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3" catback vs. 3" to 2 2.5" catback

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Old Nov 21, 2006 | 01:16 AM
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Default 3" catback vs. 3" to 2 2.5" catback

I've been on the fence about this for a little bit now...

the TSP Rumbler, according to TSP, is 3" intermediate and over the axle, then splits into 2 2.5" tail pipes. The SLP Loudmouth is the same.

Is there going to be a big difference in performance or sound if I were to compare that to a 3" intermediate/overaxle into a pair of 3" tail pipes in a similar design to the Rumbler/Loudmouth setup?

I know there is much more fabrication in a 3" setup vs. the 2 2.5" setup but in all honesty, is the 3" to the tips necessary?

I was really hoping to do a true 3" all the way back but lack of funds + time to do it makes it a little more difficult to want to do...

I've priced out the parts alone, and one could almost say, with the time/cost of fabricating up the 3" you could just get the GMMG and call it a day... however the only drawback IMO of the GMMG is that there are far too many bends and I'd like to somewhat simplify it.

anyone have any thoughts on that?
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Old Nov 21, 2006 | 02:56 AM
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IT is not necessary. You aren't laying down the power that is going to over bear a 2.5" setup over the axle. I run 2.5" from the collectors back. Put down 421/379 with it. I think that it works well.
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Old Nov 21, 2006 | 10:47 AM
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Originally Posted by orangeapeel
IT is not necessary. You aren't laying down the power that is going to over bear a 2.5" setup over the axle. I run 2.5" from the collectors back. Put down 421/379 with it. I think that it works well.
yeah but I'm not doing a dual system :o
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Old Nov 21, 2006 | 11:01 AM
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your splitting peas. It won't make a different. If it did, it would probably be .1 hp, which coudl be blamed on a bunch of other things.
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Old Nov 21, 2006 | 11:13 AM
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Originally Posted by BrandonDrecksage
your splitting peas. It won't make a different. If it did, it would probably be .1 hp, which coudl be blamed on a bunch of other things.
i'm not really splitting peas I'm just trying to figure out what is best in the long run.

I probably won't ever go true duals unless its over the axle, at the moment, the 3" into 2 2.5" seems the easiest and cheapest, however, will it be worth it in the long run as far as overall flow and performance and holding up to various modifications over the months and years
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Old Nov 21, 2006 | 12:55 PM
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If you are going to make big power and stay with a Y-Pipe, you should be 3" collectors into 3.5" Intermediate pipe. Take that over the axle and then go back into your 3" split. If you're planning to lay down 500 rwhp, the bigger bottleneck is the 3" I-pipe, not that it is twin 2.5" post axle .

The alternative is to use a cut out. I had a 3.5" I-Pipe with a cutout before the axle. It then necked down to 3" to go my SLP D/D. When I needed every last HP, the cut-out was open.
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Old Nov 21, 2006 | 09:52 PM
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Originally Posted by Demon Of Dreams
i'm not really splitting peas I'm just trying to figure out what is best in the long run.

I probably won't ever go true duals unless its over the axle, at the moment, the 3" into 2 2.5" seems the easiest and cheapest, however, will it be worth it in the long run as far as overall flow and performance and holding up to various modifications over the months and years
yes, you are splitting peas asking which is better between 3 inch of splitn into two 2.5 inch after the axle! Now if you were talking true duals 3 inch vs 2.5, different story.
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Old Nov 22, 2006 | 05:52 AM
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Originally Posted by BrandonDrecksage
yes, you are splitting peas asking which is better between 3 inch of splitn into two 2.5 inch after the axle! Now if you were talking true duals 3 inch vs 2.5, different story.
Even then. Dual 2.5in pipe should flow as much if not more then a single 5 inch pipe and you'd better have a hell of a motor to outflow that ****!
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Old Nov 22, 2006 | 02:50 PM
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Originally Posted by Justin00SS
Even then. Dual 2.5in pipe should flow as much if not more then a single 5 inch pipe and you'd better have a hell of a motor to outflow that ****!
Just not to confuse anyone, the cross section of a pipe is Pi*r^2, so 5" will outflow twin 2.5" pipes by a huge amount, not to mention friction and pressure issues with a smaller pipe. The point being, this is why a well designed 3" into 3.5" Y-Pipe & 3.5" I-pipe with a cutout can handle a ton of HP.
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Old Nov 22, 2006 | 03:00 PM
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Just run bullets off the headers
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Old Nov 22, 2006 | 03:50 PM
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Ragtop I need to ask you this. I have just received my pacesetters, cats, and a flowmaster merge that is the same size you have been speaking of. Dual 3" in and 3.5" out but is it too large of a diameter if this is going to be my first performance upgrade? I asked in another thread and had no response.
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