Thread: 2.5" vs 3"
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Old 11-13-2013, 10:33 AM   #11
ramiram1984
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Quote:
Originally Posted by ecko04 View Post
It's all good. 2.5", 2.75" and 3" have been discussed pretty extensively.

In a nutshell, for the NA vehicle 2.5" is fine.

Any form of FI will benefit from larger diameter piping.

If I were even thinking about FI, I would go with 3" or at the minimum a 2.5" overpipe, larger and less restrictive front pipe and a 3" catback section.

Then it's a matter of what sound you like.

The benefit of larger diameter piping with a FI setup is that you're adding more exhaust gas and it needs to go somewhere. The larger piping keeps excessive exhaust gas temps down and will build boost, on a turbocharged setup, quicker than smaller diameter piping. There may be some weight savings as well. Oh...and it sounds cool.
The only thing that confuses me is that, yes the diameter is larger so exhaust can flow better.
But what about where it leaves from? The diameter of that is still smaller than the larger piping header if you have one. So, the exhaust must just bottle neck somehow, no matter if it's FI or not.

This is the only thing that confuses me.
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