Ideal IC tube diameter

Slysc

Registered User
I'm ordering the tubing to fab up my new front mount IC tubing and I'm wondering if I should go with 3" or 2.5" diameter tubing.

My intercooler has 3" inlet and outlet so I figured I would go with 3" but I could save some dough and adapt it down to 2.5".

I'm figuring 3" would have less restriction but 2.5" would have more velocity and less air volume between the MAF and the engine. 2.5" would probably be easier to package. :confused: :confused:

So I'm taking a poll. What would you do?
 
How many CFMs will your blower do?
What is the CFMs of your intercooler?
If you have a stock intake manifold & plenum they will not flow
enough CFMs That a 2.5 OD I/C tube will.
A 2.5 OD tube the substract the wall thickness of lets say
.065 has a ID of 2.370.

The ID of a stock I/C intake manifold plenum is 2.389 to 2.400

The manifold intake hole is 3.69x 1.44 which is 5.31 sq inches.
or equal to 2.66 pipe.

So for a 2.5 od pipe with a 2.370 ID will flow enough for a unported
plenum.That is a puny 2.400 max.

I have a manifold & plenum that will out flow a three inch tube.The I/C
tube is allso a plenum as is the intake manifold & intake manifold plenum.
(stored air) So bigger is better. 3inch.

You can figuar up the amont of air needed by your engine with the formulas
I had writtin the other day.And you will see how much air you need to flow
through your I/C system.

I believe you need a min. of a 2.750 ID tube 3inch OD.But your manifold
& plenum needs to be opened up to flow for this.

RANDY
 
Last edited:
Randy,

Thanks for the info. My lower manifold is ported about as much as I can without welding more material to it. My upper manifold has been ported but I didn't open it way up because have been running the stock IC tubes.

The intercooler core is 3" thick, 12" high and 24" wide, it is a bar and plate style with internal fins made by Hybrid. They said that it would have a .5psi pressure drop at 15 psi tested at 900 cfm.
 
Dan,

Go as big as you can fit under the hood and if you can use aluminum tubing, that would be even better. 3" OD should be all you'll ever need.

David
 
I'll plan on buying 3" aluminum mandrel bends. If I buy all the 180s and 90s and 45s seperate, It comes to around $450 in just bends. :eek: I can save a lot of money if I buy all 180s and just cut them up to make the angles I need.

I may regret it because it could be a lot more work but I guess I'll order the 180 U bends.
 
YIKES! Why bother with aluminum??? Mild steel is just as good and dirt cheap. I have 3" on mine but you can also get 2.75" and since the steel is so thin, you don't lose much on the inside. I'd go 2.75" 18ga steel if I were doing it.
 
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