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anthonimartini
Joined: 17 Feb 2020 Posts: 240 Location: portland oregon
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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Posted: Sat Jan 08, 2022 3:46 pm Post subject: |
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Wow! _________________ 80 Turbo - Slightly Modified |
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Cedric
Joined: 27 Aug 2004 Posts: 2614 Location: Sweden
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Posted: Sat Jan 08, 2022 7:40 pm Post subject: |
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I was pretty excited until i saw the final product. A cast steel copy of the Rhd 931 manifold would be nice to have _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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Mike9311
Joined: 14 Dec 2004 Posts: 1678 Location: Chicago-ish
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Posted: Sun Jan 09, 2022 3:17 am Post subject: |
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I guess I am not the only one scanning these things
_________________ 1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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gegge
Joined: 27 Jul 2007 Posts: 1124 Location: Sweden
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Posted: Tue Jan 11, 2022 10:00 pm Post subject: |
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A simple log is far from "optimized design"
That is inferiour to the cast OEM manifold I am afraid. _________________ Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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Cedric
Joined: 27 Aug 2004 Posts: 2614 Location: Sweden
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Posted: Tue Jan 11, 2022 11:30 pm Post subject: |
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gegge wrote: | A simple log is far from "optimized design"
That is inferiour to the cast OEM manifold I am afraid. |
the standard manifold surely has a better design for a log manfiold with smoother bends. However according to my GT power calculations the RHD manifold have better cylinder balance when the WG opens, and would be better for knock mitigation on cylinder 4. _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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Beartooth
Joined: 05 Apr 2022 Posts: 212 Location: Roberts, MT
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Posted: Thu Oct 13, 2022 7:46 am Post subject: |
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I've been paging through Corky Bell's book on turbocharging, and in the section on exhaust manifolds/headers, he states that a simple log manifold with the turbo on one end and the wastegate on the other is sub-optimal. I'm not sure if there's an issue with efficiency, if it might feed the turbine with enough exhaust to overboost even with the wastegate open, or what, but I was a little disappointed when I saw what I thought was that type of standard log manifold on my 931. After I got it off, I realized it's not like that; there's a separate passage running most of the length of the manifold from near the turbo flange back to the wastegate outlet. Again, I don't fully understand if it's a necessary element, necessary only in some cases, or just nice to have, but it was important enough for Porsche to put in the effort to incorporate.
Anyway, I know this is from a few months back, and I applaud the effort somebody put in, but I'd only consider the manifold in question if I couldn't get my hands on an original cast manifold. And if I were to run it, I'd do a number of controlled test runs looking for erratic operation before I'd trust it. What would be really cool to see would be a four-into-one or 2-2-1 tube manifold, probably with the wastegate pipe picking up just behind the turbine flange and looping over the top back to the original wastegate connection. But that could be a fabrication and packaging nightmare... _________________ 1980 931 diamond in the rough |
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