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The degree of exhaust expansion as it passes through
the turbine.
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The turbine flow is also
corrected for temperature and pressure at the turbine inlet (exhaust
manifold).
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Ratio of ABSOLUTE outlet pressure divided by ABSOLUTE
inlet pressure. |
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Represents the
corrected mass flow rate of air, taking into account air density
(ambient temperature and pressure). |
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The efficiency contours depict the regional
efficiency of the compressor set. This efficiency is simply the
percentage of turbo shaft power that converts to actual air
compression. When sizing a turbo, it is important to maintain the
proposed lugline with a high efficiency range on the map. |
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The surge region, located on the left-hand side
of the compressor map, is an area of flow instability typically
caused by compressor inducer stall. The turbo should be sized so
that the engine does not operate in the surge range. When
turbochargers operate in surge for long periods of time, bearing
failures may occur. |
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The choke line is on the right hand side of the
compressor map and represents the flow limit. When a turbocharger is
run deep into choke, turbo speeds will increase dramatically while
compressor efficiency will plunge (very high compressor outlet
temps), and turbo durability will be compromised. |
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