Lots of new car engines these days are built with both port and direct fuel injection. On the surface, that might not make much sense. Why would a carmaker use two different types of injection methods on an engine? It makes things twice as complex, and adds weight to the car. Well, it turns out there are a bunch of good reasons why it’s done.
Jason Fenske of Engineering Explained breaks it down in his latest video. There are lots of benefits to both methods of fuel injection, and it turns out manufacturers can use either one (or both at the same time) depending on an engine’s RPM range for maximum power or efficiency. For example, using port injection means the fuel can cool down the intake air before it reaches the combustion chamber, increasing air density and allowing for more fuel to be used, and therefore more power. Port injection is used at low RPM for better air-fuel mixing, which results in a more stable, efficient combustion.
Direct injection, on the other hand, cools the air inside the cylinder, greatly reducing the probability of knock. This means the engine can advance timing and run more boost before running into issues. Direct injection is used at high RPM to cool the chamber at high loads and create the most power possible.
Writer: Brian Silvestro
Published: Feb 16, 2019
Source: Popular Mechanics
Photo Credit: Cycleword