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Old 11-19-2009, 12:46 PM   #1
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Default 2" or 2.5" IC pipes?

Everyone keeps yelling at me about my starion IC, so I'm going to replace it with a big son of a bitch( more money, more weight, pointless) well I really don't care, I like them big <~~~ that was for the next comment you guys will say. Anyways the question is should I go with 2" or 2.5" IC pipes? Is there an avantage? Let me know your opinions
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Old 11-19-2009, 12:48 PM   #2
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2" hot side, 2.5" cold side is the norm.
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Old 11-19-2009, 12:55 PM   #3
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That's what I have now but I rather just order pipes all one size since it will be cheaper then two different ones
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Old 11-19-2009, 12:55 PM   #4
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Quote:
Originally Posted by miataspeed2005 View Post
I really don't care, I like them big
... nothing I say here will be clever enough to make it worth it... I'll leave this one to someone else

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Originally Posted by miataspeed2005
Anyways the question is should I go with 2" or 2.5" IC pipes? Is there an avantage? Let me know your opinions
Thanks
Your Dad
I'm not an engineer, but its my understanding that smaller pipes = less volume = faster boost response. However, being able to flow less volume, you sacrifice top end power. It is also *slightly* tougher to route 2.5" pipes on the hot side depending on which way you go, whether you still have ac/ps, and how your compressor housing is oriented. I went with 2.5", but my engine bay is super gutted. I've also seen guys do 2" on the hot side, and 2.5" on the cold side. It's really about personal preference and what you have to work with.


ps. sorry if this wasn't much help.
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Old 11-19-2009, 12:57 PM   #5
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However, being able to flow less volume, you sacrifice top end power.

And that's only if he happens to be flowing more than the pipes can allow for, which I doubt is happening anytime soon.
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Old 11-19-2009, 01:25 PM   #6
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But isn't the flow of air that goes through my IC the same as the flow going thru my exhaust? And if people run 3" exhaust would you really wanna run 2" pipe?
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Old 11-19-2009, 01:45 PM   #7
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No, it's the same as the flow rate through your turbine.

We run larger exhaust to maximize the pressure differential across the turbine.

EDIT:

My BEGi kit uses 1.75" hot and cold side, which I'm sure gives me quite a bit of velocity. Since upgrading to COPS and 2.5" exhaust I haven't seen any drop in power at the big end. I'm only flowing ~80% what you're flowing though.
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Old 11-19-2009, 01:55 PM   #8
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Well my biggest consern was my top end power and torque. If you saw my dyno graph you could see my topend. One I'm leaning out the fuel from 6k on, two I'm upgrading my wastegate and re routing it to my IC cold side, and three 2.5" IC pipes(well maybe that's why I mad a thread)
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Old 11-19-2009, 02:04 PM   #9
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You'd be surprised how much a little tuning and simple upgrades can really make some pull at the top end.

I had a thread not too long ago about how to augment the big end since I'm boost limited with this turbo. A few posts in my build thread explain how that problem went away...basically the two mods I mentioned above.

I seriously doubt that 2" piping would limit you...but I haven't done the math. I can tell you that the difference in flow capacity between 2" and 2.5" inch will be significant (~60%) if you want to plan ahead for future upgrades or just be sure now. The trade offs are probably unnoticeable to the butt dyno at your current power level.

I do know that I wouldn't hook up a 2.5" adapter to any compressor outlet less than 2" in diameter. You want to keep pressure drop to a minimum pre-intercooler. This is why 2" hot/2.5" cold is commonly accepted like levnubbin said. Once the air is cooled you can expand it with minimal deltaT, and you have to step up to 2.5" sometime before you hit the throttle body anyhow.
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Old 11-19-2009, 02:12 PM   #10
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But isn't the flow of air that goes through my IC the same as the flow going thru my exhaust? And if people run 3" exhaust would you really wanna run 2" pipe?
The mass exiting your tailpipe is roughly the mass of air coming in through your IC piping plus another ~7-9% for the mass of injected fuel.

But that mass going into your cylinders gets heated up a whole bunch during combustion, causing it to expand. Ideal gas law says PV=nRT. The increase in temp causes the increase in volume that requires your exhaust piping to be bigger than your intake to flow the same mass without creating a restriction.
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Old 11-19-2009, 02:28 PM   #11
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So I think I'm just going to order the IC first then see how much pipe I need to finish it off. Sounds like 2" hot and 2.5" cold like I had in the first place is the way to go
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Old 11-19-2009, 03:02 PM   #12
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Do you guys think I'll reach the 250hp with those 3 things I mentioned? 17hp doesn't seem too hard to acomplish
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Old 11-19-2009, 03:08 PM   #13
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A better waste gate and tune will get you there. Unless you're IAT's are high I wouldn't mess with the IC setup at all. Unless you're doing it for aesthetics.
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Old 11-19-2009, 03:13 PM   #14
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Quote:
Unless you're doing it for aesthetics.
if that was the case this thread would be about getting a new bumper cover.

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Old 11-19-2009, 03:20 PM   #15
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if that was the case this thread would be about getting a new bumper cover.

lmao zingerrrr!
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Old 11-19-2009, 03:57 PM   #16
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you both need one!
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Old 11-19-2009, 04:31 PM   #17
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if that was the case this thread would be about getting a new bumper cover.

I hate you
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Old 11-19-2009, 04:37 PM   #18
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you know you lol'd.
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Old 11-19-2009, 07:23 PM   #19
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Measure your turbo outlet ID and match the hot to that...

Last edited by triple88a; 11-19-2009 at 07:40 PM.
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Old 11-19-2009, 07:28 PM   #20
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i run 2 1/4" IC pipes all the way around =o
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