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OPEN Crossover use DIVIDED 1.24AR, or OPEN .96AR?

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Old Jun 12, 2020 | 09:26 AM
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Question OPEN Crossover use DIVIDED 1.24AR, or OPEN .96AR?

No desire to reconfigure my OPEN T-4 flanged crossover piping.

4000# car, 370ci, currently with 78/75 .96ar cast wheel Chinese (VS Racing) turbo...4" inlet, 2.5" outlet, 3" V band exhaust
Went 9.94@138 in the heat, and was 143 mph before I let off the gas, according to logs, so it seems to be making steady power.
Regardless,
Thinking of getting a new Next Gen Billet VS Racing turbo...as I found them to be on sale.
It's also a 78/75, but has 4" inlet, 3" outlet, 4" V band exhaust
It also has choice of .96 ar OPEN flange, or 1.25 ar DIVIDED flange.

Why would/should I choose one or the other flange options?

Like I said, I have no desire to change my crossover, BUT I did want to "probably" go with a 4" OPEN fender exit PIPE next Summer.
Currently, the 3" V band connects to 3" downpipe, with cutout down just beyond the starter, and without a doubt, runs MUCH better with the cutout open.
For now, I thought I could use a 3-2.5" adapter for the compressor outlet to intercooler piping connection (an easy mod), and 4" - 3" V Band adapter (a little snug on space, but should be fine)...

I just do not know which AR will be best for me...honestly don't know much about that part of the turbo spec stuff, lol

Car makes 4-5# of boost on transbrake at 3000rpm, (in roughly 3 seconds) and although shifted at 6000-6200, it traps at 6800-6900, with no signs of being held back, or corked up...

Any input appreciated...
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Old Jun 12, 2020 | 12:54 PM
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If dead set on that turbo I would go with the open flange, I believe once you factor in the divided housing the a/r ratio isn't that much difference. I will say I recently ran my car without my full exhaust dual 3" to bullet mufflers, tailpipes, just open downpipes and made a huge difference.
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Old Jun 12, 2020 | 01:27 PM
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Originally Posted by 973800CamaroRS
If dead set on that turbo I would go with the open flange, I believe once you factor in the divided housing the a/r ratio isn't that much difference. I will say I recently ran my car without my full exhaust dual 3" to bullet mufflers, tailpipes, just open downpipes and made a huge difference.
Yeah, mine will make a steady 5# of boost, at it's low setting, with exhaust closed up, but with the same boost controller setting, and open cutout, it will make a steady rising 5-10#, and reacts/spools a lot quicker as well.
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Old Jun 12, 2020 | 04:32 PM
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The Next gen 7875 1.25 ar divided housing makes 100 ish more than the .96 ar gen 1
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Old Jun 12, 2020 | 04:43 PM
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Originally Posted by Mavn
The Next gen 7875 1.25 ar divided housing makes 100 ish more than the .96 ar gen 1
I wonder what the hp difference is .96 vs. .96?
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