CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER U—AIR POLLUTION CONTROLS (Parts 1027–1074) > PART 1065—ENGINE-TESTING PROCEDURES > SUBPART K—Definitions and Other Reference Information (§1065.1001 to §1065.1010) > 1065.1005—Symbols, abbreviations, acronyms, and units of measure.

1065.1005—Symbols, abbreviations, acronyms, and units of measure.

The procedures in this part generally follow the International System of Units (SI), as detailed in NIST Special Publication 811, 1995 Edition, “Guide for the Use of the International System, of Units (SI),” which we incorporate by reference in § 1065.1010. See § 1065.25 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:
Symbol Quantity Unit Unit symbol Base SI units
% percent 0.01 % 10−2
α atomic hydrogen to carbon ratio mole per mole mol/mol 1
A area square meter m2 m2
A 0 intercept of least squares regression
A 1 slope of least squares regression
β ratio of diameters meter per meter m/m 1
β atomic oxygen to carbon ratio mole per mole mol/mol 1
C # number of carbon atoms in a molecule
d Diameter meter m m
DR dilution ratio mole per mol mol/mol 1
ε error between a quantity and its reference
e brake-specific basis gram per kilowatt hour g/(kW.h) g.3.6−1.106.m−2.kgs2
F F-test statistic
f frequency hertz Hz s−1
f n rotational frequency (shaft) revolutions per minute rev/min 2.pi.60−1.s−1
γ ratio of specific heats (joule per kilogram kelvin) per (joule per kilogram kelvin) (J/(kg.K))/(J/(kg.K)) 1
K correction factor 1
l length meter m m
µ viscosity, dynamic pascal second Pa's m−1.kg.s−1
M molar mass1 gram per mole g/mol 10−3.kg.mol−1
m mass kilogram kg kg
m mass rate kilogram per second kg/s kg.s−1
v viscosity, kinematic meter squared per second m2/s m2 .s−1
N total number in series
n amount of substance mole mol mol
n amount of substance rate mole per second mol/s mol.s−1
P power kilowatt kW 103.m2.kg.s−3
PF penetration fraction
p pressure pascal Pa m−1.kg.s−2
ρ mass density kilogram per cubic meter kg/m3 kg.m−3
r ratio of pressures pascal per pascal Pa/Pa 1
R 2 coefficient of determination
Ra average surface roughness micrometer µm m−6
Re # Reynolds number
RF response factor
RH % relative humidity 0.01 % 10−2
σ non-biased standard deviation
S Sutherland constant kelvin K K
SEE standard estimate of error
T absolute temperature kelvin K K
T Celsius temperature degree Celsius °C K-273.15
T torque (moment of force) newton meter N.m m2 .kg.s−2
t time second s s
Δ t time interval, period, 1/frequency second s s
V volume cubic meter m3 m3
V volume rate cubic meter per second m3/s m3 .s−1
W work kilowatt hour kW.h 3.6.10−6.m2 .kg.s−2
w c carbon mass fraction gram per gram g/g 1
x amount of substance mole fraction 2 mole per mole mol/mol 1
X flow-weighted mean concentration mole per mole mol/mol 1
y generic variable
1 See paragraph (f)(2) of this section for the values to use for molar masses. Note that in the cases of NOX and HC, the regulations specify effective molar masses based on assumed speciation rather than actual speciation.
Code of Federal Regulations 753
2 Note that mole fractions for THC, THCE, NMHC, NMHCE, and NOTHC are expressed on a C1 equivalent basis.
(b) Symbols for chemical species. This part uses the following symbols for chemical species and exhaust constituents:
Symbol Species
Ar argon.
C carbon.
CH4 methane.
C2H6 ethane.
C3H8 propane.
C4H10 butane.
C5H12 pentane.
CO carbon monoxide.
CO2 carbon dioxide.
H atomic hydrogen.
H2 molecular hydrogen.
H2O water.
He helium.
85Kr krypton 85.
N2 molecular nitrogen.
NMHC nonmethane hydrocarbon.
NMHCE nonmethane hydrocarbon equivalent.
NO nitric oxide.
NO2 nitrogen dioxide.
NOX oxides of nitrogen.
N2O nitrous oxide.
NOTHC nonoxygenated hydrocarbon.
O2 molecular oxygen.
OHC oxygenated hydrocarbon.
210Po polonium 210.
PM particulate mass.
S sulfur.
SO2 sulfur dioxide.
THC total hydrocarbon.
ZrO2 zirconium dioxide.
(c) Prefixes. This part uses the following prefixes to define a quantity:
Symbol Quantity Value
µ micro 10− 6
m milli 10− 3
c centi 10− 2
k kilo 103
M mega 106
(d) 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.
(e) Subscripts. This part uses the following subscripts to define a quantity:
Subscript Quantity
abs absolute quantity.
act actual condition.
air air, dry
atmos atmospheric.
cal calibration quantity.
CFV critical flow venturi.
cor corrected quantity.
dil dilution air.
dexh diluted exhaust.
exh raw exhaust.
exp expected quantity.
i an individual of a series.
idle condition at idle.
in quantity in.
init initial quantity, typically before an emission test.
j an individual of a series.
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.
out quantity out.
part partial quantity.
PDP positive-displacement pump.
ref reference quantity.
rev revolution.
sat saturated condition.
slip PDP slip.
span span quantity.
SSV subsonic venturi.
std standard condition.
test test quantity.
uncor uncorrected quantity.
zero zero quantity.
(f) Constants. (1) This part uses the following constants for the composition of dry air:
Symbol Quantity mol/mol
x Arair amount of argon in dry air 0.00934
x CO2air amount of carbon dioxide in dry air 0.000375
x N2air amount of nitrogen in dry air 0.78084
x O2air amount of oxygen in dry air 0.209445
(2) This part uses the following molar masses or effective molar masses of chemical species:
Symbol Quantity g/mol(10−3.kg.mol− 1)
M air molar mass of dry air 28.96559
M Ar molar mass of argon 39.948
M C molar mass of carbon 12.0107
M CO molar mass of carbon monoxide 28.0101
M CO2 molar mass of carbon dioxide 44.0095
M H molar mass of atomic hydrogen 1.00794
M H2 molar mass of molecular hydrogen 2.01588
M H2O molar mass of water 18.01528
M He molar mass of helium 4.002602
M N molar mass of atomic nitrogen 14.0067
Code of Federal Regulations 754
M N2 molar mass of molecular nitrogen 28.0134
M NMHC effective molar mass of nonmethane hydrocarbon 2 13.875389
M NMHCE effective molar mass of nonmethane equivalent hydrocarbon 2 13.875389
M NOx effective molar mass of oxides of nitrogen 3 46.0055
M N2O effective molar mass of nitrous oxide 44.0128
M O molar mass of atomic oxygen 15.9994
M O2 molar mass of molecular oxygen 31.9988
M C3H8 molar mass of propane 44.09562
M S molar mass of sulfur 32.065
M THC effective molar mass of total hydrocarbon 2 13.875389
M THCE effective molar mass of total hydrocarbon equivalent 2 13.875389
1 See paragraph (f)(1) of this section for the composition of dry air
2 The effective molar masses of THC, THCE, NMHC, and NMHCE are defined by an atomic hydrogen-to-carbon ratio, α, of 1.85
3 The effective molar mass of NOx is defined by the molar mass of nitrogen dioxide, NO2
(3) This part uses the following molar gas constant for ideal gases:
Symbol Quantity J/(mol) · K)(m2·kg·s−2 mol−1· K−1)
R molar gas constant 8.314472
(4) This part uses the following ratios of specific heats for dilution air and diluted exhaust:
Symbol Quantity [J/(kg·K)]/[J/(kg·K)]
γ air ratio of specific heats for intake air or dilution air 1.399
γ dil ratio of specific heats for diluted exhaust 1.399
γ exh ratio of specific heats for raw exhaust 1.385
(g) Other acronyms and abbreviations. This part uses the following additional abbreviations and acronyms:
ASTMAmerican Society for Testing and Materials.
BMDbag mini-diluter.
BSFCbrake-specific fuel consumption.
CARBCalifornia Air Resources Board.
CFRCode of Federal Regulations.
CFVcritical-flow venturi.
CIcompression-ignition.
CITTCurb Idle Transmission Torque.
CLDchemiluminescent detector.
CVSconstant-volume sampler.
DFdeterioration factor.
ECMelectronic control module.
EFCelectronic flow control.
EGRexhaust gas recirculation.
EPAEnvironmental Protection Agency.
FELFamily Emission Limit
FIDflame-ionization detector.
GCgas chromatograph.
GC-ECDgas chromatograph with an electron-capture detector.
IBPinitial boiling point.
ISOInternational Organization for Standardization.
LPGliquefied petroleum gas.
NDIRnondispersive infrared.
NDUVnondispersive ultraviolet.
NISTNational Institute for Standards and Technology.
PDPpositive-displacement pump.
PEMSportable emission measurement system.
PFDpartial-flow dilution.
PMPPolymethylpentene.
pt.a single point at the mean value expected at the standard.

Code of Federal Regulations

PTFEpolytetrafluoroethylene (commonly known as TeflonTM).
RErounding error.
RMCramped-modal cycle.
RMSroot-mean square.
RTDresistive temperature detector.
SSVsubsonic venturi.
SIspark-ignition.
UCLupper confidence limit.
UFMultrasonic flow meter.
U.S.C.United States Code.

Code of Federal Regulations

[70 FR 40516, July 13, 2005, as amended at 73 FR 37346, June 30, 2008; 73 FR 59342, Oct. 8, 2008; 74 FR 56518, Oct. 30, 2009]