (EGT) is important to the functioning of the catalytic converter of an internal combustion engine. It may be measured by an exhaust gas temperature gauge. EGT is also a measure of engine health in gas-turbine engines (see below). During the first two minutes after starting the engine of a car that has not
Aftermarket exhaust parts but are very effective at reducing the sound levels. The piping that connects all of the individual components of the exhaust system is called the exhaust pipe. Contrary to popular belief, the larger diameter exhaust pipe is not always better. If the pipe is too large, the scavenging effect will suffer at low rpm, resulting in loss of torque and driveability. Running a pipe that is too large may also decrease a car's ground clearance, increasing the risk of the exhaust being damaged when the car moves over an uneven surface. While it was common for the stock or factory