SAE J1349 Dyno Correction Factor

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.

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.

The J1349 correction relation is a published SAE formula; the observed power, barometric pressure, temperature, and humidity come from the dyno cell.

Estimate. AHJ and licensed professional govern.

Field names used by the API: observed_hp, baro_mbar, air_temp_c, cf, corrected_hp

• Dry pressure subtract the water-vapor pressure before applying the factor; humid air makes less powerSAE J1349
• Validity window valid about 15 to 35 C and 900 to 1050 mbar; flagged outsideSAE J1349
• STD vs SAE the STD (J607) basis runs about 4% higher and cannot be compared to a J1349 numberSAE J607