- Compressing air adds
- The less heat added
during boost, the more efficient the compressor.
- The higher the boost, the more heat
is injected, the lower the efficiency.
Compressing air to increase charge
density adds heat to it. The more compressed the air, the greater the heat
increase. The more efficient a compressor is the less heat it injects into the
compressed air. But all compressors inevitable inject some heat into the
This is why doubling the inlet air pressure does not necessarily double the
Because of the above, more boost will not always lead to more power. Just
because the engine is rugged enough to accept more boost doesn’t mean you should
run it at the max boost possible.
As already mentioned, increased boost means increased air temp. a point will be
reached where the ignition needs to be retarded so much that the net result of
raising boost is actually a drop in overall brake horsepower.
The problem is compounded because at higher boost, the turbos efficiency drops
below the point where the increased boost produces more power.