4" intake on 3rd gen 3sgte, disscussion topic! GIVE YOUR 2 CENTS! Options

[presure2]

hey guys, as you know, jim now has the 3rd gen 3s in his car, and after doing some research around various boards, he decided he wanted to try a 4" intake.

now, before you all go nuts, the guys down @ hux racing in florida claim HUGE gains with a 4" over a 3" intake, and have posted some results.

here are a couple "copy paste" deals from mr2.com:

We always figured my street car made at least 280 rwhp. Until we dynoed it on our new Dynojet. The only mods are: our air intake mod 4", Blitz SBC boost controller, our 3" single tip exhaust, & boost cut defeated.

328 rwhp & 316 rwt

This is on a maxed out ct20b, stock ecu, stock injectors, genIII fuel pump, & stock intercooler. This was attained using 100 octane.

heres the dyno sheet:

The GenIII swaps we do I always push them to use our air intake mod since we have seen consistent results using that combo (4" K& N air filter, 4" inlet tube, custom coolant relocator hose).

so, with that in mind, (and the fact that hux racing wants 400$ for somthing they wont even show you a picture of) we decided to give it a shot.

since the inlet of the '20b is only 2.75" (yes, i know its a mm mesurement, but for all intents we all use a 2.75" reducer anyway..lol) we had to find a way to reduce the 4" pipe down to that.

since we couldnt find anyone who makes a 4" to 2.75" reducer, and the fact that i thought it would be kinda flimsy, if we could find one, i headed over to burns stainless to see what they had.

they carry 2 diffrent styles of "trumpets" (reducers) a longer style, and a shorter. so we got the 4" to 3" trumpet, and because of the limited room we have to work with, we chose the shorter style.
heres a pic of what it looks like, with the coke can for size reference.




once i got that in, and the coupler to mate the pipe to the turbo, i went out to the garage, and cut the pipe to set it up:



thats the basic idea, i just need to weld a couple bungs for the IAC and catch can, and weld it up.

im hoping we can get back to back dynos at some point real soon with a 3" intake vs this one, the only thing i need is a 4" k&n, or a 3" ebay special so the tests will be the same with no variables.
if everything shakes down right, we could do this on both dustin, and jims cars, to get more results on diffrent cars, to see what kinda results we can truly get.


discuss!!

[_Jim_]

Yes the 2.75 compressor opening is a "restriction." But it is not the only thing to take into consideration. Here's the deffintion of a vortex off WIKI

A vortex is a spinning, often turbulent, flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex. The speed and rate of rotation of the fluid are greatest at the center, and decrease progressively with distance from the center.

So its not as simple as how much liquid you can or can not suck throw different size straws (but I a kick out of imagineing someone in a drinking race with a SUNNY D straw ). The compressor side is spinning at incredible rates, in excess of 100,000 rpms. Air will be in a vortex state when entering into the compressor housing. So the air will be flowing into the 2.75" opening at great speeds, as described in the definition. So, the 2.75" opening in the compressor housing will be able to take much more air then a 2.75" opening would be able to take if it wasn't under vortex conditions. So, based on the definition "The speed and rate of rotation of the fluid are greatest at the center, and decrease progressively with distance from the center" you would want a bigger intake pipe to to allow for more air to be in the intake pipe at all times to use the vortex condition to its fullest potential.

So I would think that a .25" increase (3" intake) isnt going to supply the extra air needed to reap the full benifits, but I think 1.25" increase (4" intake) would.

And before people jump down my throat, I DO NOT believe that you can go endless with this. Meaning at some point gains are going to taper off and eventually stop increasing as the size of the pipe increases. So, no....there are NOT super huge, massive, out of this world gains to be had with a 8" intake