90.419 Raw emission sampling calculations - gasoline fueled engines.

§ 90.419 Raw emission sampling calculations - gasoline fueled
engines.

(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:

$$ Where: WHC = Mass rate of HC in exhaust [g/hr],
GAIRD = Intake air mass flow rate on dry basis [g/hr], GFUEL = Fuel
mass flow rate [g/hr], MHCexh = Molecular weight of hydrocarbons in
the exhaust, see the following equation: $$ 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.

(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.

$$ Where: WHC = Mass rate of HC in exhaust, [g/hr]
MHCexh = Molecular weight of hydrocarbons in the exhaust, see
following equation: $$ 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.

(d) Calculate the final weighted brake-specific emission rate
for each individual gas component using the following equation:

$$ Where: AWM = Final weighted brake-specific mass
emission rate (HC, CO, NOX) [g/kW-hr] Wi = Mass emission rate
during mode i [g/hr] WFi = Weighting factors for each mode
according to § 90.410(a) Pi = Gross average power generated during
mode i [kW], calculated from the following equation,
$$ Where: speed = average engine speed measured
during mode i [rev./minute] torque = average engine torque measured
during mode i [N-m] [60 FR 34598, July 13, 1995, as amended at 70
FR 40449, July 13, 2005]