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How to read a turbine flow map?

Discussion pertaining to positive pressure E28s.
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turbodan
Posts: 9246
Joined: Jan 09, 2007 10:19 PM

How to read a turbine flow map?

Post by turbodan »

I'm clear on compression maps, but I dont really know what to make of turbine flow maps. The red line on this one represents the hot side of the turbocharger on my 528:
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The way I'm reading it, this turbine can flow a maximum of ~21 pounds of air a minute, and it reaches that at a pressure ratio of 2.5. I suppose the rest goes through the wastegate.

I'm entertaining the thought of a GT3582R with either a .86 or 1.06 turbine housing:
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Garrett recommends the 3582 for applications making 400-600 HP. Oddly enough, the .63 AR housing only flows two or three pounds/min more than my .86 AR 2871. It seems like that would be a major mismatch. If you're forcing 50 lbs/min in and the turbine maxes out at 23 lbs/min, there would be more exhaust flowing through the wastegate than the turbine itself, right?

Looking at the flow maps for the 3582, it makes the 2871 .86 seem relatively free flowing on the turbine side for a compressor that peaks around 45lbs/min.
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