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Old 04-13-2004, 01:56 PM   #1
HOK
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Default 3 Inch IC piping too big?

I'm putting on my front mount and I have 2.5 inches from the turbo to the IC and then 3 inch from the IC to the TB...

Is this too big ? what you guys think?
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Old 04-13-2004, 02:15 PM   #2
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Personally, I think it's too big. I would think that since the charge air was just cooled and made more dense, it's velocity would be even less and create more lag. There is a possibility, though, that the larger diameter out piping of the IC will cause the air to flow through it more smoothly/slowly and provide better cooling, though.
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Old 04-13-2004, 02:40 PM   #3
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id probably keep it the same throughout it, but i dont kno wmuch bout flow
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Old 04-13-2004, 11:49 PM   #4
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good luck plumbing 3" piping... its fricken huge and wont likely fit through there.

-Jake
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Old 04-14-2004, 12:07 AM   #5
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already did... hehehe

But I'm still afraid it won't spool...
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Old 04-14-2004, 01:33 AM   #6
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Check what the other FMIC's are running for WRX's and such, they tend to run closer to 2"-2.25", not any 3" piping. That will have major lag.
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Old 04-14-2004, 02:12 AM   #7
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id say on a setup making a good amount of power, 2.25 into the IC, 2.5 out (at most 2.75)
I need to upgrade
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Old 04-14-2004, 11:03 AM   #8
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mmm I do know that most other subarus have 2.25 .5 inch piping, but has anyone tried 3 inch? Well we are half done anyways... but then it snows... can you beleive this... Mid april and 2 days ago it was 20 C and now its snowing

the drag track was going to open this friday... i guess not now...

Any fluid / flow dynamic gurus out there? One of the reasons I did this was the size of the TB is very close to 3 inch, 73 mm?? No restriction
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Old 04-15-2004, 06:48 PM   #9
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3" seems a bit big. I know that most of the DSM guys with very hardcore setups are running 2.5" piping.

I would think that the place to have the 3" piping would be from the turbo to intercooler as the air is way hotter then and therefore displacing a greater volume. Then do like 2.75 or 2.5" piping to the TB.

Sounds like you have it mostly done though, so do some testing and see how it is. Do you have any data for smaller piping setups?
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Old 04-15-2004, 10:20 PM   #10
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3" is way too big, you will probably be able to flow ALOT of air (I sure hope you are shooting for at least 20lbs of boost) but will probably be down on quite a bit of torque due to the total lack of any real flow velocity.... it should do OK if you have no problems with a super laggy drag racer but you should find a way to step down a bit.... using the larger piping at the turbo outlet would have been much better. I wish I could give you some specific numbers but gas flow involves some really really scary math... I quit my desire to be a mechanical engineer once I hit that stuff.

*edit*
if you want to run any numbers yourself here is where you can get the info

http://www.lmnoeng.com/Flow/bernoulli.htm

but remember, your total flow area will go up with a square of diameter, but your flow velocity will drop at close to that same square rate, just remember, people much smarter than I are building supras in quad digit horsepower and torque figures using 3" charge piping.... so it's pretty overkill

Last edited by no-coast-punk; 04-15-2004 at 10:26 PM.
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Old 04-15-2004, 11:09 PM   #11
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Works fine for my setup. No lag and lots of cool air.
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Old 04-15-2004, 11:22 PM   #12
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Yes yes.. i have succumb to the losing too much velocity.... theory....

That link is pretty good... what happened was as i sat there looking at the piping I figured that if a Rally car can pump out 300 + with a tiny tiny 1.5 inch restrictor or whatever I should be able to do 300whp with 2.5 inches heh... I believe that the 3 inches won't make THAT big a difference between 2.5 I would say... i will be making a final decision this weekend when we are building the car...

But err.. SUbafastR you have 3 inch Intercooler piping???!!?

I was debating that with that large a IC piping i need a 2.5 or 2.25 uppipe... any pics?
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Old 04-16-2004, 12:16 AM   #13
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Turbo restrictors sit before the turbo inlet so the turbo is sucking through the restrictor, this gives the air stream a TON of velocity which is how they are able to pull 500+ lbs of torque out of a 2 liter motor... but the torque peak is at like 3000 RPM's and the motor totally chokes out above anything like 4500. The key to developing power is to maintain a certain pressure (flow velocity and flow area) within your intake plenum (technically your intake piping is part of the plenum) too much pressure and you will see rally car like torque curves, too little and you will see some crazy top end power without much torque (such as your typical honda motor). This is why just about every company out there has played around with variable geometry plenums to keep that pressure in an ideal range, problem is you either have to make such a system huge, or restrictive with lots of turbulence. I dunno, it's late and I'm tired and rambling alot, just keep in mind that your intake assembly can greatly affect how your motor behaves, it depends what your goals are with the car, if you really are shooting for nothing but a straight line creature.... piping that size might not be all that bad, as long as you do what others have said and use larger piping as close to the turbo as possible to take advantage of the hot air trying to move faster. sorry if this last post didn't make much sense
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Old 04-20-2004, 01:58 PM   #14
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The intercooler's inlet and outlet where 3", so I figured I'd just keep it that size on the exit.
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Old 04-20-2004, 03:39 PM   #15
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wow that is the same way I was going to do my piping!!! how is it working?
Thanks, Micah
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Old 04-20-2004, 03:48 PM   #16
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Well, I make more power than the top mount and there is no extra lag at all!
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Old 04-20-2004, 03:54 PM   #17
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is that a TD04 turbo?...how hard/easy was it to spin it...any drilling needed to re-mount the wastegate?
Thanks, Micah
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Old 04-20-2004, 05:13 PM   #18
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Quote:
Originally posted by SubaFastR
Well, I make more power than the top mount and there is no extra lag at all!
I guess copying my piping route worked out for ya?
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Old 04-20-2004, 07:53 PM   #19
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What are you smoking monkey boy? Your piping looks nothing like mine. Lay off the bananas.
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Old 04-20-2004, 07:55 PM   #20
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Quote:
Originally posted by SubaFastR
What are you smoking monkey boy? Your piping looks nothing like mine. Lay off the bananas.
thats cute, remember, you had your piping routed exactly like mine?
but thats cool, must be nice to go full throttle all day and not exceed the speed limit

edit: cus Im not THAT mean
lol
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Old 04-20-2004, 08:00 PM   #21
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Quote:
Originally posted by Homemade WRX
is that a TD04 turbo?...how hard/easy was it to spin it...any drilling needed to re-mount the wastegate?
Thanks, Micah
It's actually the VF39. It was really easy to clock, but it is not the same story with a stock WRX turbo. I did drill one hole in the wastegate mounting plate.
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Old 04-20-2004, 08:04 PM   #22
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Quote:
Originally posted by kaos200
thats cute, remember, you had your piping routed exactly like mine?
but thats cool, must be nice to go full throttle all day and not exceed the speed limit

edit: cus Im not THAT mean
lol
Your intercooler is half the size of mine and has it's pipes routed to the middle of the core while mine are at the top. You have your turbo in a completely different spot. So, having the pipes go beside the radiator is copying? Whatever... you bought your entire intercooler setup from Don. I made mine by myself in my garage.
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Old 04-20-2004, 08:19 PM   #23
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whatever you say Kevin
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Old 04-20-2004, 08:26 PM   #24
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oh well....back to the subject....if it makes you feel any better I thought of running it that way without anyone's input...I'm others have done it
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Old 04-20-2004, 08:48 PM   #25
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Air conditioning is out if you do it this way. I found a way to get it back and will work on it once it is hotter.
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