Harnessing air and water
The indirect charge-air cooling system in the 718
Motor racing, as usual, was the catalyst of change. In the early 1970s, the idea that a turbocharger—not just increased displacement—could help optimize engine power began to percolate in motor-racing circles. Powered by exhaust flow, turbochargers compress the intake air and pump it into the combustion chambers in large quantities; the additional air forced into the combustion chamber increases the power. In 1974,
It was soon discovered that engine efficiency could be further improved by cooling the hot charge air; as soon as the temperature decreases, the air density increases, and with it the volume of the air in the cylinders. The result: more power. So in 1977,
However, the 911 uses a rear engine, whereas the 718
Here’s how indirect charge-air cooling works: the combustion air is sucked in and filtered through the air-intake opening on the left side of the car’s body. From there it flows into the turbocharger, where it is compressed and reaches temperatures of up to 170 degrees Celsius. This is where the cooling comes in: the hot air is fed into the integrated charge-air cooler on top of the engine and cooled by plate fins, transferring the heat to the water of the low-temperature circuit. The heated cooling water is then routed into two laterally positioned low-temperature radiators and put “on ice” to be reused in the cooling circuit. Meanwhile, the combustion air—now at the perfect temperature—flows through the throttle valve into the combustion chamber, where it unleashes the power that catapults the 718 forward in a fraction of a second.
By Thomas Fuths
Illustration ROCKET & WINK