rahenry00

iTrader: (4)

OK I got into a discussion with a friend of mine last night...he's a mechanical engineer designer, and we started talking about ebay air intakes. And he started talking about the disadvantages of them, starting obviously with the filter (we all knew that), but then he caught me off guard and started talking about the metal itself. I figured he would be chastising the bends in the cheapo tubes, but he said the metal they are made of makes them useless. He started giving me a long example of a tuning fork, its metal density, its surroundings, and movement of sound waves/air between the forks while they are vibrating. It made alot of sense, I trust the guy, we were college roomates in college, and he designed a super mileage vehicle (800 miles on a gallon of gas). So I doubt he was talking smack. Anyone else have any thoughts on this?

carter

Waow? Tell him to meet up with some manufacturers.

IT would help the mandated 35MPG by 2012 for shore. Makes sense to an extent but you always gotaa test the theory. TEll him to try it out and tell us.

So are the AEM and K n N intakes better?

gearbox

iTrader: (95)

well yeah, mandrel bent pipe made of smooth metal will flow air faster than cheap metal that is rough. i know the weapon-r has a super smooth interior pipe from filter to the tb, it feels like glass. if you ever checked out cheap exhaust pipes at the auto store, they are very rough and still contain some metal "burrs" around them. and i know someone is gonna say small things dont matter, but they do. an ideal intake should have a really good filter that flows alot of air, filters alot of dirt, and has a velocity stack. pipe should have a dual chamber design with super smooth interior and no sharp bends. a heat resistant outer coating like powdercoat will help keep the pipe cool, altho since air is moving so fast, it will not have alot of chance to heat up. shielding the header should be a bigger improvement by reducing overall engine temps. once the air reaches the TB, it does not have to be moving as fast, and so the end of the pipe can be roughed up to promote turbulence. this will happen in the IM anyway, and further when the air passes over the rough surfaces of the intake ports and to the chambers. it all adds up in the end, if the car is able to use the extra/faster airflow. hint hint turbo cars.

d17civickid

iTrader: (4)

in my opinion the intake piping is just a piece of piping. i mean just because you got aem doesnt mean you are going to make more hp. it really doesnt make a difference. at least not a noticeable amount. plus how much hp do you expect to get out of an intake? lol

TRIZ

iTrader: (14)

^thats aside from the point and steering in the direction of- "hey its a civic, give up before you start modding" Every little bit helps. If you want to cut corners and buy the cheap **** that doesnt have any R&D behind it, be my guest- but please dont put down those that care about getting the most out of their engines.

513steve

you get what you pay for

MadDawg15

i'd have to take a middle ground here. yes, having a rougher pipe will lead to more skin friction causing the air to slow down and create more separation from the edges of the pipe causing less air to flow. however, this affect should not be too drastic. when the hp gains are so minimal anyways, the affect should be pretty small

briand17a2

Inside diameter boundary layer adhesion will increase with more surface area (e.g. roughness / lack of polish) but for an intake tube mated to a stock intake manifold, really, who cares.

PV = nRT <-- Ideal gas law, where

P = pressure (in atmospheres)
V = volume (in liters)
n = number of "moles" of whatever gas were talking about
R = ideal gas constant, cant remember what it is right now
T = temperature (in degrees kelvin; deg celsius - 273.15 = deg kelvin)

What does matter however, is the insulative property of the intake piping. For a given volume and pressure, cold air will have more molecules of oxygen than the same volume of "hotter" air. This is because the air density varies as a function of temperature, blah blah blah, cold air intake yo.

The boundary layer is the region of flow inside the pipe where the "fluid" (in this case, air) is "sticking" or adhering to the pipe wall (due to electrostatics, same thing that makes scotch tape do its thing). The cross-sectional thickness of this boundary layer depends on a number of factors, but for more info on that, check out wikipedia.

In general, the boundary layer of air does not move down the pipe. As such, this boundary layer also acts as an insulator; one of the reasons people use double-paned windows in their homes (heat conducts slower through the air-gap between windows).

But, if the inside of the pipe is rough, we have more surface area for heat transfer, so more heat gets into the boundary layer per unit time, and the boundary layer air is, on average, hotter, leading to faster heat transfer to the laminar flow region of the intake charge air.

So, from a thermo standpoint, the best pipe interior (for the intake piping only, not the intake runners however) would have a mirror finish.

Mass-wise, the pipe thickness should only be as thick as structurally required. Super thick pipe may hold more heat energy, but for the same specific heat capacity, all thicknesses will eventually transfer the same amount of heat to the inside per unit time.

So from a thermo standpoint, you want a metal that can absorb a lot of BTU's before increasing in temperature by one degree whatever (see specific heat capacity).

So technically, yes, the metal selected does have much to do with the performance of the intake piping, and the performance of the engine.

BUT...your particular boreXstroke has WAY more to do with performance than whatever the hell your intake pipe is made of.

So, as long as the pipe is structurally sound, as straight of a shot as possible, and a good free-flowing air filter is used, it really doesnt matter what metal you choose.

Best suggestion for ebay intake materials: wrap in thermal insulation and use heat shields to keep radiant heat off of the pipe. Unpainted sheet metal works great for a heat shield / reflector. Make sure the intake draws in fresh air from OUTSIDE the engine compartment as possible for your particular design.

briand17a2

but by no means use a pipe of less than 2" ID, unless your boosted, and if so, FTW