Where:

WHC = Mass rate of HC in exhaust [g/hr],

GAIRD = Intake air mass flow rate on dry basis [g/hr],

GFUEL = Fuel mass flow rate [g/hr],

MHCexh = Molecular weight of hydrocarbons in the exhaust, see the following equation:

Where:

α = Hydrogen/carbon atomic ratio of the fuel

β = Oxygen/carbon atomic ratio of the fuel

Mexh = Molecular weight of the total exhaust, see the following equation:

Where:

WHC = HC volume concentration in exhaust, ppmC wet

WCO = CO percent concentration in the exhaust, wet

DCO = CO percent concentration in the exhaust, dry

WCO2 = CO2 percent concentration in the exhaust, wet

DCO2 = CO2 percent concentration in the exhaust, dry

WNOX = NO volume concentration in exhaust, ppm wet

WO2 = O2 percent concentration in the exhaust, wet

WH2 = H2 percent concentration in exhaust, wet

K = correction factor to be used when converting dry measurements to a wet basis. Therefore, wet concentration = dry concentration × K,

where K is:

DH2 = H2 percent concentration in exhaust, dry, calculated from the following equation:

Wco = Mass rate of CO in exhaust, [g/hr]

Mco = Molecular weight of CO = 28.01

WNOx = Mass rate of NOX in exhaust, [g/hr]

MNO2 = Molecular weight of NO2 = 46.01

KH = Factor for correcting the effects of humidity on NO2 formation for 4-stroke gasoline small engines, as follows:

KH = (9.953 × H + 0.832)

Where:

H = the amount of water in an ideal gas; 40 CFR 1065.645 describes how to determine this value (referred to as xH2O).

KH = 1 for two-stroke gasoline engines.

Where:

WHC = Mass rate of HC in exhaust, [g/hr]

MHCexh = Molecular weight of hydrocarbons in the exhaust, see following equation:

MC = Molecular weight of carbon = 12.01 [g/mole]

MH = Molecular weight of hydrogen = 1.008 [g/mole]

MO = Molecular weight of oxygen = 16.00 [g/mole]

α = Hydrogen to carbon ratio of the test fuel

β = Oxygen to carbon ratio of the test fuel

MF = Molecular weight of test fuel

GFUEL = Fuel mass flow rate, [g/hr]

TC = Total carbon in exhaust, see following equation:

WCO = CO percent concentration in the exhaust, wet

WCO2 = CO2 percent concentration in the exhaust, wet

DCO = CO percent concentration in the exhaust, dry

DCO2 = CO2 percent concentration in the exhaust, dry

WHC = HC volume concentration in exhaust, ppmC wet

WNOX = NOX volume concentration in exhaust, ppm wet

K = correction factor to be used when converting dry measurements to a wet basis. Therefore, wet concentration = dry concentration × K, where K is:

DH2 = H2 percent concentration in exhaust, dry, calculated from the following equation:

WCO = Mass rate of CO in exhaust, [g/hr]

MCO = Molecular weight of CO = 28.01

WNOX = Mass rate of NOX in exhaust, [g/hr]

MNO2 = Molecular weight of NO2 = 46.01

KH = Factor for correcting the effects of humidity on NO2 formation for 4-stroke gasoline small engines, as follows:

KH = (9.953 × H + 0.832)

Where:

H = the amount of water in an ideal gas; 40 CFR 1065.645 describes how to determine this value (referred to as xH2O).

KH = 1 for two-stroke gasoline engines.

Where:

AWM = Final weighted brake-specific mass emission rate (HC, CO, NOX) [g/kW-hr]

Wi = Mass emission rate during mode i [g/hr]

WFi = Weighting factors for each mode according to §90.410(a)

Pi = Gross average power generated during mode i [kW], calculated from the following equation,

Where:

speed = average engine speed measured during mode i [rev./minute]

torque = average engine torque measured during mode i [N-m]