need advice on exhaust size for my longtubes need lots of opinions

[bluecmaro96]

the opening at the collector on the headers is almost 2 1/2" inside the y pipe is like 2 1/4" on the end that the two pipes go in and about 2 1/2" on the end that the cat would go on, so 2 1/4 going in 2 1/2 going out, i wanted to run 3" pipe all the way from headers back to exhaust, i would like to hear all your opinions on what size pipe to use that would give me max gains in the 1/4. starting from the size of the pipe that comes off the headers going into the y pipe and i also would like to hear the size of the pipe i should use coming out of the y pipe and going all the way back, all suggestions appreciated

[scottblack]

Did ya finally get em yet???

Since it is 2 1/2 going out, you might as well stick with either that or even go with 3 inch so the backpressure won't have a chance to bottleneck and restrict you. I'd go with 3 inch since you have that "special" motor and it needs to breathe. [img]tongue.gif[/img]

Scott

[mw02]

run open headers!

:D

[bluecmaro96]

I wouldnt call my motor special but thanks :D im pretty sure you have to have a y pipe on so it doesnt throw o2 sensor code. im not sure if i should go with a 3" y pipe or 2 1/2" y pipe.

[ April 17, 2002: Message edited by: bluecmaro96 ]</p>

[OnixV6]

i think you should go 3" from the Y collector back. like this or that, which ever fits the headers.

BTW, i'll let you know tomorrow about the 3rd gen for AIS. it's not looking good, though.

[bluecmaro96]

one is 2 1/4" imlets and the other is 2 1/2" inlets but both 3" outlets, i will use 3" from the outlet all the way back but what i need to know is will i get better results from having the pipes that come off the headers 3" or like 2 something?

[John_D.]

3" is probably overkill, unless you are going the poweradder route. As far as a 2.75 cat, I don't remember seeing any when I was shopping for mine last week, but I wasn't really looking for 2.75. You can check summitracing.com, jegs.com, and magnaflow.com for some ideas on available sizing.

If you are asking if the collectors for each header should be 3", I would say no to that. If 3" is the most you would ever need for a total of 6 cylinders worth of exhaust, then you definitely don't need that much for only one side (3 cylinders).

[OnixV6]

i just re-read your original post. from what i understand, the header collectors are 2.5" out. i think you should match it and go with 2.5" in/3"out Y-pipe. 3" off the headers will probbly not help since exhaust is still coming off the smaller 2.5" collectors.

BTW, my 3rd gen idea is a no go. couldn't find one that is road worthy. sorry.

[RacerJ]

If the headers are 2.5" going to the Y-pipe, then the Y-pipe collector/outlet should be 3". I have changed my opinion about the whole 2.5"/3" topic. Nobody start and get us off topic, but it seems that it is common opinion by most who have made the jump to 3" that there isn't a noticeable power loss. So for all intents and purposes I think it can be overlooked. But my real reason for supporting the 3" is that it's simply easier to go with. After a long ordeal with Dynomax, it seems that they no longer make or stock the mandrel bent 2.5" I-pipes. Nobody else that I know of makes them. So it's simply easier to go with the 3", because going to non-mandrel 2.5" just isn't worth anyone's time or money. (I'm fine with the 2.75" pipe too, before you ask. ;) )

Anyway, just run a 3" system and see how it goes.