Welcome to You Ask Andy

 

Jon Anton Auer, age 10, of Wichita, Kansas, for his questions

How does gasoline make a car run?

The motor of an automobile is called an internal combustion engine. In simple words, internal means inside. Combustion means burning, or fire. Internal combustion means that the burning vehicle takes the auto go happens right inside the engine. The combustion is a special kind of burning. It is a lot of little explosions ‑ very carefully controlled. And the fuel which feeds this combustion is gasoline.

The combustion happens inside the cylinders of the car ‑ six or eight of them in most cars. A cylinder is shaped like a tin can with one end sliced off neatly. However, it is much stronger than a tin can. The open end of the cylinder is at the bottom. And into it fits the piston, a very sturdy rod of metal which slides up and down into the cylinder. At the top of the cylinder are two valves which open and close. One lets in a spray of gasoline. The other lets out waste gases ‑ or exhaust. At the top of the cylinder sits the spark plug, all ready to give off a spark and make an explosion at the right moment.

Four things happen to force the piston to move up and don inside the cylinder. Let's catch the act when the piston is down, almost to the bottom of the cylinder. The cylinder seems empty. Actually the intake valve has poured in a mixture of air sprayed with gasoline. The gasoline evaporates and becomes vapor, or gas. This is the intake, or filling up step.

The piston now moves up, squeezing the air and gasoline mixture, making it even more explosive. It is squeezed or compressed into one sixth of its original space. This is the compression step. It is the moment the spark plug waits for. The plug sends down a spark and the compressed mixture in the cylinder explodes. This is the explosion step.

In an explosion gases swell up and suddenly need more room. In a car cylinder the explosive push is equal to a ton and a half. It cannot budge the sturdy cylinder but it does force down the piston.

Step four is when the exhaust valve opens to let out the waste gases. The cylinder is now ready for another charge. Intake, compression, explosion, exhaust and the piston is driven up and down, up and down.

But how does this make the car run? The piston has a series of arms and elbows which connect with the engine. The piston pin is a metal rod fitted firmly to the piston. As the piston mows up and down so does the piston pin. The other end of the piston pin is fixed with an elbow to the connecting rod. The other end of the connecting rod connects with a crank pin on the engine crankshaft. As the piston moves up and down these connecting arms and. elbows force the crankshaft to turn, turning the wheels.

All these bits of machinery must work together smoothly to make the car run. But it will not run unless the pistons work up and down in the cylinders. And the pistons cannot work without gasoline to make their explosions.

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