# 40 CFR 91.419 - Raw emission sampling calculations.

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

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

*FUEL*= Fuel mass flow rate [g/hr],

*HCexh*= Molecular weight of hydrocarbons in the exhaust; see the following equation:

*HCexh*= 12.01 1.008 × α

*exh*=Molecular weight of the total exhaust; see the following equation:

*2*= CO

*2*percent concentration in the exhaust, wet

*2*= CO

*2*percent concentration in the exhaust, dry

*X*= NO volume concentration in exhaust, ppm wet

*2*= H

*2*percent concentration in exhaust, wet

*2*= H

*2*percent concentration in exhaust, dry, calculated from the following equation:

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

*CO*= Molecular weight of CO = 28.01

*NOx*= Mass rate of NO

*X*in exhaust, [g/hr]

*NO2*= Molecular weight of NO

*2*= 46.01

*H*= Factor for correcting the effects of humidity on NO

*2*formation for four-stroke gasoline engines; see the equation below:

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

*F*= Molecular weight of test fuel; see following equation:

*FUEL*= Fuel mass flow rate, [g/hr]

*2*= CO

*2*percent concentration in the exhaust, wet

*2*= CO

*2*percent concentration in the exhaust, dry

*X*= NO volume concentration in exhaust, ppm wet

*2*percent concentration in exhaust, wet

*2*= H

*2*percent concentration in exhaust, dry, calculated from the following equation:

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

*CO*= Molecular weight of CO = 28.01

*NOx*= Mass rate of NO

*X*in exhaust, [g/hr]

*NO2*= Molecular weight of NO

*2*= 46.01

*H*= Factor for correcting the effects of humidity on NO

*2*formation for four-stroke gasoline engines; see the equation below:

*wm*= Weighted mass emission level (HC, CO, NO

*X*) for a test [g/kW-hr].

*i*= Average mass flow rate (W

*HC*, W

*CO*, W

*NOx*) of an emission from the test engine during mode i, [g/hr].

*i*= Weighting factors for each mode according to § 91.410(a)

*i*= Average power measured during mode i, [kW], calculated according to the formula given in § 91.423(b). Power for the idle mode shall always be zero for this calculation.

*i*= Fuel mass flow rate of the engine during mode i, [g/hr].

*i*= Weighting factors for each mode according to § 91.410(a)

*i*= Average power measured during mode i, [kW], calculated according to the formula given in § 91.423(b). Power for the idle mode shall always be zero for this calculation.

(a) Derive the final test results through the steps described in this section.

(b) Air and fuel flow method. If both air and fuel flow mass rates are measured, the following equations are used to determine the weighted emission values for the test engine:

For two-stroke gasoline engines, KH should be set to 1.

(c) Fuel flow method. The following equations are to be used when fuel flow is selected as the basis for mass emission calculations using the raw gas method.

For two-stroke gasoline engines, KH should be set to 1.

(d) The final reported emission test results must be computed by using the following formula for each individual gas component:

(e) The final reported weighted brake-specific fuel consumption (WBSFC) shall be computed by use of the following formula: