# 40 CFR 90.419 - Raw emission sampling calculations

(a)
Derive the final weighted brake-specific mass emission rates (g/kW-hr) through the steps described in this section.

(b)

*Air and fuel flow method.*If both air and fuel flow mass rates are measured, use the following equations to determine the weighted emission values for the test engine:Where:

W

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

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

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

*HCexh*= 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

M

*exh*= 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

WCO

*2*= CO*2*percent concentration in the exhaust, wetDCO

*2*= CO*2*percent concentration in the exhaust, dryWNO

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

*2*= O*2*percent concentration in the exhaust, wetWH

*2*= H*2*percent concentration in exhaust, wetK = correction factor to be used when converting dry measurements to a wet basis. Therefore, wet concentration=dry concentration × K,

where K is:

DH

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

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

*co*= Molecular weight of CO=28.01W

*NOx*= Mass rate of NO*X*in exhaust, [g/hr]M

*NO2*= Molecular weight of NO*2*=46.01K

*H*= Factor for correcting the effects of humidity on NO*2*formation for 4-stroke gasoline small engines, as follows:K

*H*= (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 x

*H**2**O*).K

*H*= 1 for two-stroke gasoline engines.
(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.Where:

W

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

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

*C*= Molecular weight of carbon=12.01 [g/mole]M

*H*= Molecular weight of hydrogen=1.008 [g/mole]M

*O*= 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

M

*F*= Molecular weight of test fuelG

*FUEL*= Fuel mass flow rate, [g/hr]TC=Total carbon in exhaust, see following equation:

WCO = CO percent concentration in the exhaust, wet

WCO

*2*= CO*2*percent concentration in the exhaust, wetDCO = CO percent concentration in the exhaust, dry

DCO

*2*= CO*2*percent concentration in the exhaust, dryWHC = HC volume concentration in exhaust, ppmC wet

WNO

*X*= NO*X*volume concentration in exhaust, ppm wetK = correction factor to be used when converting dry measurements to a wet basis. Therefore, wet concentration=dry concentration×K, where K is:

DH

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

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

*CO*= Molecular weight of CO = 28.01WNO

*X*= Mass rate of NO*X*in exhaust, [g/hr]MNO

*2*= Molecular weight of NO*2*=46.01K

*H*= Factor for correcting the effects of humidity on NO*2*formation for 4-stroke gasoline small engines, as follows:K

*H*= (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 x

*H**2**O*).K

*H*= 1 for two-stroke gasoline engines.
(d)
Calculate the final weighted brake-specific emission rate for each individual gas component using the following equation:

Where:

A

*WM*= Final weighted brake-specific mass emission rate (HC, CO, NO*X*) [g/kW-hr]W

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

*i*= Weighting factors for each mode according to § 90.410(a)P

*i*= 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]

[60 FR 34598, July 13, 1995, as amended at 70 FR 40449, July 13, 2005]

**Title 40 published on 2013-07-01**

no entries appear in the Federal Register **after** this date.