On the surface this sounds normal, but if you’d like TRIFECTA engineers to help you look into it more closely, please contact our support team. Some more background info:
A compressor, be it a turbocharger, or a supercharger increases intake manifold pressure on a pressure ratio basis. Consider the following:
If you’re at sea level (100kPa BARO), and, at full power, your manifold pressure maxes out at 250kPa absolute, then your turbocharger pressure ratio limit is 2.5.
If you go up to 4000 feet altitude, the barometric pressure drops to around 85kPa. Pressure ratio limit is generally fixed, so, at 2.5, your manifold pressure drops to 85 * 2.5 = 213kPa. You’ve lost about 15% of maximum power, not to mention longer spool times because the air (and, hence, your engine exhaust) is less dense.
The factory calibration addresses this to some degree by also limiting the engine power output to a level that’s lower than the maximum boost potential. On the factory calibration, if you measured boost levels at sea level vs 4000 feet, you would find they would be higher at 4000 feet, but the engine power would be the same as at sea level.
Performance calibrations aim to extract all of the performance possible out of the turbocharger regardless of altitude, so you’ll see a larger difference between power at sea level and higher altitude.
