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06 gxp custom cai

If I were doing a FWI like yourse, I would use:

Throttlebody > 3" to 4" adapter > 4" bend> 4" to 3" adapter > MAF > 3" to 4" adapter > 4" straight pipe > 4" adapter > 4" bend > 4"-opening filter

Optimally all bends should be 4". A 4" 90* bend has roughly the same properties as 3" straight pipe. Obviously, the ~22.5* bend off the throttlebody and the 45* (is that 45*?) bend at the filter only equal 67.5* total bend, but there's no reason to do anything but 4".
 
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As for the 4" pipe, its all about volume. The larger intake pipe essentially acts as like a surge tank. With 3" its just keeping up, with 4" there is excess air there to keep the flow at max.
 
stealthee said:
As for the 4" pipe, its all about volume. The larger intake pipe essentially acts as like a surge tank. With 3" its just keeping up, with 4" there is excess air there to keep the flow at max.
Click to expand...

I was 2 paragraphs into saying that when I scrolled down I saw you already said it much more simply :th_thumbsup-wink:
 
so...i tried something today. i used my buddies g-tech pro and did some runs with my FWI. i got a pretty accurate 14.51. i did this three times and got a 14.5 on all three. i took intake apart and bolted the filter back to the MAF just to see what might be happening. 3 runs on the g-tech i got 3 14.1 runs. i went home and started looking at all my pieces. it turns out that the 90 degree bend in this picture is 3 inches on each end and actually only 2.25 inches in diameter in the center. i guess i should have noticed that in the 1st place. time for more research.
20110310171751.jpg
 


f3racer said:
it turns out that the 90 degree bend in this picture is 3 inches on each end and actually only 2.25 inches in diameter in the center. i guess i should have noticed that in the 1st place. time for more research.
Click to expand...


That's why I am extremely prejudice toward hardware store intakes. I noticed this when deciding on my short ram intake.

As a side note, when making a short ram people should buy proper tubing here: Global Technology and Engineering
 
f3racer said:
i used my buddies g-tech pro and did some runs with my FWI. i got a pretty accurate 14.51. i did this three times and got a 14.5 on all three. i took intake apart and bolted the filter back to the MAF just to see what might be happening. 3 runs on the g-tech i got 3 14.1 runs.
Click to expand...


The numbers 14.5 and 14.1: Are these your Air-Fuel Ratio (AFR)?
 


f3racer said:
so...i tried something today. i used my buddies g-tech pro and did some runs with my FWI. i got a pretty accurate 14.51. i did this three times and got a 14.5 on all three. i took intake apart and bolted the filter back to the MAF just to see what might be happening. 3 runs on the g-tech i got 3 14.1 runs. i went home and started looking at all my pieces. it turns out that the 90 degree bend in this picture is 3 inches on each end and actually only 2.25 inches in diameter in the center. i guess i should have noticed that in the 1st place. time for more research.
20110310171751.jpg
Click to expand...


You need a better filter than that cheap Ebay one too. I hate sounding like a sales rep, but check out Green Filter USA. You can get a cone in almost any size you want. It outflows K&N by a ridiculous amount because of a slight design difference too.
 


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