To understand how the exhaust of a vehicle works, there must be a basic understanding of the engine as a whole.
The internal combustion engine in its simplest form is a large air pump. It gathers in air, mixes it with fuel, adds a spark and ignites the fuel and air mixture. The keyword here is ‘combustion’. Because the process that makes an internal combustion engine-powered vehicle move involves combustion, there are waste products, just as with any form of energy conversion. When a fire is lit in a fireplace, the waste products are smoke, soot, and ash.
For an internal combustion system, the waste products are gases, carbon particles, and tiny particles suspended in the gases, known collectively as exhaust. The exhaust system filters this waste and helps it to exit from the engine without discomfort to the vehicle occupants. A properly maintained exhaust system is essential to the clean and efficient operation of the car.
While modern exhaust systems are quite sophisticated, that wasn’t always the case. It wasn’t until the Clean Air Act of 1970 enacted in the United States of America that the government could mandate the amount and type of exhaust that a vehicle produced. The Clean Air Act was modified in 1976, and again in 1990, forcing automakers to produce vehicles that met a strict set of an emission standard. These laws contributed to the increase in the air quality of most major metropolitan areas in the United States and led to the exhaust system as we know it today.
Parts of the exhaust system
Exhaust valve: located in the cylinder head of an engine, and it opens after the combustion stroke of the piston to enable evacuation of the waste gases.
Piston: forces the gases created from combustion from the combustion chamber into the exhaust manifold.
Exhaust manifold: carries the emissions from the piston to the catalytic converter.
Catalytic converter: reduces the amount of toxin in the gases for cleaner emissions.
Exhaust pipe: carries the emissions from the catalytic converter to the muffler.
Muffler: reduces the noise produced from the combustion and expulsion of exhaust gases.
Essentially, the exhaust system works by collecting the waste from the combustion process, then moving it through a series of pipes to different parts of the exhaust system. The exhaust exits the opening created by the movement of the exhaust valve and is forced into the exhaust manifold. In the manifold, the exhaust from each of the cylinders is collected together and then forced into the catalytic converter. Within the catalytic converter, the exhaust is partially cleaned. Nitrogen oxides are broken into their respective pieces, nitrogen and oxygen, and oxygen is added to carbon monoxide, creating less toxic, but still dangerous carbon dioxide. Finally, the exhaust pipe carries the cleaner emissions into the muffler, which reduces the associated noises as the exhaust exits into the air.
Most common symptoms of a failing exhaust system
Exhaust system repairs are common. When there are so many moving parts in one system that works constantly, there are bound to be common repairs.
Cracked exhaust manifold: A vehicle can have a cracked exhaust manifold which will sound like a loud ticking sound from near the areas of the engine, which will sound like a giant clock.
Faulty doughtnut gasket: Will also be a loud ticking sound but can usually be heard coming from underneath the car when an occupant is sitting in the car with the door open.
Faulty O2 sensor: The check engine light on the instrument panel will illuminate
Excessively loud exhaust making hissing sounds: One of the first symptoms of a problem with the exhaust pipe is an excessively loud exhaust. If any of the exhaust pipes or tubes break or crack, they can cause an exhaust leak that will result in an excessively noisy engine. The exhaust may produce a hissing or tapping sound that may become more pronounced during acceleration.
The smell of raw gasoline from the exhaust: Another common symptom of a possible problem with the exhaust tubes is a noticeable exhaust smell. If any of the exhaust systems pipes or tubes become damaged and leak, the exhaust fumes may find their way into the cabin, giving off a smell of raw gasoline.
A decrease in power, acceleration, and fuel efficiency: Engine performance issues are another symptom of a potential problem with the exhaust tubes or pipes. If the pipes become damaged or corroded, they can sometimes produce an exhaust leak that can cause the vehicle to experience performance issues. An exhaust leak from a broken pipe can cause the vehicle to experience a decrease in power, acceleration, and fuel efficiency due to the loss of back pressure.
Hanging or dragging exhaust pipe: Another more serious symptom of a problem with an exhaust pipe or tube is hanging or dragging exhaust pipes. If any of the pipes break, they can sometimes hang or drag underneath the vehicle. The pipes may be visible from the sides of the vehicle or may make noise if they contact the ground.
Decreased fuel efficiency: When your power and acceleration decrease, often the fuel efficiency of your vehicle also decreases. To get your car to function in the same way that it does without an exhaust problem, it has to work even harder, therefore using more fuel. You may think that the cost of replacing or fixing your exhaust is high, but you’ll begin spending a lot more on petrol if you don’t get it fixed.
While exhaust systems are built specifically to withstand the high stress and heat conditions associated with engine exhaust, they are still prone to corrosion and rust over time. Usually, a problem with the exhaust system will be quite obvious. If not for the noise usually produced, for the effect on engine performance that usually occurs. If you suspect that your vehicle may be having an issue with an exhaust pipe or tube, have the vehicle inspected by a mechanic to determine what the vehicle needs.