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!!

[dlx742]

Not true, because the 2" outlet of the turbo on the compressor side is under pressure. Take that jug (coke bottle) and time how long it takes to drain out when you turn it outside down. Now, take that same jug and time how long it takes to drain out when you turn it upside down and apply pressure (squeez) the bottle. The opening diameter of the bottle didnt change, nor did the amount of water inside the bottle. The only difference was the pressure added to the bottle which allowed it to drain faster.

Thats very true. You move more air under pressure then not. Thats how a turbo car can ingest more air then an NA car through the same sized pipe.
But the bigger intake will not add any more pressure to the system. All it is creating less restriction. So any gains would have to assume that a 3in intake is too restrictive.
Ultimately the car will make more power when more air is able to reach the cylinders. But you have to remember that a 3in intake is still bigger then your throttle body, and intercooler end tanks. All those things limit how much air can enter the engine. I think that you would have to upgrade ALL of those components to see a gain. Thats why you always see people with higher HP cars upgrade the throttle body, intercooler pipes and intake all at the same time.

4π(v1)=1.89π(v2) or v2= 2.12(v1)

I got... v2=2.11(v1)

2.116 rounded up since we are at 2 sig figs is 2.12