Porsche is known for often doing things backward. The 911 has a rear engine for example. However, not just the more significant items, this phenomenon is also applied to the more minor details in the car as well. Jason Fenske from the YouTube channel Engineering Explained has recently explained the intake manifold on Porche’s 718 Cayman and 718 Boxster. These models switched from naturally-aspirated flat-six power to a variety of turbo flat-four engines.
Fenske explained that most modern engines are designed to generate high-pressure air in front of the engine’s intake valves. The length and shape of the intake tract create pressure waves which push a blast of high-pressure air against the intake valve when it is opening. This sends a little extra air into the intake stroke even on a naturally-aspirated engine.
Porsche’s turbocharged four-cylinders work oppositely. Each intake tract has an expansion chamber where the intake pressure is decreased before the intake valves are opened. This expansion chamber allows the intake air to cool down before it goes into the combustion chamber. The intake air from cooler enables an engine to run a leaner air-fuel mixture. It also allows more spark advance. Since these engines are also turbocharged, Porsche was able to tune the turbo pressure to work with the intake-expansion chamber to optimize the whole system. Porsche says that its unique intake design reduces the cylinder temperatures of the engine by 20 degrees. This also leads to a 12% reduction in fuel consumption while the car has a full load. Watch this video to learn more about Porsche’s unique engine.
