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Old 01-27-2007, 09:24 PM   #1
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Default Does the pipe size really matter?

Currently I'm not running an IC, but I'm piecing this together still. I've got an intercooler that I'm going to use and it has 2" inlets/outlets. Anyone know the outlet size on the GT2560 turbo from the FM kit? I can't remember offhand.

Anyways, does the pipe size really matter? Say I run 2" from the turbo to the IC, should I keep 2" up to the TB and just use a transition or bump up to 2.5" (think thats the TB size) after the IC all the way to the TB. Does it really make a difference at all?
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Old 01-27-2007, 09:33 PM   #2
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it will effect flow eventualy and intake velocity as well as turbo spool but in the hp range you are likely to acheive sub 300whp i dount you notice to much difference
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Old 01-27-2007, 09:34 PM   #3
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I figure 2" gives a lot more room to work with in bends etc
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Old 01-27-2007, 09:52 PM   #4
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I was thinking smaller diameter pipes would help spool and hit max boost earlier.

maybe it would limit peak HP under what it might be, but if I hit boost a little earlier wouldnt it be worth it?

I have 2.5 all around, I was thinking stepping down to 2" on the compressor side of the IC
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Old 01-27-2007, 09:58 PM   #5
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yeah I'm not shooting for 300hp with this setup, most likely I'm just wanting ~200-220rwhp in the end... but who knows
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Old 01-27-2007, 10:10 PM   #6
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It would be interesting to see a comparison between 2" and 2.5" charge pipes. I would suspect that the larger volume of air held in 2.5" pipes would offset any gains in velocity. Actually, I think velocity isn't that important in a boosted application.
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Old 01-27-2007, 10:25 PM   #7
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you typically don't need 2.5" until you need a t3/t04.
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Old 01-27-2007, 10:36 PM   #8
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I'm planning on 2" right up to the TB.
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Old 01-27-2007, 11:16 PM   #9
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Quote:
Originally Posted by hustler View Post
you typically don't need 2.5" until you need a t3/t04.
it does seem like over kill to me. but I'll deal with that later
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Old 01-27-2007, 11:20 PM   #10
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Quote:
Originally Posted by VRTSid View Post
it does seem like over kill to me. but I'll deal with that later
from what I understand, tubing size is more dependant upon displacement and volume, not pressure.
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Old 01-27-2007, 11:51 PM   #11
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right I dont run a t3/4 so 2.5 is overkill.
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Old 01-28-2007, 12:14 AM   #12
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I'm running 2.0" pre-IC and 2.5" post. works for me. Plenty of systems have been built with 2.0" all around.
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Old 01-28-2007, 01:02 AM   #13
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Mine is built 2 before and 2.5 after.
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Old 01-28-2007, 01:12 AM   #14
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Mine's 2.5 all around. The only adapter is from the commpressor to the first intercooler pipe. My intercooler has 2.5" inlet/outlet, so I bought a 2.5" universal pipe kit on ebay.

Note: 2.5" leaves little room to work within the space provided for the pipes, and t-bolt clamps included in ebay pipe kits SUCK. I broke 5 after driving on the salty roads.

Last edited by SamS; 01-28-2007 at 01:28 AM.
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Old 01-28-2007, 01:20 AM   #15
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the way i would put it is, try drinking a beverage through a coffee straw...
but i have the same problem. my solution, 2.5"-2" for my air filter to turbo.
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Old 01-28-2007, 01:25 AM   #16
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so does it really matter? 2 or 2.5"?
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Old 01-28-2007, 03:09 AM   #17
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I think if you'll do a search over at m.net, or through Corky's posts there, you'll find that he's researched this at length.

If I remember correctly, he did back to back runs on pipe size ranging from about 1.75-3.00 inches and found virtually no difference in spool/power/response/etc... In the power and psi ranges we typically deal with on this forum, anywhere from 2.0-3.0 will be identical.

The benefit of smaller pipes is (as said earlier) that they are much easier to route... and they're cheaper (both for pipe and couplers). However, almost all of the eBay intercoolers out there are 2.5" in/out and the intake manifold inlet for 1.6 and 1.8 motors is also 2.5".

Depending on your turbo, the compressor outlet can be anywhere from 1.75 to 2.5". Most of the smaller T25's I've seen have been 2", which means a 2"-2.5" enlarger coupler and then 2.5" all the way to the manifold. Somebody with a T3, what do your compressor outlets run?

I run 2" all the way to the manifold, and use a 90* 2"-2.5" enlarging coupler there.
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Old 01-28-2007, 10:40 AM   #18
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thanks a bunch guys, think I'll stick with 2" for simplicity and ease
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Old 01-28-2007, 11:16 AM   #19
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some one should change this threads title to does size realy matter :lol:
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Old 01-28-2007, 11:32 AM   #20
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i don't think she's gonna care if your pipe is 2" or 3" :gay:
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