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WERK I WERK I is offline
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Join Date: Jan 2003
Location: Wisconsin
Posts: 3,291
Originally Posted by beepbeep View Post
As always, devil is in the details. If you read the map above, it looks like ported shroud indeed gives better efficiency on boost threshold. But if you peek further, you see that shroud will actually give higher boost threshold (worse response) at low loads and boosts up to 1.2 bar (!). Once you start hitting 1.6 bar (which you probably never will in 930), ported shroud starts to shine.

Thus, ported shroud isn't always better. It depends on application. It's mostly used on very high boost diesel applications. But for moderate boost, it might actually make things worse.

Compressor map is needed in order to chose optimal turbocharger. Just drilling holes without actual map can easily make things worse.
Thanks for your invaluable input. What I'm most concerned about regards to shrouding are the benefits of such a design when the throttle body is suddenly closed under full boost (i.e. changing gears).
Does a design such as shrouding help reduce those stresses on the turbo?

'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 11-07-2009, 06:05 AM
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