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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,034
That's a lot of engine with a turbocharger!
Key to turbo header design is velocity. Counter intuitive to normally aspirated builds, the flow must restrict as it makes its way to the turbine which increases its speed. The exhaust ports you site at 44.5mm are huge. Piping with this ID would be 1 7/8"OD. Decision on primary and secondary size depends on projected HP output at X000rpm at x.xbar boost. That is the first question that needs to be answered. How the car will be used, where the powerband is preferred, and specifics on the turbo specifications also will be needed information.
My starting point would be 5th harmonic equal length 1.75"OD bumped primaries and equal length 2.25" secondaries (the secondaries on the set you have pictured are too long) to improve off boost performance and torque. Split volute T4 flange with twin waste gates.

RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 02-12-2019, 11:14 AM
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