By P Sanchez
The tailpipe. For a lot of people, it’s the part of the car that is both mundane as it is a patent indication of the nature of the machine. More accurately, the tailpipe is the most visible part of an important sub-system of an automobile: the exhaust system.
At its most basic, the job of the exhaust system is to safely route the exhaust gases out of the engine and away from the vehicle. After the engine makes useful mechanical work from the combustion of fuel and air, the spent gases need to be vacated from the cylinders which have to be ready for the next charge of fuel-air mix. Thus the gases are released into the exhaust manifold, go through connecting metal tubes and out the back through the tailpipe.
It sounds simple enough but the exhaust system actually serves other functions than just plumbing for waste gas. Much like the rest of the modern car, the exhaust system is a product of decades of purposeful design.
Huffin' and Puffin' (A Little History)
Anytime you burn fuel in an enclosed chamber, whether it’s firewood in a furnace, coal in the firebox of a locomotive, or gasoline in an internal combustion engine, burnt gas and fumes need to be expelled as soon as possible. Ideally, directly venting out the burnt gas to the outside air is the most efficient way. However it’s not always the most favorable.
Without chimneys to give an escape for gases, fumes from the fireplace will quickly fill a house and asphyxiate the residents; it’s not the kind of reprieve people expect for spending cold winters indoors. Comparatively, steam locomotives have their characteristic flutes to shoot smoke and scalding steam safely overhead, which kept the train engineer, working hands, and passengers’ travelling condition more comfortable. Also, avoiding all that soot surely helped in keeping black lung disease at bay.
Steam power designs paved the way to the internal combustion engine. The newer technology was lighter, operated reliably, and had better power-to-weight ratio, making it a suitable power plant for new concept in road transportation: the horseless carriages (or cars, for short). Owing to the internal combustion engine’s compact nature, subsequent car designs managed to tuck away the unsightly engine in a large wooden or metal chest (called “trunk”). Sealing off the engine from the outside meant that exhaust gases had to be piped out of the engine’s enclosure, and as such the ancestor of the modern exhaust system was born.
One of the earliest secondary functions added to the exhaust system is the exhaust whistle. It’s a throwback from steam locomotive’s whistle that give them the characteristic “choo-choo” sound to alert bystanders on the road and other oncoming vehicles. The exhaust whistle is attached at some point along the exhaust pipe, and similarly to trains, takes some of the exhaust gases to sound-off. Only later when the more consistent, simpler to produce, and easily controllable electric car horn was introduced that the exhaust whistle would fall out of favor.
Next time, we’ll talk about another secondary function of the exhaust system that was also invented at the dawn of the automobile; a feature that has remained to this day a standard in the design of the exhaust system for any modern day car: the muffler.