cold air intake size

[quang]

hi guys just a quick one, how big is the pipe size for the cold air intake that goes down into the front guard, if its smaller than 3inch would having a 3inch pipe going there, be bad?

[ToFuBoi]

check if it can fit through the resonator hole under the airbox.. should be 3"

[quang]

it fits, sorry should have been a bit more clear, would having a 3" pipe at that length, cause its a fair bit pipe to get there, put a downside on performance? isn't sorta like having two straws one short and one long, the shorter will be quicker to suck air through than the longer one since it has less distance to travel and pipe to fill, but if you have the longer one a bit smaller in diameter, it can suck air quicker than before cause of less pipe to fill up, sorry not very technical but i hope you get what i mean.
or
forgetting all of that crap that i just said, what is the size of the cold air intake pipe?

[^_^civic^_^]

So are you more worried about the length of the pipe? or the diameter? :confused:

Well, let's put it this way, if u have a short pipe, in otherwords a short ram, instead of a full CAI, then yes, like you think, the air will reach the engine faster from the filter. BUT, you will be taking in hotter air (within the engine bay). Hotter air = less dense = less air into ur engine. But so far most tests show little difference between Short ram and CAI...it's just your own preference.

Now gettin back to what you were sayin about pipe length in respect to the air reaching the engine. I'm gonna get a little technical here, so bear with me hehe. Yes, a smaller diameter pipe = faster air velocity in the pipe...BUT the VOLUME of air (the mass flow rate) is not improved. No matter the diamter, at any one RPM, the mass flow rate will always be constant under ideal conditions. So if you understand that, then the engine will effectively be obtaining the same amount of cold air into it no matter the pipe size (ideally). However, in the real world, this wouldn't be true. The reason for having a larger diameter pipe (3" over 2") is that the flow of the air in the pipe will not be restricted so much. Bigger pipe = freer flowing air due to less friction losses. Freer flowing air = faster mass flow rate = more air gettin to ur engine faster. Thus, having a smaller diameter intake pipe would restrict your air intake. Basically, smaller pipes increase friction which leads to a less efficient system.

OK, so if you consider all this, the CAI does all the above with cold air. The pipe lengths are longer, and thus mroe air friction. The short ram which uses hot air, has less air friction. Thus, both systems have ups and down to them, hence explaining possibly why the two systems perform comparatively. Now this is just basics of fluid flow, if n e one else wants to get more technical they can. :D

I can't quite get what you wanted to know exactly, but i hope what i've said helps.

Laterz man

[quang]

hey man that helps heaps and i'm fortunate enough to understand what your talking about, i guess what i was trying to get at is for the length a particular length of pipe you can have an optimum size for when pushing air through it at a certain rate for having the pipe filled up with flowing air . like an exhaust, go 2.5" can be too big go 2.25" just right, so i'm just wondering if 3" is too big for the cold air intake at that length, or should i be using something smaller. but i guess in the end it doesn't really matter thanks :)

[iced]

aftermarket cai system range from 2.5 to 3inch.

check here http://www.tprmag.com/issue/1/ca-injen1.shtml

2.75 inch piping is hard to find and costs more than 3inch piping.

intake works on air volume inside the piping.
if you have a short ram ok 3inch is good. but when you make it longer you should reduce the diameter.
imho some sort of restrictions give low end torque.

BTW
i doing a full stainless diy intake for my mitsu mirage.
ive just got 2 90deg stainless bends off ebay for 18$ each. + bunch of tbolt clamps
2 size choice 2.5 or 3 inch. im also choosing whether to go 2.5 or 3.
the seller also has 3 inch 45 degree stainless bend for 18$

i can do it with 3inch 45deg and 2 3 inch bends.
OR
3x 90deg 2.5 bends, cos seller doesnt have 45deg bend in 2.5in

the choice is whether 3 will decrease efficiency.
PLus my TB is 2.75.
attaching smaller piping next to my TB is kinda a gamble even with a 2.75 - 2.5 inch silcon adaptor (or 2.5 inch hose sretched out on TB side).
might get rubber for stretching because silicon wont.

[twilightprotege]

ideal size for ANY, yes ANY intake pipe work (sri or cai) is 125% of the diameter of your throttle body

in my mazda astina sp20 the throttle body is 55mm. that times 1.25 = 68.75mm (2.7")

so the closest to that is 2.75" (and which allows for wall thickness too). any smaller and the volume of air wont be there, any larger and the air speed wont be there.