__________3'' or 2.5'' for Y-pipe?_________ 
__________3'' or 2.5'' for Y-pipe?_________
Depends on the cam and power output I would think, the 2.5" might still be somewhat restrictive over a 3" if it's a really stout set up.
For a lowered car the 2.5" is always better but of course there is the potential sacrifice of power gains just to have that extra clearance.
For a lowered car the 2.5" is always better but of course there is the potential sacrifice of power gains just to have that extra clearance.
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The critical constriction of any Y-pipe is its Merge collector. Even if you decide to go with 2.5" (2.75" would be better- while 3" best), make sure you use one of these Flowmaster collectors as your merge if you're thinking of making a custom Y, or having one made for you by an exhaust shop:
They come in 2.5" in/ 3" out, 2.5" in/ 3.5" out and 3" in/4" out
I think a 2.5" Y-pipe flowing into a 2.5"/3" Y-Merge should flow decently, considering the rest of your catback will probably be 3".
They come in 2.5" in/ 3" out, 2.5" in/ 3.5" out and 3" in/4" out
I think a 2.5" Y-pipe flowing into a 2.5"/3" Y-Merge should flow decently, considering the rest of your catback will probably be 3".
Originally Posted by LS1SS4ever
Where can I buy 2.75 Y-pipe?
Look at the QTP Y pipes as well, they come with the above mentioned Flowmaster merge collector.
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Unless you're going to run a 4" I-pipe I'm not sure there'll be a benefit to a 3" Y-pipe. Now if you were talking true duals then IMO 3" is the way to go. Either way, if you do go for 3" (actually this is probably applicable to 2.5" as well) strongly consider using one of the Dr. Gas clearance tubes just behind the collector on the driver's side. You'll be surprised how much ground clearance you'll gain by doing this.
link: http://www.drgas.com/product.asp?id=10
link: http://www.drgas.com/product.asp?id=10
The point mentioned above is the one that I think needs clarified. What is the point of a 3" y-pipe only to restrict it to a 3" catback?
My thinking is this: As gases cool, they will compress, meaning that you will get the same flow out of smaller pipes. I wish that it was proven that this happens in this situation though. I think the ideal situation would be to have a 2.5" y-pipe with a 2.5in/3"out merge collector going to the 3" catback. Because two 2.5" pipes outflow one 3" pipe. Anyone care to comment on this?
My thinking is this: As gases cool, they will compress, meaning that you will get the same flow out of smaller pipes. I wish that it was proven that this happens in this situation though. I think the ideal situation would be to have a 2.5" y-pipe with a 2.5in/3"out merge collector going to the 3" catback. Because two 2.5" pipes outflow one 3" pipe. Anyone care to comment on this?
