This is the real reason why manufacturers claimed Hp don't match real dyno tests...the most reliable source for real Hp comes from Nytrodyne Systems tests, because all engines are tested in equal enviroment conditions and using SAE correction factors, which gives us a real comparison table.

AFM

X-Dyno Horsepower vs. Claimed Horsepower

You may have noticed that X-Dyno power data doesn’t always match up with manufacturers’ claimed horsepower and torque figures. We attribute this discrepancy to the fact that many manufacturers publish theoretical horsepower and torque figures based on rough estimates rather than actual dyno data, or that a manufacturer’s data collection protocol doesn’t match our own. The X-Dyno calculates horsepower using known mathematical formulas and precise physical data measurement.Although the X-Dyno’s power numbers may not equal the numbers you’re accustomed to seeing, the figures we provide are accurate from engine to engine, and are directly comparable with power data from test to test.