SAE J1349 Dyno Correction Factor
The dry-pressure correction that makes two dyno pulls comparable: SAE J1349 corrects observed power to a standard day (25 C, 99 kPa DRY). The catch is 'dry' -- subtract the water-vapor pressure from the barometric before applying, because humid air makes less power. P_dry = baro - vapor; CF = 1.18 x (990/P_dry) x sqrt((T+273)/298) - 0.18; corrected = observed x CF. 400 hp at 980 mbar dry, 30 C -> CF 1.0220 -> 408.8 hp; a hotter, thinner 970 mbar / 35 C day corrects harder, CF 1.0444. Valid only ~15-35 C, 900-1050 mbar (flagged outside); the older STD (J607) basis runs ~4% higher and cannot be compared to SAE. A comparison aid; the dyno and correction basis govern.
Formula and source
vapor = es(temp) x RH/100; P_dry = baro - vapor; CF = 1.18 x (990 / P_dry_mbar) x sqrt((temp_C + 273)/298) - 0.18; corrected = observed x CF.
The SAE J1349 engine power correction factor (STD per SAE J607), correcting observed power to a standard dry day, by name; the dyno, correction basis, and test procedure govern.
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