This week we're sharing the final essay in our Essay Rock Star semester long program by Devin Hoch, one of our high school students. The essay below is an expository essay, an essay whose purpose is to explain or describe a chosen subject. Devin challenged himself with a very complicated process to explain for his final essay project, as you'll see below. We're sorry to see him go!
Air Intake and Exhaust Systems in Vehicular Engines
Air is a very important and essential component in running an engine. Air is used in all types of engines except rocket engines. However, we will be discussing common gas and diesel engines in this essay.
First I will do a general overview of how a gasoline engine works and primarily how the air is used. Initially, the air is filtered at the beginning of the process. Then, in the carburetor it is combined with gasoline and injected into the main cylinder of the engine, where the power is produced. In the cylinder it is compressed and ignited to make a small explosion. This explosion moves the piston which, in turn, powers the crankshaft, which turns the wheels. Though this process sounds very complicated...it is, in fact, very complicated. There is no easy way to describe the workings of a gas engine but I will try my best, working from the air intake at the beginning to the exhaust at the end.
At the very beginning of the process, the air is pulled through a filter by the vacuum produced by the engine. Filtration is a very essential part of the air intake process because if dirt or debris was sucked into the engine internal damage to the engine would most likely be the result. I will stop here to explain something: the higher your air flow through the engine, the more horsepower and speed will be produced. Higher air flow is available through all sorts of upgrades, high performance air filters being one of them. These air filters simply take the air and filter it using an easier route for the air.
Another upgrade which will boost your horsepower output to a ridiculously high level is a turbocharger. This is a contraption that is installed on the air intake tube between the filter and where the air enters the engine. How this machine works is by using hot exhaust gases to power a turbine which preheats and pressurizes the cold air which was just filtered. The turbo then injects the heated, pressurized air into the carburetor. This almost completely takes over the work the engine would have had to do to pull in air.
Now we return to the air system. I just mentioned the carburetor. But what is a carburetor? The carburetor, or carb, is where the air and fuel are combined. This is where the throttle valve is located. When you press the gas pedal you are opening the throttle valve, allowing more fuel to be combined with the air. This produces more power.
There is another booster which I must include. This would be nitrous oxide or alcohol injection. This is used only in cars used for drag racing as it would be very dangerous to use on the street, not to mention illegal. These boosters increase acceleration to a extremely high level. But how does it work? There is a small tank, usually located in the trunk of the vehicle, containing nitrogen. This is injected into the engine, causing a chemical reaction dramatically increasing the amount of fuel consumed. This increases the speed and performance of literally everything involved.
Before I got sidetracked on boosters, I was explaining how the carb works. After the air and fuel are combined they are injected into one of the cylinders. There are all different sizes and types of engines. All American vehicles have a vee engine. Have you ever heard of a "V8" engine? This simply means that it is a vee engine with eight cylinders. This is a relatively large engine. There are engines with as few as three cylinders all the way up to sixteen! Motorcycle engines usually have one or two.
Picture a bike tire pump. This is similar to how the inside of an engine cylinder works. When you pull up on the handle you suck air in and when you push the handle down you pressurize the air. Then at the point after the air and fuel are pressurized, the spark plug explodes the mixture, creating power. That is when the car really takes off!
Now for the final phase of air usage. This is the exhaust phase. Just how air enters the cylinder, there is also an "out" valve for the exhaust gases. This gas flows through the exhaust pipe until it reaches the muffler. The muffler silences the sound of the rapid explosions in the engine. If you've ever heard a small airplane fly over, you can picture what our cars would sound like with no muffler. With no muffler, the airplane pilot and passengers must wear noise-blocking headsets to hear each other talk! With modern mufflers, our cars are almost silent.
The inside of the muffler is padded and the exhaust gases are filtered to prevent pollution and reduce noise. Once again, similar to the intake filter, the higher air flow the better. Have you ever seen a diesel truck blow black smoke out of it's exhaust? This is usually because the exhaust filter was removed to produce higher air flow. This produces more horsepower and cuts down on bad fuel mileage.
An engine is a very complex machine. There are a myriad of ways to increase the power produced by said engine. Air is one of them and one of the most important, I daresay. We have reviewed much information concerning air intake and exhaust systems. Some of it is relevant to street cars and some exclusive to racing cars. I believe we have covered all of the many phases of air usage in a vehicle engine from filtration to exhaust. So, in conclusion: got bad gas mileage? Not enough horsepower output? Want your vehicle to sound awesome? Upgrade your air system!
by Devin Hoch