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MLA Citation: Bloomfield, Louis A. "Automobiles" How Everything Works 18 Jul 2018. Page 1 of 3. 18 Jul 2018 <>.
190. How do certain mufflers provide more horsepower?
A muffler's job is to control the flow of exhaust from the cylinders to the outside air, so that the abrupt fluctuations in pressure created by the opening cylinders are smoothed away by the time the exhaust leaves the car's tail pipe. The pressure fluctuations create sound and, by smoothing them away, the muffler quiets the engine. But the easiest ways to smooth away the pressure fluctuations also impede the flow of exhaust from the cylinders. The result is that some exhaust is trapped in the cylinders and interferes with the operation of the engine. The car's gas mileage drops. A good muffler smoothes out exhaust pressure without impeding its flow and without reducing gas mileage.

191. How does a nitrous kit on a car make it go faster?
According to David Ingham, a nitrous kit is a system that injects nitrous oxide into the air intake. This technique was developed during WWII as a way to obtain short bursts of extra power from gasoline engines. Keith Spillman points out that the nitrous oxide is injected as a dense liquid so that it greatly increases the number of oxygen atoms inside the cylinder at the moment the fuel ignites. Since nitrous oxide breaks down into nitrogen and oxygen at high temperatures, it supports combustion and allows more fuel to burn during each engine cycle. The engine thus produces more power. The liquid nitrous oxide also provides an "intercooling" effect when it evaporates—it cools the gases in the cylinder prior to compression so that there is less possibility of knocking.

192. How does using better spark plugs make your car run more efficiently? Is it worth paying extra for those spark plugs? Would it improve your car's performance?
According to several readers of this web site, there is a difference between standard and high performance spark plugs. The high performance spark plugs produce a more intense spark and ignite the fuel and air mixture more reliably than standard plugs. That would indicate that igniting the fuel and air mixture at just the right moment isn't as straightforward as it seems. If the plugs don't fire reliably and don't light the gasoline at exactly the right moment every single time the cylinder is supposed to fire, the car's efficiency will suffer.

193. In modern car alarm systems, people can start the engine with a push of a button from a remote. How is this done?
This question has a long answer, because there's lots going on. First, there is a radio transmission from the key chain to the car when you push the button. That transmission is carefully encoded so that no one else can trigger your car (the car's receiver checks for the proper authorization code when it receives the radio transmission). I won't describe the transmission/reception process in detail, because that's a whole story in its self. The receiver than activates the car's electric system, which was cut off when the driver last turned off the car. The electric system is now ready to provide sparks at the proper moments when the engine turns. Finally, the receiver starts the engine turning by activating the starter motor. An electromagnetic solenoid (a coil of wire with a piece of iron inside) pushes the starter motor or a gear from the starter motor against the car's flywheel (a huge gear attached to the engine's crankshaft) and power is supplied to the starter motor. The motor begins turning and it turns the engine. The electric system provides sparks and the engine starts up.

194. I've heard about a car (I think some type of Ferrari) that has a clutch-less manual transmission.
According to Bryan Tiedemann, Ferarri makes a computer-shifted manual transmission. It begins with a standard manual transmission (gears, input/output shafts, synchronizers) that's similar to that of many "stick-shift" cars of today. However, instead of having a driver-controlled clutch and shift lever, a computer regulates the actual mechanical clutch movement and it also shifts gears via servos and motors. The driver uses a "shift paddle" on the steering wheel to shift, and the computer does the actual shifting. The automatically controlled manual is better than a normal automatic because manual transmissions give better performance than automatics and no energy is lost as heat in hydraulic couplings.

195. I've heard of people using moonshine as fuel for cars and pick up trucks. Is that possible and, if it is, how well does it work?
Yes, it's probably possible. Moonshine (and any distilled spirits) is a mixture of ethanol (ethyl alcohol) and water. Depending on how picky you are during the distilling process, the water content may be as low as 10% (you can't do better by distilling because 4.4% water and 95.6% ethanol form an azeotrope—a low boiling point mixture blend that can't be separated by distilling). Ethanol burns nicely and should make a pretty good fuel. Obviously, the less water the better, because water doesn't burn and may impede the combustion of ethanol. Ethanol is often included in gasoline to reduce exhaust emissions, but only at about the 10% level. Unfortunately, ethanol is also more corrosive than normal gasoline, so people worry about it damaging their engines.

196. What is the purpose of pistons in an engine?
The piston moves in an out of a cylinder, moving the air, fuel, and exhaust about and extracting work from the burned fuel and air. Without the piston, there would be no way to obtain energy from the gasoline.

197. What's the difference with a Mazda rotary engine?
The rotary engine was supposed to revolutionize automobiles when it was first introduced several decades ago. Instead of a piston and cylinder, it has a triangular shaped object that wobbles around the inside of a hollow chamber. This object traps a fuel and air mixture, compresses it, ignites it, extracts energy from it, and releases it into the outside air, just as a normal engine does. But it uses the wobbling motion of the triangle, rather than the reciprocating motion of the piston and cylinder. The rotary engine has fewer moving parts to wear out, but it evidently has other issues that have prevented its wide adoption.

198. Why do I need a choke?
When an engine is cold, it runs better with a rich mixture (more fuel, less air). Years ago, the choke pinched off the airflow to the cylinder (hence the name "choke") and was operated manually. Later it was operated automatically (often turning off too soon and causing the car to stall a few minutes after starting). In modern cars, there is no choke, just the computer controlling the fuel and air mixture on a moment-by-moment basis.

199. Why is it good to put premium gas in your car during the winter? If premium gas does not burn easily, does it also not freeze easily?
I'm not sure that it is better to put premium gas in your car during the winter. If you car operates properly on regular during the summer, then it should also operate properly on regular during the winter. Actually, summer gasoline and winter gasoline are slightly different. When it's cold outside, gasoline doesn't evaporate as easily so it needs to be reformulated to make it more volatile. During the winter, the gasoline manufacturers add more small molecules to the mixture so that it turns into a gas more easily. But they try to retain the same resistance to ignition in each of their gasoline grades. In any case, gasoline doesn't freeze at normal temperatures, so that's not a problem. Only water that condenses in your gas tank will freeze and can plug your gas line.
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