The procedures in this part generally follow either the International System of Units (SI) or the United States customary units, as detailed in NIST Special Publication 811, which we incorporate by reference in Sec. 1066.1010. See 40 CFR 1065.20 for specific provisions related to these conventions. This section summarizes the way we use symbols, units of measure, and other abbreviations.
(a) Symbols for quantities. This part uses the following symbols and units of measure for various quantities: ----------------------------------------------------------------------------------------------------------------
Unit in terms of
Symbol Quantity Unit Unit symbol SI base units----------------------------------------------------------------------------------------------------------------a............................... atomic hydrogen to mole per mole..... mol/mol........... 1
carbon ratio.A............................... area.............. square meter...... m\2\.............. m\2\A............................... vehicle frictional pound force or lbf or N.......... kg [middot] s-2
load. newton.
Am.............................. calculated vehicle pound force or lbf or N.......... kg [middot] s-2
frictional load. newton.a0.............................. intercept of least
squares
regression.a1.............................. slope of least
squares
regression.a............................... acceleration...... feet per second ft/s\2\ or m/s\2\. m [middot] s-2
squared or meters
per second
squared.B............................... vehicle load from pound force per lbf/mph or N kg [middot] s-1
drag and rolling mile per hour or [middot] s/m. [middot] m-1
resistance. newton second per
meter.b............................... ratio of diameters meter per meter... m/m............... 1b............................... atomic oxygen to mole per mole..... mol/mol........... 1
carbon ratio.c............................... conversion factor.C............................... vehicle-specific pound force per lbf/mph\2\ or N kg [middot] m-2
aerodynamic mile per hour [middot] s\2\/
effects. squared or newton m\2\.
second squared
per meter squared.C.............................. number of carbon C................ number of carbon C
atoms in a atoms in a
molecule. molecule.Cd.............................. discharge
coefficient.CDA............................. drag area......... meter squared..... m\2\.............. m\2\Cf.............................. flow coefficient..Cp.............................. heat capacity at joule per kelvin.. J/K............... J [middot] K-1
constant pressure.Cv.............................. heat capacity at joule per kelvin.. J/K............... J [middot] K-1
constant volume.d............................... diameter.......... meters............ m................. mD............................... distance.......... miles or meters... mi or m........... mD............................... slope correlation. pound force per lbf/mph\2\ or N kg [middot] m-2
mile per hour [middot] s\2\/
squared or newton m\2\.
second squared
per meter squared.DF.............................. dilution factor... .................. .................. 1e............................... mass weighted grams/mile........ g/mi..............
emission result.F............................... force............. pound force or lbf or N.......... kg [middot] s-2
newton.f............................... frequency......... hertz............. Hz................ s-1fn.............................. angular speed revolutions per r/min............. 2 [middot] [pi]
(shaft). minute. [middot] 60-1
[middot] m
[middot] m-1
[middot] s-1FC.............................. friction horsepower or watt W................. kg [middot] m\2\
compensation [middot] s-3
error.FR.............................. Road-load force... pound force or lbf or N.......... kg [middot] s-2
newton.g............................... gravitational meters per second m/s\2\............ m [middot] s-2
acceleration. squared.g............................... ratio of specific (joule per (J/(kg [middot] 1
heats. kilogram kelvin) K))/(J/(kg
per (joule per [middot] K)).
kilogram kelvin).H............................... ambient humidity.. grams water vapor g H2O vapor/kg dry g H2O vapor/kg dry
per kilogram dry air. air
air.[Delta]h........................ change in height.. meters............ m................. mI............................... inertia........... pound mass or lbm or kg......... kg
kilogram.I............................... current........... ampere............ A................. Ai............................... indexing variable.IR.............................. inertia work
rating.K............................... correction factor. .................. .................. 1Kv.............................. calibration .................. m\4\ [middot] s m\4\ [middot] s
coefficient. [middot] K\0.5\/ [middot] K\0.5\
kg. [middot] kg-1m............................... viscosity, dynamic pascal second..... Pa [middot] s..... m-1 [middot] kg
[middot] s-1M............................... molar mass........ gram per mole..... g/mol............. 10-3 [middot] kg
[middot] mol-1Me.............................. effective mass.... kilogram.......... kg................ kgm............................... mass.............. pound mass or lbm or kg......... kg
kilogram.N............................... total number in
series.n............................... total number of
pulses in a
series.p............................... pressure.......... pascal............ Pa................ m-1 [middot] kg
[middot] s-2[Delta]p........................ differential pascal............ Pa................ m-1 [middot] kg
static pressure. [middot] s-2pd.............................. saturated vapor kilopascal........ kPa............... m-1 [middot] kg
pressure at [middot] s-2
ambient dry bulb
temperature.PF.............................. penetration
fraction.Q............................... flow.............. cubic feet or ft\3\ or m\3\..... m\3\
cubic meter.Q............................... flow rate......... cubic feet per ft\3\/min or m\3\/ m\3\/s
minute or cubic s.
meter per second.r............................... mass density...... kilogram per cubic kg/m\3\........... kg [middot] m-3
meter.R............................... dynamometer roll revolutions per rpm............... 2 [middot] [pi]
revolutions. minute. [middot] 60-1
[middot] m
[middot] m-1
[middot] s-1r............................... ratio of pressures pascal per pascal. Pa/Pa............. 1r \2\........................... coefficient of
determination.Re............................. Reynolds number...
RF.............................. response factor...RH.............................. relative humidity.S............................... Sutherland kelvin............ K................. K
constant.SEE............................. standard estimate
of error.SG.............................. specific gravity..[Delta]s........................ distance traveled meters............ m................. m
during
measurement
interval.T............................... absolute kelvin............ K................. K
temperature.T............................... Celsius degree Celsius.... [deg]C............ K - 273.15
temperature.T............................... torque (moment of newton meter...... N [middot] m...... m\2\ [middot] kg
force). [middot] s-2t............................... time.............. second............ s................. s[Delta]t........................ time interval, second............ s................. s
period, 1/
frequency.U............................... voltage........... volt.............. V................. m\2\ [middot] kg
[middot] s-3
[middot] A-1v............................... speed............. miles per hour or mph or m/s........ m [middot] s-1
meters per second.V............................... volume............ cubic meter....... m\3\.............. m\3\VP.............................. volume percent....x............................... concentration of part per million.. ppm...............
emission over a
test interval.y............................... generic variable..Z............................... compressibility Z................. compressibility Z
factor. factor.----------------------------------------------------------------------------------------------------------------
(b) Symbols for chemical species. This part uses the following symbols for chemical species and exhaust constituents: ------------------------------------------------------------------------
Symbol Species------------------------------------------------------------------------CH4............................... methane.CH3OH............................. methanol.CH2O.............................. formaldehyde.C2H4O............................. acetaldehyde.C2H5OH............................ ethanol.C2H6.............................. ethane.C3H7OH............................ propanol.C3H8.............................. propane.C4H10............................. butane.C5H12............................. pentane.CO................................ carbon monoxide.CO2............................... carbon dioxide.H2O............................... water.HC................................ hydrocarbon.N2................................ molecular nitrogen.NMHC.............................. nonmethane hydrocarbon.NMHCE............................. nonmethane hydrocarbon equivalent.NMOG.............................. nonmethane organic gas.NO................................ nitric oxide.NO2............................... nitrogen dioxide.NOX............................... oxides of nitrogen.N2O............................... nitrous oxide.O2................................ molecular oxygen.OHC............................... oxygenated hydrocarbon.PM................................ particulate matter.THC............................... total hydrocarbon.THCE.............................. total hydrocarbon equivalent.------------------------------------------------------------------------
(c) Superscripts. This part uses the following superscripts to define a quantity: ------------------------------------------------------------------------
Superscript Quantity------------------------------------------------------------------------overbar (such as y)....................... arithmetic mean.overdot (such as y)....................... quantity per unit time.------------------------------------------------------------------------
(d) Subscripts. This part uses the following subscripts to define a quantity: ------------------------------------------------------------------------
Subscript Quantity------------------------------------------------------------------------0................................. reference.abs............................... absolute quantity.AC17.............................. air conditioning 2017 test interval.act............................... actual or measured condition.actint............................ actual or measured condition over
the speed interval.adj............................... adjusted.air............................... air, dry.atmos............................. atmospheric.b................................. base.bkgnd............................. background.c................................. cold.comp.............................. composite.cor............................... corrected.cs................................ cold stabilized.ct................................ cold transient.cUDDS............................. cold-start UDDS.D................................. driven.dew............................... dewpoint.dexh.............................. dilute exhaust quantity.dil............................... dilute.e................................. effective.emission.......................... emission specie.error............................. error.EtOH.............................. ethanol.exh............................... raw exhaust quantity.exp............................... expected quantity.fil............................... filter.final............................. final.flow.............................. flow measurement device type.gas............................... gaseous.h................................. hot.HFET.............................. highway fuel economy test.hs................................ hot stabilized.ht................................ hot transient.hUDDS............................. hot-start UDDS.i................................. an individual of a series.ID................................ driven inertia.in................................ inlet.int............................... intake.init.............................. initial quantity, typically before
an emission test.IT................................ target inertia.
liq............................... liquid.max............................... the maximum (i.e. peak) value
expected at the standard over a
test interval; not the maximum of
an instrument range.meas.............................. measured quantity.mix............................... dilute exhaust gas mixture.out............................... outlet.PM................................ particulate matter.record............................ record.ref............................... reference quantity.rev............................... revolution.roll.............................. dynamometer roll.s................................. settling.s................................. slip.s................................. stabilized.sat............................... saturated condition.SC03.............................. air conditioning driving schedule.span.............................. span quantity.sda............................... secondary dilution air.std............................... standard conditions.T................................. target.t................................. throat.test.............................. test quantity.uncor............................. uncorrected quantity.w................................. weighted.zero.............................. zero quantity.------------------------------------------------------------------------
(e) Other acronyms and abbreviations. This part uses the following additional abbreviations and acronyms: ------------------------------------------------------------------------
------------------------------------------------------------------------A/C............................... air conditioning.AC17.............................. air conditioning 2017 test interval.ALVW.............................. adjusted loaded vehicle weight.ASME.............................. American Society of Mechanical
Engineers.CFR............................... Code of Federal Regulations.CFV............................... critical-flow venturi.CNG............................... compressed natural gas.CVS............................... constant-volume sampler.EPA............................... Environmental Protection Agency.ETW............................... equivalent test weight.EV................................ electric vehicle.FID............................... flame-ionization detector.FTP............................... Federal test procedure.GC................................ gas chromatograph.GEM............................... greenhouse gas emissions model.GHG............................... greenhouse gas (including CO2, N2O,
and CH4).GPS............................... global positioning system.GVWR.............................. gross vehicle weight rating.HEV............................... hybrid electric vehicle, including
plug-in hybrid electric vehicles.HFET.............................. highway fuel economy test.HLDT.............................. heavy light-duty truck.HPLC.............................. high pressure liquid chromatography.IBR............................... incorporated by reference.LA-92............................. Los Angeles 1992 driving schedule.MDPV.............................. medium-duty passenger vehicle.NIST.............................. National Institute for Standards and
Technology.NMC............................... nonmethane cutter.PDP............................... positive-displacement pump.PHEV.............................. plug-in hybrid electric vehicle.PM................................ particulate matter.RESS.............................. rechargeable energy storage system.ppm............................... parts per million.SAE............................... Society of Automotive Engineers.SC03.............................. air conditioning driving schedule.SEA............................... selective enforcement audit.SFTP.............................. supplemental federal test procedure.SI................................ International System of Units.SSV............................... subsonic venturi.UDDS.............................. urban dynamometer driving schedule.US06.............................. aggressive driving schedule.U.S.C............................. United States Code.WWV............................... NIST radio station call sign.------------------------------------------------------------------------
(f) This part uses the following densities of chemical species: ----------------------------------------------------------------------------------------------------------------
Symbol Quantity 1 2 g/m\3\ g/ft\3\----------------------------------------------------------------------------------------------------------------rCH4................................ density of methane.................... 666.905 18.8847rCH3OH.............................. density of methanol................... 1332.02 37.7185rC2H5OH............................. C1-equivalent density of ethanol...... 957.559 27.1151rC2H4O.............................. C1-equivalent density of acetaldehyde. 915.658 25.9285rC3H8............................... density of propane.................... 611.035 17.3026rC3H7OH............................. C1-equivalent density of propanol..... 832.74 23.5806rCO................................. density of carbon monoxide............ 1164.41 32.9725rCO2................................ density of carbon dioxide............. 1829.53 51.8064rHC-gas............................. effective density of hydrocarbon-- (see 3) (see 3)
gaseous fuel \3\.rCH2O............................... density of formaldehyde............... 1248.21 35.3455rHC-liq............................. effective density of hydrocarbon-- 576.816 16.3336
liquid fuel \4\.rNMHC-gas........................... effective density of nonmethane (see 3) (see 3)
hydrocarbon--gaseous fuel \3\.rNMHC-liq........................... effective density of nonmethane 576.816 16.3336
hydrocarbon--liquid fuel \4\.rNMHCE-gas.......................... effective density of nonmethane (see 3) (see 3)
equivalent hydrocarbon--gaseous fuel
\3\.rNMHCE-liq.......................... effective density of nonmethane 576.816 16.3336
equivalent hydrocarbon--liquid fuel
\4\.rNOx................................ effective density of oxides of 1912.5 54.156
nitrogen \5\.rN2O................................ density of nitrous oxide.............. 1829.66 51.8103rTHC-liq............................ effective density of total 576.816 16.3336
hydrocarbon--liquid fuel \4\.rTHCE-liq........................... effective density of total equivalent 576.816 16.3336
hydrocarbon--liquid fuel \4\.----------------------------------------------------------------------------------------------------------------\1\ Densities are given at 20 [deg]C and 101.325 kPa.\2\ Densities for all hydrocarbon containing quantities are given in g/m\3\-carbon atom and g/ft\3\-carbon atom.\3\ The effective density for natural gas fuel and liquefied petroleum gas fuel are defined by an atomic
hydrogen-to-carbon ratio, a, of the hydrocarbon components of the test fuel. rHCgas = 41.57 [middot] (12.011 +
(a [middot] 1.008)).\4\ The effective density for gasoline and diesel fuel are defined by an atomic hydrogen-to-carbon ratio, a, of
1.85.\5\ The effective density of NOX is defined by the molar mass of nitrogen dioxide, NO2.
(g) Constants. (1) This part uses the following constants for the composition of dry air: ------------------------------------------------------------------------
Symbol Quantity mol/mol------------------------------------------------------------------------xArair.................. amount of argon in dry air 0.00934xCO2air................. amount of carbon dioxide 0.000375
in dry air.xN2air.................. amount of nitrogen in dry 0.78084
air.xO2air.................. amount of oxygen in dry 0.209445
air.------------------------------------------------------------------------
(2) This part uses the following molar masses or effective molar masses of chemical species: ------------------------------------------------------------------------
g/mol (10-3
Symbol Quantity [middot] kg
[middot] mol-1)------------------------------------------------------------------------Mair.................... molar mass of dry air \1\. 28.96559MH2O.................... molar mass of water....... 18.01528------------------------------------------------------------------------\1\ See paragraph (g)(1) of this section for the composition of dry air.
(3) This part uses the following molar gas constant for ideal gases: ------------------------------------------------------------------------
J/(mol [middot] K)
(m\2\ [middot] kg
Symbol Quantity [middot] s-2
[middot] mol-1
[middot] K-1)------------------------------------------------------------------------R....................... molar gas constant........ 8.314472------------------------------------------------------------------------
(h) Prefixes. This part uses the following prefixes to define a quantity: ------------------------------------------------------------------------
Symbol Quantity Value------------------------------------------------------------------------n................................. nano................ 10-\9\[micro]........................... micro............... 10-\6\m................................. milli............... 10-\3\c................................. centi............... 10-\2\k................................. kilo................ 10\3\M................................. mega................ 10\6\------------------------------------------------------------------------ [79 FR 23823, Apr. 28, 2014, as amended at 80 FR 9124, Feb. 19, 2015]