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3" or 4" cai

 
Old 12-19-2011, 08:12 AM
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Default 3" or 4" cai

I have enough tubing in both sizes to make a cai. I have an aem standalone that's going on the car and making a custom 3" exhaust. Would I see more power gains with the 4" or would the stock tv heads cams etc not be able to move that amount of air?
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Old 12-19-2011, 12:14 PM
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Going from a larger pipe to a smaller pipe will help. You can even use and should use a velocity stack to help the air flow. I found this one that has a good outer ring to mount the filter on, but there are cheaper ones out there.
http://www.turbohoses.com/velocity_stack.htm
I would not use a smaller pipe than the i.d. of the T/B for the pipe that mounts to the T/B

ROD
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Old 12-19-2011, 12:32 PM
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It seems that 3.5" intakes don't do well at all on the F20/22. I'd imagine that a 4" would do worse. Stay with a 3" or have a 3.5" into 3".
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Old 12-19-2011, 12:50 PM
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Where have you seen that? I've read and seen dyno graphs that state the complete opposite.

No offense to anyone but if you don't have any proof to back up what you're saying don't post.
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Old 12-19-2011, 01:01 PM
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Brian just tested it. He was nice enough to give me the results but I don't believe he posted it up yet. He's running a 3" into 3.5".
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Old 12-19-2011, 03:17 PM
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Mods? Standalone?

This guy tested multiple setups and his 3.5" is proven to gain more power. https://www.s2ki.com/s2000/topic/909...tepped-intake/

The AEM intake is even a 3.5" to 3"


Im going with the 4" with velocity stack, tapered right before the tb. Might get a bigger throttle body too. I'll post numbers when I get back from vacation.
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Old 12-19-2011, 04:18 PM
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i'm running a stepped intake. the car h22tof22 is talking about was using a straight 3.5 inch intake pipe with no step.
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Old 12-19-2011, 04:33 PM
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Originally Posted by b.r.i.a.n. View Post
i'm running a stepped intake. the car h22tof22 is talking about was using a straight 3.5 inch intake pipe with no step.
Lol the link I posted was to your posts, what're your thought on doing the 4"? Im pretty much doing your build, until I feel like buying a turbo and building a mani.
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Old 12-19-2011, 05:03 PM
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Originally Posted by Dude_Man View Post
Lol the link I posted was to your posts, what're your thought on doing the 4"? Im pretty much doing your build, until I feel like buying a turbo and building a mani.
on a stock longblock i would say it's overkill. if you choose to test a 4 inch intake pipe, make it stepped. 4 inch tapering down to 3.5 inch.
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Old 12-19-2011, 05:22 PM
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My car and a couple of other s2k's I have dyno'd had very large gains going from a 3 inch cai to a 4inch.

once you start making more than 220hp to the tires a 3 inch intake is simply not big enough. Its way easier to hurt power with an intake thats too small rather than one thats too big.

Also, the air filter makes a difference. AEM dryflow always makes a couple more hp than anything else on the market.
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