(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: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] 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:MHCexh = 12.01 + 1.008 x [alpha]Where: [alpha]=Hydrocarbon/carbon atomic ratio of the fuel.Mexh=Molecular weight of the total exhaust; see the following
equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: WHC = HC volume concentration in exhaust, ppmC wetWCO = CO percent concentration in the exhaust, wetDCO = CO percent concentration in the exhaust, dryWCO2 = CO2 percent concentration in the exhaust,
wet DCO2 = CO2 percent concentration in the exhaust,
dryWNOX = NO volume concentration in exhaust, ppm wetWH2 = H2 percent concentration in exhaust, wetK = correction factor to be used when converting dry measurements to a
wet basis. Therefore, wet concentration = dry concentration x
K, where K is:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
DH2 = H2 percent concentration in exhaust, dry,
calculated from the following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
WCO = Mass rate of CO in exhaust, [g/hr]MCO = Molecular weight of CO = 28.01WNOx = Mass rate of NOX in exhaust, [g/hr]MNO2 = Molecular weight of NO2 = 46.01KH = Factor for correcting the effects of humidity on
NO2 formation for four-stroke gasoline engines; see
the equation below:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: H = specific humidity of the intake air in grams of moisture per
kilogram of dry air.
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. [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where: WHC = Mass rate of HC in exhaust, [g/hr]MF = Molecular weight of test fuel; see following equation: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] GFUEL = Fuel mass flow rate, [g/hr]TC = Total carbon; see following equation: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] WHC = HC volume concentration in exhaust, ppmC wetWCO = CO percent concentration in the exhaust, wetDCO = CO percent concentration in the exhaust, dryWCO2 = CO2 percent concentration in the exhaust,
wetDCO2 = CO2 percent concentration in the exhaust,
dryWNOX = NO volume concentration in exhaust, ppm wetWH2 = H2 percent concentration in exhaust, wetK = correction factor to be used when converting dry measurements to a
wet basis. Therefore, wet concentration = dry concentration x
K, where K is: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] DH2 = H2 percent concentration in exhaust, dry,
calculated from the following equation:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
WCO = Mass rate of CO in exhaust, [g/hr]MCO = Molecular weight of CO = 28.01WNOx = Mass rate of NOX in exhaust, [g/hr]MNO2 = Molecular weight of NO2 = 46.01KH = Factor for correcting the effects of humidity on
NO2 formation for four-stroke gasoline engines; see
the equation below:
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Where: H = specific humidity of the intake air in grams of moisture per
kilogram of dry air.
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: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where: Ywm = Weighted mass emission level (HC, CO, NOX)
for a test [g/kW-hr].Wi = Average mass flow rate (WHC, WCO,
WNOx) of an emission from the test engine during
mode i, [g/hr].fi = Weighting factors for each mode according to
Sec. 91.410(a)Pi = Average power measured during mode i, [kW], calculated
according to the formula given in Sec. 91.423(b). Power for
the idle mode shall always be zero for this calculation.
(e) The final reported weighted brake-specific fuel consumption (WBSFC) shall be computed by use of the following formula: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where: WBSFC = Weighted brake-specific fuel consumption in grams of fuel per
kilowatt-hour (g/kW-hr).Fi = Fuel mass flow rate of the engine during mode i, [g/hr].fi = Weighting factors for each mode according to
Sec. 91.410(a)Pi = Average power measured during mode i, [kW], calculated
according to the formula given in Sec. 91.423(b). Power for
the idle mode shall always be zero for this calculation. [61 FR 52102, Oct. 4, 1996, as amended at 67 FR 68340, Nov. 8, 2002; 70 FR 40452, July 13, 2005]