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?

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

I figure 2" gives a lot more room to work with in bends etc

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

yeah I'm not shooting for 300hp with this setup, most likely I'm just wanting ~200-220rwhp in the end... but who knows

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.

you typically don't need 2.5" until you need a t3/t04.

I'm planning on 2" right up to the TB.

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.

right I dont run a t3/4 so 2.5 is overkill.

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.

Mine is built 2 before and 2.5 after.

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.

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.

so does it really matter? 2 or 2.5"?

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.

thanks a bunch guys, think I'll stick with 2" for simplicity and ease

some one should change this threads title to does size realy matter :lol:

i don't think she's gonna care if your pipe is 2" or 3" :gay:

heh i just asked this in another thread.

some thoughts (no science to them):
changes in flow area are a restriction. you want smooth transitions (not steps)

the flow after the IC is probably very turbulent so larger tubing might help flow.

stock throttle body is 2.5... for flow? people run larger throttle bodies for some reason.

the IC is the limiting factor anyway.

hmm.

well there has to be a step somewhere even if the IC is limiting

but really I doubt there is much, if any, difference

I did some searching and found similar stuff...I'll just try to copy your I/C setup :)

that was.... step as opposed to smoooooooooooove transition. like changing the diameter by a half inch over a half inch or over 4 inches.

2-inch is fine for your goals.:cool:

2 inches end to end here and I'm running a T3/T04B (soon E).

i'm running the same

Yeah shell still ask where the other half is :gay: :rofl:

well shit, since mine is situated well, Im going to leave well enough alone.
thanks

Ive stopped searching at m.net about things like this that might be a grey area because of the smug cloud around that forum

FWIW, the rear-mount camaro guys run huge pipes up and down the entire length of the car and they have zero problems with lag or making power. The turbo and the engine both flow such an enormous amount of air that the volume of the pipes are completely immaterial.

I think you will get bigger gains just from avoiding lots of unnecessary turns and unnecessary pipe diameter changes. That is more of a flow-related argument than a volume related argument. My thinking is that if the outlet on my T04E compressor is 2", how much gain am I going to get from running bigger pipes?

There it is. :cool:

+1