 Air. Fuel. Compression. Spark. That's the recipe for power. And that hasn't changed since the invention of the internal combustion engine. But the way that recipe gets put together is constantly evolving. And the fuel delivery process has probably seen the most change in recent years. Try to remember some of the basics of CQC. We could start off by talking about carburetors, but I need your daggum, Pappy, so go talk to him about that old crap. Every new production car sold since the early 90s has used some form of electronic fuel injection. From then until now, the most common design has been port injection, but getting more popular every year is direct injection. The main difference is where they do their duty. Port injected cars locate the injectors in the intake path for each cylinder and spray fuel prior to the intake valves. The fuel mixes with incoming air as it makes its way toward the head, then through the intake valve port and into the combustion chamber before things get all sparking. Direct injectors, as the name implies, are positioned to spray fuel directly into the combustion chamber. The driving force behind the growth of direct injection is largely due to government regulation and consumer demand for increased fuel economy and emissions control, but there are some benefits for gear heads too. In order for the air fuel mixture to properly burn, the fuel needs to be vaporized before the spark. As a result, direct injected engines have to use a secondary fuel pump that takes the low pressure fuel from the tank and cranks up that pressure anywhere from a few hundred to a few thousand psi. That high pressure fuel improves atomization and vaporization, which cools the combustion chamber and allows for more aggressive tuning while minimizing potential engine damage. But there's some downsides. Direct injected systems are more complex, which means there's more parts that are more expensive and more of a challenge to maintain, especially when trying to make lots of power. With port injection, if you exceed the flow of your current injectors, you just slap some bigger ones on. What? But that's not so easy for direct injected cars. In fact, most of them don't even have the option for bigger aftermarket injectors. Another major issue with direct injection comes with age. Any combustion engine has oil vapors and little bits of carbon that make their way all throughout the system and eventually they find somewhere to deposit themselves, like the back of your intake mills. On a port injected car, fuel gets sprayed right onto those valves and works as a solvent to keep them clean. But direct injected cars skip that step and eventually build up lots of gunk on the back of the valves, meaning lost performance and economy until you spend the time and money to clean them, which is eventually necessary with all direct injected cars. But in some cases has to be done as often as every 25,000 miles. At the end of the day, port and direct injected cars are still really common and both the OEM and tuners are still figuring out the best way to use them. So it's important for you to understand the pros and the cons when deciding what car you want to buy and how you want to modify it.