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AUT1010 Module 2: How Engines Work

All gasoline engines must operate on the same four concepts:

  1. Fuel
  2. Air
  3. Spark
  4. Compression

At the core of engine performance, these are the most critical considerations. Engines are specifically produced to have a delicate balance balance of all four of the items mentioned above. Without the proper ratios, the engine may run poorly, fail to run, or even spontaneously explode. However, not all engines are reaching their full potential. Manufacturers are often forced to restrict an engines power output by dulling these ratios so as to stay in compliance with emissions regulations. In AUT2010, Advanced Automotive Technology, we discuss this in greater detail.

For now, it is simply important that you remember these four things: fuel, air, spark, and compression are the power of life in an engine. You can come up with a creative way to remember this and share it in this weeks discussion.

An engine consist of multiple moving parts, all timed to achieve the ideal ratios of compression, air, fuel, and spark. It all begins with an air intake. The engine sucks air in through a filter, past the Mass Airflow Sensor (MAF) and into the throttle body. In most engines, there is fuel injector in the throttle body that is receiving fuel from a fuel pump on the gas tank. Typically speaking, there will be one fuel injector for each cylinder in the engine, which one located in the throttle body just outside of the cylinder.


Cylinder head, valve springs, rocker arms, fuel injectors. Notice the valve that is open, the third spring from the back is compressed. 

Attached to the head of the block is the cylinder head, which holds valves and valve springs, all tucked away nicely under the valve cover. There can be anywhere from two to eight valves per a cylinder. Located in the cylinder head with the valve springs is a camshaft, sometimes more than one. The camshaft is connect with the crankshaft by way of a timing belt or chain. As the camshaft rotates, it pushed the valves open or close, in time with the piston rising and falling.

When the piston begins to fall, the valve opens allowing the air and fuel mixture into the cylinder chamber. As the crankshaft pushed the piston back up, the exhaust gases are pushed out and the valves all close, allowing compression to build as the piston reaches its apex. Once the piston has reached the top of the cylinder, a spark plug ignites the compressed gas, causing a combustion and starting the process over again.

As you can see, it is a relatively simple process, but one that requires absolute precision. See the video discussing this before moving onto the simulation and discussion activities.