intake size for turbo

[91-gsx]

hey guys, if you have a turbo with the inlet size of 3" you could use a 3" intake and it would flow all the air the turbo would ever need. if you have a 4" inlet on a big turbo you get a 4" intake to flow the most air into it. but if you have 14b could you use 2" tubing for an intake? i was wondering becuase i have some 2" tubing laying around and i would like to make a cold air intake. the spearco intercooler i have has the inlet and the outlet on the same side, so there is not enough room for a 3" intake where my stock sidemount use to be. so thearetically speaking, a 2" intake is enough to flow a 14b, right?
thanks in advance

 

[kraka]

I am probably wrong since I have never measured the piping, but I would think that the stock intake piping is already real close to 2"...So, although there is a chance to make the car sound louder, I doubt a real performance increase would result from hooking it up to the 14b...I would go 3" if anything, and just put in the $$$ to make your own instead of the 2"...But, whatever you wish,....

 

[91-gsx]

im going for the temp. drop not the sound, although i have heard it sounds nice . but i am just wondering if the 2" intake piping would be restrictive? and if it is, then why is a 4" intake tube not restrictive for a 4" turbo inlet, like the forced performance intakes?

 

[kanderson111]

The stock intake starts out at 2" and is approximately 10" long. From where the 2" inlet hooks to the turbo, it quickly tapers to 3.125" over the course of the 10" length, so only a very small part of the tube is actually 2". If you plan on running 2" tubing from the turbo inlet to the smic location, (which is approx. 15-16"), the small temp. drop would not even begin to make up for the added restriction. In tubing an inch of diameter makes a huge difference when it comes to volume.

 

[91-gsx]

i understand what you are saying, but why is it that people get a really big intake for the 14b inlet but then stick to a 3" intake for a turbo that might have a 3" inlet. i previously thought the way you did, even thought of getting or making a 4" intake for the 14b. but seriously why doesnt forced performance use like a 6" intake for their turbo with a 4" opening, it would be a restriction in the same sense this is, right?

 

[sweet97]

Physics. My Holset has a 4" inlet for the MWE inlet to the comp wheel so I'll go back to my 60-1 with a 3" as a better example. A 14B and a 60-1 each can possibly flow so much air. A 3" pipe you might think would flow 50% more than a 2" pipe but it can actually flow more like double or more. Someone with fresher math knowledge could give you more exact figures. My FMIC has both intake and outlet on the passenger side and I have no trouble running a could air intake. Mark

 

[QuienesTuPapa]

In tubing an inch of diameter makes a huge difference when it comes to volume.

He's right. For instance, lets take two pieces of pipe: One 2", and one 3" both 10" long. If you calculate the volume of the 2 and 3" pipes you get 31.4 cubic inches and 70.1 cubic inches, respectively((pi*r^2)xL). The 3 inch pipe has over twice the volume of the 2". Theres a reason that the intake was designed to taper instead of matching the inlet of the turbo the whole way. Engineers aren't stupid...most of the time.

 

[91-gsx]

but the thing that is hard to swallow is why does a turbo with a 3" inlet work perfectly with a 3" intake, but a turbo like the 14b not work well with a 2" intake. i understand that a bigger tube does hold more air, but when it comes down to it it will go into a 2" inlet. sweet97, if you have a picture of your intake setup with the inlet and outlet of the intercooler on the same side i would greatly appreciate seeing it. and another thing, i might even go as far to say a 3-4" intake on a 14b could cause turbulence because the air is being drawn in through the filter and going through this big pipe, and then it slams into a small opening. I'm not trying to argue, but it is almost like the argument against having big intercooler piping, like 3", and then having a really small throttle body, most just swap the throttle body out for a 3" one because they know it is a bottle-cap. in the case of the 14b, you cant do that.
great replies thanks

 

[Enilator]

My unedumacated guess would be that the 2" inlet to the turbo is going to flow as much as the 14b can take in but the reason they use the tapered ones that get bigger up top is mainly to funnel it down instead of just having a square box with a 2" hole for the 2" pipe in the middle (THAT WONT FLOW GOOD). Now I'm sure like everyone is saying the 3" tube will flow better YES, but i would think that the silicone reducer to make that 3" intake tube to a 2" (turbo inlet) would form a bottleneck and slow air down due to turbulence at the reducer and therefore slow down the air to the 2" size anyway??? I would guess theres hardly a slight increase in hp comparing the two but trying to stretch a 2" pipe to outlet size of the MAS would make it pretty weak and thin i would think. Just my .02....................................

 

[91-gsx]

i do not have a mas ont he intake it is a blow-thru. and the way i wanted to do it is make a 2" intake to the stock intercooler location and then put a reducer from my 3" filter to my 2" piping. that way when i am at the track i can also run it open, without a filter and get a ramming effect, i still do not know if i am going to do that though.

 

[Turbocharged]

You would be better off using 3" piping and using a reducer at the turbo. Preturbo flow is important for a couple reasons. Most notable is the superficial velocity of the intake charge. Because we have turbocharged cars, the preturbo superficial air velocity is very high; even higher than the post turbo velocity if under positive boost. This may be hard to conceptualize, but a simple mass balance will prove the point. Because air is flowing at a higher velocity before the turbo, it is important to keep restrictions to a minimum. Small pipe diameter or sudden bends in the pipe will hinder performance.

I wouldnt suggest running without a filter at the track either. Unless you are not concerned with debris finding its way into your compressor blades. It doesnt take much to ruin a turbo. (boost + open filter + debris + high compressor RPM's = dead turbo)

 

[sweet97]

91-GSX my set-up wqould not help you as I don't run a turbo that outlets on top like yours. Mine outlets facing down. I would spend time and cash for a turbo upgrade as you have a lot of the supporting mods in place. The effort put into a CAI may not benefit you worth the effort applied. just my .02 Mark

 

[OneGeeAWD]

ive got an evoIII 16g that i'm about to put 4'' FP intake pipe on with their custom silicone adapter. once i get my front mount ill actually be able to fit the damn thing (upic pipe is in the way of the filter). ill post any problems i incur. i know its not the most controlled experiment since ill be putting the fmic in at the same time but what can you do?