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do you think either or these 2 setups would work well as a custom x pipe. no mufflers being used, just straight pipe. sorry for the absolutely horrible artistic skills, but thats after a few attempts, and its my best. :dunno:


here are the designs (i know its small, the 2.5 and 3 refer to diamater size of the pipes. please note that respectfully, the designs are not model scale or angles.








hopefully somebody can give me some insight on this, as the truck is in the muffler shop awaiting labor to be done first thing in the morning. the dyno guy thinks it will work well. (the picture on the left), but i just stumbled upon some more knowledge, and iam thinking that the one on the right will work better. thanks alot

Edited by vtodd82 (see edit history)
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With the 2.5" in you have effective flow area of 9.8125 sq. in (2 pipes @ 2.5") dumped into a 7.065 sq. in (3 in center pipe) effective area. Then if you go with the 2.5" out you step back up to 9.8125 sq in. If you go with the 3" at the outlet you will get 14.13 sq in. You should get better flow with the 3" tubes out since the effective flow area is almost 4.5 sq in or 44% increase in flow area. Dylan should be right on this. The only restriction you will create (other than the natural flow in pipe restriction) will be where the 2.5" tubes drop into the 3" tube.

Edited by jboyd2004 (see edit history)
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The reason we have two different size pipes is because of the single exit. The head pipes in our two into one system are 2.5" and the tailpipe of 3 or 3.5, and generally flow the same cfm. If you put large head pipes and step down into a smaller tailpipe you will restrict flow , but increase velocity.

Velocity in a exhaust system keeps the pipes dry and prevents corrosion, Volume (larger pipe) increases cfm capacity, and runs cooler. Heat in the exhaust system is a good thing, it aids scavenging, or gets the gasses out quicker.

From an efficiency standpoint, our system is ideal for our engines power output and rpm range, plus reduces weight over true dual systems, but the main reason it's like that is reduced costs to GM and it is easier to package under the truck. One system works for many different trucks. Just the muffler is changed.

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2.5" all the way back should be plenty for our trucks unless you want to HEAVILY modify it. also a 2.5" X-pipe isn't 2.5" in the middle it's bigger, but I don't know the exact size. anyway a 3" X pipe with 2.5" on each side is not going to help over a 2.5" X. I wouldn't switch them back and forth like you are. go ALL 3" or ALL 2.5"

Edited by 383ss (see edit history)
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