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MikeD930 MikeD930 is offline
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Join Date: Apr 2008
Location: missouri
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I'm not an expert in turbo graphs but as you can see the graph on the left has more effeciency range (i.e. fatter area within the curves). Also, surge happens when the turbo operates to the left of the most left curve. So, the surge is less likely to happen on the left graph at the same air flow for a given pressure ratio. This can happen when the turbo is too large for a given engine dispacement under certain condition such as when the turbo starts to build boost at low engine rpm creating a phenomena where more boost builds than the engine can ingest. I'm sure this happens rarely on our 930 since our engine is relatively large for typical turbos used on these cars. I hope my lame explanation helps.
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MikeD
'87 930
Old 06-22-2011, 02:52 AM
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