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A proper X-pipe has the two pipes just kind of graze each other. This is good:
This is junk:
Actually they perform nearly identically. They have been dyno tested several times by several different people. Use the one that fits your chassis and driveline the best.
Will there be a difference? Yes. Will it be drastic enough to feel? No. To hear? Very possibly. I myself would go with the one on the right to eek out every tq/hp but there are enough X vs H soundclips on here to pick which you like better. I myself am utterly convinced (and I am in good company) that you almost never want back pressure from a power or efficiency standpoint. Especially LS and new LT engines, they want to breathe and as long as the design is good it's hard to go too big or too free flowing.
I dont have enough space for 3" catback, but i feel the 2-3/4" is the best balance between 2-1/2 and 3"
The 2.5" is great off the line, but no top end for me. So i will start wirh a 3" collector, go through cats and resonators, then tapper to 2.75" do an xpipe then tapper to 2.5" after the driveshaft carrier and keep it 2.5" all the way back.
I have the corsa Ti tailpipes, that is why the 2.5" in the rear.
Lookin for more than 500rwhp and am 20hp short.
Next venture is better sprayin inj and possible ls7 heads and intake
I'm using ARH 1 7/8" Primary to 3"collector headers (no cats or resonators) and 3" X-pipe on my G8 with 3inch going all the way back to stepped down 2.5" GXP (flow through) mufflers. There is no drone, or low frequency resonance/annoyance. This is on an LSA 6.2 setup though.
The smoothest flowing X-pipe will get you the most gains. I'm not sure the exhaust diameter change will get you where you want to go on the Top End. A different set of heads, intake manifold and cam is probably more in line to get you where you want to be. A good first step would be to measure your current airflow restrictions to get quantitative measurements pre intake and post exhaust so you can confirm you're actually helping the system when you make any of these changes. You might find that the 2.5" corsa is the ultimate restriction even if you were to go full 3" pre-catback. The upgrade from H to X will probably get you 1-4hp best case, which is imperceptible, but X-pipes typically sound a bit better so there is that advantage.
I am sportin a 416ci NA with ported ls9 haeds, 1-7/8 kook headers.
You might be right, on the 2.5 restrictin my top end...
Let me pay with the midsection in the side by side pipe.
Just need to put her on a lift so i may get started.
Will post my findings
Ls7 topend is 3k-5k depending on if i want to go ported or not. I will have to use a smaller exhaust valve as stock one will be awfully close to the cyl wall.
I am sportin a 416ci NA with ported ls9 haeds, 1-7/8 kook headers.
You might be right, on the 2.5 restrictin my top end...
Let me pay with the midsection in the side by side pipe.
Just need to put her on a lift so i may get started.
Will post my findings
Ls7 topend is 3k-5k depending on if i want to go ported or not. I will have to use a smaller exhaust valve as stock one will be awfully close to the cyl wall.
What intake manifold are you currently using? I wouldn't go the LS7 top end route on a non-LS7 block. Too many incompatabilities, not to mention like you've already stated valve clearance issues. You'd lose any advantage of LS7 heads by making the valves smaller or same size as LS3 valves to overcome the hard clearance issues.
Love to see some action in the forums! Everything is seemingly being overtaken by FB.
interested to see where this goes. I’m running LS3 top end on an LS2, mild cam, LT’s, and MF catback. I’ve contemplated the FAST + TB but not sure if my 6.0 would benefit.
It definitely would benefit, especially if a ported 102 and you retuned. It's a pricey chunk but that's the only compromise, more power and more MPGs (potentially) with no real hit to reliability.
10-18-2020, 10:02 AM
X-pipe debate 
