That's how surge is eliminated: Less airflow at relatively low compressor wheel speeds. By looking at a compressor efficiency map, the surge line is on the far left of the "island" where the pressure ratio is too high for the actual airflow through the compressor. In simpler terms, the boost is too high for the actual amount of airflow through the engine and the compressor flow comes way out of it's efficiency range.
A ported compressor housing (such as the ATS unit) also slightly lowers flow.
The noise is simply a function of the impeller design. The staggered-height vanes aren't as "clean" as the standard 99.5-03 impellers as far as chopping up the air is concerned.
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Tuning, PCM flashing, and burning chips for 7.3s since 2008. Repairing all aspects of 7.3L Powerstrokes for 25 years.
Eight 7.3L PSDs in the driveway including a 1994 Crown Vic and 1973 F100/2002 F350. Looking for the next victim.
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Mon, March 22nd, 2010, 03:01 PM
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