FAA Powerplant Written Practice Test

What is the purpose of an after cooler on a turbocharged reciprocating engine?

1. To increase the density of the air

2. To cool turbocharged air entering the induction system

3. To reduce noise from the engine

4. To enhance fuel vaporization

The correct answer is: To cool turbocharged air entering the induction system

The purpose of an after cooler on a turbocharged reciprocating engine is to cool the turbocharged air before it enters the induction system. In a turbocharged engine, air is compressed to increase its density, allowing for more air to enter the cylinders and improving the engine's performance. However, this compression generates heat, which can reduce the air's density and negatively affect the combustion process. By utilizing an after cooler, the heated air is cooled down, which increases its density as it enters the induction system. This higher density air leads to better combustion efficiency, improved power output, and reduced likelihood of knocking. The after cooler essentially helps maintain optimal engine performance by ensuring that the air entering the engine is at a cooler, more effective temperature for combustion.