Oxygen Sensor (O2) Yup, that's right it's a
sensor and it allows the PCM/ECM to read
the amount of oxygen in the exhaust. Before we
get started on how an O2 sensor works, I suggest
watching this short video on ions.
Intake Air Temperature Sensor (IAT)
You guessed right, this sensor allows the
PCM/ECM to read the temperature of the
air the engine is about to inhale and use
for combustion. Why do we need to know
the temperature you ask? Well, cold air is more dense than hot air and engine performance is all about mixing the correct amount of fuel with oxygen.
If you're just back from the 4 stroke theory video get ready to learn. There have been some major technological advances that have made this process happen pretty efficient. Ok, I take that back we can say it's a lot of things, cool, powerful, bad a#@, loud but efficient is something humans are still working on. In the early stages of the internal combustion engine most of the engines controls were completely mechanical relying on engine vacuum and speed to control the engine and produce the most efficient power possible. The computer steps in and what was impossible with engine control now becomes possible. Below you will find a list of sensors that help an internal combustion engine run.
If you were hoping to read how to cut your muffler off and get 500hp out of your Civic, just go get yourself a hacksaw and have at it. The blade is directional so you want to make sure you only push down on the forward stroke. If you're still reading maybe you're re-thinking that idea. You may have passed the HSPA but what are the odds a team of highly educated engineers over looked the fact that all they had to do to double their horsepower was leave that pesky muffler off.
Engine performance is a study of the controls that make engines run, not only down a 1/4 mile drag strip but to the grocery store or that family road trip to Florida. The complexity it takes to get a stock car to function over a wide variety of terrains and weather extremes reliably is a more difficult task then getting your late model Camaro to hit the 13 second mark at the drag strip.
Don't get bummed out that in two paragraphs I haven't revealed how to bolt on that anodized red egr block off plate and get an extra 50hp. If you want to be able to set a car up for a specific task and increase it's performance for that task it's going to take a very thorough understand of the controls that exist to make your engine run stock and while my understanding may not be thorough enough it's a pretty solid start for someone who just put down the hacksaw.
A solid understanding of four stroke theory is required before we go any further, so if you haven't had the pleasure of hearing about suck, squeeze, bang and blow you need to start there.