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Originally Posted by serialk11r
That chart makes no sense, why is boost dropping off at the high end, compressor surge? Or am I missing something obvious? Is it a restrictor?
Going off the chart 60kPa max boost sounds like it will get us the ~280hp we are looking for on this car.
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I have no way of knowing 100% for sure, but it looks like the pulley test was with the same restrictor for each test (note the max power is similar, but peaks at different times). The restrictor is then the other version - same pulley, but different restrictors giving different max power.
And technically, the restrictor doesn't limit boost - it limits max horsepower. When the engine can start to 'suck' more air at higher RPM compared to what the compressor is putting out, then boost pressure goes back down.
In any forced induction application, boost is the air that didn't make it into the engine - really, boost doesn't give you horsepower, airflow does.
-Charlie