What size charge tubing should I use?
 

I'm going to be installing my intercooler soon and I need to order some aluminum tubing. My intercooler has a 22"x6"x2" core with 2" and 2.25" end tank pipes. I do not know what one I should use for inlet and outlet. I would think the 2.25" would be the outlet I guess. My throttle body is the stock 2.5" and my compressor outlet is only 1.5". I'm using the setup in my sig but I will be bumping to 10psi when the intercooler is in. I'm at 7psi right now.

What do you guys think will be right for this setup? If needed I can chop off the end tank pipes for larger ones but I think they're already close enough.

for the hot side i'd suggest a 1.5 to 2 inch as soon as possible, then 2 inch to the ic, then for the hot side go from 2.25 inch to 2.5 inch as soon as possible then go 2.5 all the way to the TB. your sig says you got a tig welder, that should make it easier, you can cut and weld the pieces back together to make tighter bends and stuff, thats what i had to do a couple times.

Welding aluminum FTW! I would go 2" hot side, and 2 1/2" cold. If you dont weld the pipes together, make sure you bead roll them or they will blow off (ask me how i know).

Ok.

So why is it that everyone seems to go from the small compressor outlet size and let the tubing get bigger untill it reaches the TB, instead of using the same size tubing all the way to the TB? It seems to me that it would lose a small amount of pressure by making it gradually bigger.

sorry to go off tipic but what kinda HP numbers are you hoping for with this set-up. im looking to do about the same

the reason is that 2" is really all the capacity you need and 2" is way easier to route for the hot side.

This

Remember that you generally want to stay below a Mach number of 0.4, while not going so big that you kill velocity, or get too much pressure drop.

I've been paying a lot of attention to this since my turbo isn't the most efficient, and I want to avoid overspinning it while keeping as high a pressure ratio as possible. I'll likely end up running 1.75" hotside, and 2" coldside.

Sound small? Do the math.

I plan to be at 275whp, at 16psi, which is a little over 400cfm. In the 2" piping this give a Mach number of 0.27, well below what Corky suggests as the drag limit in Maximum Boost.

I am doing 2.5 inch all the way, just because that is what came with the ebay kit i bought.

2.5 for me too

my setup uses a 2"-2.5" silicon 45 degree coupler from the turbo directly into the intercooler, then i have a short bit of 2.75" tubing to the throttlebody. my intercooler pipes prob dont equal 15" total. i think its smart to not grow to much on the turbo side. and to not step down from the intercooler outlet size on the t.b side.

I agree, it will kill velocity big time for such a small engine.

Take a close look at the piping used on Evos, STis in fact on many DSM who run easy 12 and 13 seconds have very small diameter stock piping.

I would not go bigger than 2.00 on the turbo piping.

So for my power goals, I was hoping for 200ish HP at 10psi. I couldn'tfind a map for my turbo so I realy don't know what it's going to do. I do know that this is the sr20det aveneir T25 journal bearing turbo from a W10 motor. Could someone do the math for this? Or give me a formula to do it?

I have turbocalc but I don't think I have any maps that small. Smallest I have is a T3 40 trim. My calcs show my 1.8L off the chart of a T3-40 by 5500 RPM. and 206 HP @ 12 PSI. I'm not sure where a T25 falls when you factor trims, or if there are any. I would assume there are.

I have an sr20 T25 as well. I believe it's from a S13. I measured the wheels when i rebuilt it, exactly the same size as the GT2554 except journal bearing. You could measure the wheels then go to turbobygarrett.com and see if it's close to matching any of those turbos. If you find a match I think it's safe to assume the compressor maps would be similiar.