Originally Posted by aasaa666
Another thing, I know this is the stupidest question in the world, why would buying a better brand header be any better than a cheap one? the pipes look the same to me.
So why would people still want straighter piping?
I just recently got an AEM Short Ram intake and was trying to find published power gains on it. While browsing through all the previous 'intake' posts, one main question that kept coming up was about what's the difference between AEM and generics, is it the filter?...is it the tube? and so on. There's many people in here that know quite a LOT about cars, way more than me, but hopefully I can provide some insight from an engineering POV being a senior mechanical engineering student.
In fluid flow(air in this case), there are two things that create losses in fluid flow(referred to as headlosses). The first is the friction on the inside diameter of the tube. The second is due to bends(90 degree elbows, etc.) and orifices(such as reduction in the crosssection). There are equations which allow you to determine how much headloss is present in the system.
The friction is due to the roughness of the interior of the pipe, slowing down the air velocity, especially near where the air and the pipe contact. I looked at the interior of my AEM tube and it's pretty rough, but I have not compared it to other generic tubes. The second is due to bends, etc. creating areas where air gets trapped and recirculate in the corners not really going anywhere. This turbulent 'trapped' air interacts with the air trying to flow past, slowing it down also.
So all in all, we want 'laminar' flow, flow which is smooth by not having the flow obstructed. So whether in an exhaust, intake, or header, the idea is to have smooth straight pipe. The air filter also plays just as crucial of a role, you want the best air flow possible, without sacrificing filtering capability. The reason a cold-air intake produces more power gains than a short ram is though the pipe curves more and has more distance to travel, the cold, more dense air makes up for it. And yes, a short ram is way better than the stock box, just compare the inside of both and refer to everything I've said here.
And as stated before, intake, header, and exhaust all work the best when used together. Why? They are all in the same 'breathing' system of the car, therefore they are all dependent upon each other to a degree. If air comes in smooth, you want it to exit smooth.
No, exhausts, header, and intakes are not hypes, but what does play a factor on how well they work is...how much better they are than their stock counterparts(like stated above, the stock accord header is pretty good already)...so it also depends on the car. Hope this was what you were looking for.
One more thing, bends are referred to as 'minor' headlosses, whereas pipe roughness creates 'major' headlosses. So roughness is what you need to look at when comparing intakes, exhausts, and so on.