Thread: Is changing the intake pipe size multible times bad?

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Not really. What maf are you using that's 4"? That's a pretty damn big MAF...

My intercooler has 2.5" in/out, and I ran 2.5" hotside, 3" coldside. MAF is a Z32, and TB is Q45 3".

Is there a difference? Yes.
Is it a big deal? Depends on how anal you are about efficiency (and from the looks of the end tanks on that IC, I can assume you're not terribly anal and more interested in making it actually fit in your car nicely).
Are you doing blow through or draw through?
If draw through just make your turbo intake pipes 4" and then do 3" (reducing to 2.5" for the IC).
If blow through, do 3" pipes as well with the appropriate reducers.

If you have a 3" throttle body though, and are willing to run 3" charge pipes, I'd seriously consider an intercooler with 3" in/outs.

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That all depends on WHERE the leak occurs. If it's between the MAF and TB, you're suckin just like in draw thru. If you go draw thru, the only downside is the BOV configuration, which isn't a big deal anyway. I have yet to see anyone really tell a difference between draw thru and blow thru setup.

Please don't use the Lighting on blow-through. Please.

The pipe size changes are going to mess with maf readings a lot.

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I hate to kill you hopes and dreams but that core is one of the worst designs there is. I would keep looking if I were you.

What turbo are you using? Do you care more about practicality or performance? It looks like the practicality has been covered pretty well by the other guys. If you want max performance match the pipe to the power you plan on making.

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Performance and limiting inconsistencies, minimizing pipe all go hand and hand, so you are on the right track.

Shoot for 2.5in every where you can with the pipe...Wait what kind of power goals?

Are you getting a smaller width rad or like a civic rad or what?

I ran both pipes on the same side of the stock rad on my NX and moved the rad over you might find it easier to do it the same way just because of the larger pipe you are working with. I could probably work 3in pipe in the same space if I played around with the sheet metal. Just something to think about

What chassis are you working with? If you have something other than b13 this might be way off.

As far as IC cores you would be much better off to just use 90 bends off the IC pipe instead of that nasty core. It would be a good idea to start looking at some of the top to bottom feed ICs too. They are going to be the best design/flow wise. Defiantly go this way if you end up going around both sides of the rad