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CAI tubing length

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Old Oct 23, 2007 | 07:25 PM
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Default CAI tubing length

How would you determine the ideal length & diameter tubing for a custom CAI for LS2? Would you assume the factory setup was ideal or is there a calculation that you can run to determine what is optimal?

I am trying to run one on my TBSS, but I'm concerned that the pipe diameter and or length will ultimately hamper performance.

If you were able to design a "ram air" intake how would you factor the ram effect into this equation (ie is there a forumla for speed x intake diameter x some coeffiecient=ram effect (cfm) or something like that?

Its been a long time since physics and my knowledge ran out a long time ago.
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Old Oct 23, 2007 | 09:07 PM
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You're trying to make something simple overly complicated! Go with a 4" tube and call it good!
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Old Oct 23, 2007 | 09:11 PM
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thats what i was thinking. as long as its not toooo small it should be perfectly fine. People put free flowing intakes on other wise stock cars all the time.
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Old Oct 23, 2007 | 10:01 PM
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Originally Posted by John B
You're trying to make something simple overly complicated! Go with a 4" tube and call it good!
Already done the 4". My point is how do you know "its good". Did you dyno it before and after. I try to never do something "just because". If you don't know all the reasoning behind you may be actually hurting something, in this case performance.

Now I don't think I am, but there are calculcations to stuff like this. That's how manufacturers like GM, K&N etc arrive at the dimisions for their products. Just wondering if anyone on here know's anything about it.
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Old Oct 23, 2007 | 10:29 PM
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i learned about this in school. im not sure which way affects what, but length and diameter of the intake between the throttle body and filter will affect performance. thats why you see tuned intakes for sale in the aftermarket.
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Old Oct 23, 2007 | 10:47 PM
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Originally Posted by pharmd
...there are calculcations to stuff like this. That's how manufacturers like GM, K&N etc arrive at the dimisions for their products.
Air intake design involves sophisticated calculations at General Electric’s jet engine division but probably not at General Motors. Auto engineers and stylists fight over every cubic centimeter of underhood space. In these fights, the air intake designers have very little clout. Air intake designers guess and test. They are allowed more space only if they can prove that what they have been given is impossibly inadequate.

Last edited by Gary Z; Oct 23, 2007 at 11:21 PM.
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Old Oct 23, 2007 | 11:09 PM
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Wow, I get the point about calculations, however, you missed my point......unless your motor is making mega-HP I can't imagine a 4" tube not being able to flow enough air for your average less than 800HP motor!

If you insist on this type of calculation (which isn't need for a street driven vehicle with a 4" tube) then I would re-post this in the advanced tech forum.
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Old Oct 24, 2007 | 08:15 AM
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Ok guys if it was a perfect world CAI's would be tuned just like a LT equal length header is. But you run into the same problems with fitment. Just remember it is not just about how much it flows you also need to get the air velocity up this will help your torque numbers. A velocity stack is something you should look into putting in your CAI this is going to help you more then worrying about length and diameter. I would say anything from 3.5"-4" will work fine. I have a custom 4" intake on my LS1 RX7 with a custom mounted LS7 MAF in that 4" pipe.
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Old Oct 24, 2007 | 08:21 AM
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Honestly, more value is placed at the OEM on reducing intake NOISE than boosting HP.

Make the intake as straight of a shot going into the TB as you can and call it a day. Honestly you could spend 5 million engineering this piece and you probably wouldn't gain 3 hp over the above method^^^^
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