Exhaust repairs don't have to be exhausting - Simple approaches can keep exhaust system work rolling - Motor Age - Automotive training, certification & parts info
Exhaust manifold flange studs go through a lot of temperature inversions and can be hard to remove.
Remember back when you were just a kid and you told your mom you were going to hold your breath until you got your way? I'm
sure that didn't work out too well for you, because she knew that whatever air you took in would eventually have to come back
out. You really didn't have a choice in the matter.
Catalytic converters can come in assemblies with pipes and flanges attached.
Imagine, though, if you were a runner and you could breathe in fine but it was extremely hard to exhale. I don't think you
would be a very efficient runner. The same thing holds true for our vehicles and the way they exhale — their exhaust system.
Exhaust Flow at a Glance
For an engine to be efficient, it must have the proper exhaust flow to get rid of all the products of the combustion process.
The air that is taken in through the intake has to be expelled after being used and there's only one way out: the exhaust
system.
(Top LEFT) A fat cat. (Top right) Flex joints are used in some systems to accommodate engine and exhaust system movement.
(Bottom LEFT) Heat shields and tight locations can be the source of rattles and vibrations. (Bottom right) Low back pressure
mufflers will usually have resonators in the system.
The exhaust flow actually starts in the combustion chamber where the fuel/air mixture is burned. After that it becomes a byproduct
of the combustion process and has to leave the engine via the exhaust valves in the cylinder head and then out through the
exhaust manifold or header pipe, depending on engine design. While exhaust systems vary based on engine design, manufacturer,
environmental standards or even size constraints, they all follow some basic design characteristics.
After leaving the engine, there's the required catalyst that can be a close-coupled converter or a catalytic converter in
the exhaust pipe itself. A close-coupled converter actually can be a part of the exhaust manifold and is used to allow for
rapid heat up, which aids in a quicker cleanup of the exhaust gasses.
Some systems may have an exhaust resonator just pass the converter to aid in the reduction of exhaust harmonics that might
cause unwanted noises or vibrations. Exhaust pipes then route the flow underneath the vehicle and into the muffler. Here,
of course, is where most of the exhaust noise is eliminated. This is done by the use of various chambers and dampening material
used within the muffler itself.
Finally, we reach the termination point at the tailpipe or exhaust tip, depending on system design. By this time the exhaust
has been cleaned up and quieted down to acceptable levels. Based on engine size and design, this is done through either a
single or dual exhaust system.
Randy Wilson is an ASE Master Certified Technician and a factory trained GM Certified Technician. He has more than 20 years of experience and does drivability and electrical diagnosis at Solomon Chevrolet Cadillac in Dothan, Ala.
Articles by Randy Wilson
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