Home
gpo.gov
govinfo.gov

e-CFR Navigation Aids

Browse

Simple Search

Advanced Search

 — Boolean

 — Proximity

 

Search History

Search Tips

Corrections

Latest Updates

User Info

FAQs

Agency List

Incorporation By Reference

eCFR logo

Related Resources

Electronic Code of Federal Regulations

We invite you to try out our new beta eCFR site at https://ecfr.federalregister.gov. We have made big changes to make the eCFR easier to use. Be sure to leave feedback using the Feedback button on the bottom right of each page!

e-CFR data is current as of November 24, 2020

Title 40Chapter ISubchapter CPart 90Subpart E → §90.426


Title 40: Protection of Environment
PART 90—CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR BELOW 19 KILOWATTS
Subpart E—Gaseous Exhaust Test Procedures


§90.426   Dilute emission sampling calculations—gasoline fueled engines.

(a) The final reported emission test results must be computed by use of the following formula:

eCFR graphic er03jy95.036.gif

View or download PDF

Where:

AWM = Final weighted brake-specific mass emission rate for an emission (HC, CO, CO2, or NOX) [g/kW-hr]

Wi = Average mass flow rate of an emission (HC, CO, CO2, NOX) from a test engine during mode i [g/hr]

WFi = Weighting factor for each mode i as defined in §90.410(a).

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

eCFR graphic er03jy95.037.gif

View or download PDF

Where:

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

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

KHi = NOX humidity correction factor for mode i. This correction factor only affects calculations for tion factor only affects calculations for NOX and is equal to one for all other emissions. KHi is also equal to 1 for all two-stroke engines.

(b) The mass flow rate, Wi in g/hr, of an emission for mode i is determined from the following equation:

eCFR graphic er08oc08.081.gif

View or download PDF

Where:

QI = Volumetric flow rate [m3/HR at stp].

Density = Density of a specific emission (DensityHC, DensityCO, DensityCO2, Density NOX) [g/m3].

DFi = Dilution factor of the dilute exhaust during mode i.

CDi = Concentration of the emission (HC, CO, NOX) in dilute exhaust extracted from the CVS during mode i [ppm].

CBi = Concentration of the emission (HC, CO, NOX) in the background sample during mode i [ppm].

STP = Standard temperature and pressure. All volumetric calculations made for the equations in this section are to be corrected to a standard temperature of 20 °C and a standard pressure of 101.3 kPa.

(c) Densities for emissions that are to be measured for this test procedure are:

DensityHC = 576.8 g/m3

DensityNOX = 1912 g/m3

DensityCO = 1164 g/m3

DensityCO2 = 1829 g/m3

(1) The value of DensityHC above is calculated based on the assumption that the fuel used has a hydrogen to carbon ratio of 1:1.85. For other fuels DensityHC can be calculated from the following formula:

eCFR graphic er08oc08.082.gif

View or download PDF

Where:

MHC = The molecular weight of the hydrocarbon molecule divided by the number of carbon atoms in the molecule [g/mole].

RSTP = Ideal gas constant for a gas at STP = 0.024065 [m3·mole]

(2) The idealized molecular weight of the exhaust hydrocarbons, i.e., the molecular weight of the hydrocarbon molecule divided by the number of carbon atoms in the molecule, MHC, can be calculated from the following formula:

eCFR graphic er03jy95.040.gif

View or download PDF

Where:

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

(3) The value of DensityNOX above assumes that NOX is entirely in the form of NO2

(d) The dilution factor, DF, is the ratio of the volumetric flow rate of the background air to that of the raw engine exhaust. The following formula is used to determine DF:

eCFR graphic er08oc08.083.gif

View or download PDF

Where:

CDHC = Concentration of HC in the dilute sample [ppm].

CDCO = Concentration of CO in the dilute sample [ppm].

CDCO2 = Concentration of CO2 in the dilute sample [ppm].

(e) The humidity correction factor KH is an adjustment made to measured NOX values. This corrects for the sensitivity that a spark-ignition engine has to the humidity of its combustion air. The following formula is used to determine KH for NOX calculations:

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.

(f)-(g) [Reserved]

(h) The fuel mass flow rate, Fi, can be either measured or calculated using the following formula:

eCFR graphic er03jy95.046.gif

View or download PDF

Where:

MFUEL = Mass of fuel consumed by the engine during the mode [g]

T = Duration of the sampling period [hr]

(i) The mass of fuel consumed during the mode smpling period, MFUEL, can be calculated from the following equation:

eCFR graphic er08oc08.084.gif

View or download PDF

Where:

GS = Mass of carbon measured during the mode sampling period [g].

R2 = The fuel carbon weight fraction, which is the mass of carbon in fuel per mass of fuel [g/g].

(j) The grams of carbon measured during the mode, GS, can be calculated from the following equation:

eCFR graphic er08oc08.085.gif

View or download PDF

Where:

HCmass = mass of hydrocarbon emissions for the mode sampling period [grams].

COmass mass of carbon monoxide emissions for the mode sample period [grams].

CO2mass = mass of carbon dioxide emissions for the mode sample period [grams].

α = The atomic hydrogen-to-carbon ratio of the fuel.

[60 FR 34598, July 3, 1995, as amended at 70 FR 40450, July 13, 2005; 73 FR 59182, Oct. 8, 2008]

Need assistance?