§ 1065.1005 - Symbols, abbreviations, acronyms, and units of measure.

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

Cross Reference

Link to an amendment published at 88 FR 4689, Jan. 24, 2023.

The procedures in this part generally follow the International System of Units (SI), as detailed in NIST Special Publication 811, which we incorporate by reference in § 1065.1010. See § 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:

Table 1 of § 1065.1005 - Symbols —Symbols for Quantities

Symbol	Quantity	Unit	Unit symbol	Units in terms of SI base units
α	atomic hydrogen-to-carbon ratio	mole per mole	mol/mol	1.
A	area	square meter	m2	m2.
a0	intercept of least squares regression
a1	slope of least squares regression
ag	acceleration of Earth's gravity	meter per square second	m/s2	m· s−2.
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
c	power-specific carbon mass error coefficient	gram per kilowatt-hour	g/(kW·hr)	3.6−1 · 10−9 · m−2 · s2.
Cd	discharge coefficient
Cf	flow coefficient
δ	atomic nitrogen-to-carbon ratio	mole per mole	mol/mol	1.
d	diameter	meter	m	m.
d	power-specific carbon mass rate absolute error coefficent	gram per kilowatt-hour	g/(kW·hr)	3.6−1 · 10−9 · m−2 · s2.
DR	dilution ratio	mole per mole	mol/mol	1.
ε	error between a quantity and its reference
∈	difference or error quantity
e	brake-specific emission or fuel consumption	gram per kilowatt hour	g/(kW·hr)	3.6−1 · 10−9 · m−2 · s2.
F	F-test statistic
ƒ	frequency	hertz	Hz	s−1.
ƒn	angular speed (shaft)	revolutions per minute	r/min	π · 30−1 · s−1.
γ	ratio of specific heats	(joule per kilogram kelvin) per (joule per kilogram kelvin)	(J/(kg·K))/(J/(kg·K))	1.
γ	atomic sulfur-to-carbon ratio	mole per mole	mol/mol	1.
κ	opacity
K	correction factor			1.
Kv	calibration coefficient		m4 · s · K0.5/kg	m4 · kg−1 · s · K0.5.
l	length	meter	m	m.
L	limit
µ	viscosity, dynamic	pascal second	Pa·s	m−1 · kg · s−1.
M	molar mass 1	gram per mole	g/mol	10−3 · kg · mol−1.
m	mass	kilogram	kg	kg.
ṁ	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.
ṅ	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	m−3 · kg.
Δ p	differential static pressure	pascal	Pa	m−1 · kg · s−2.
r	ratio of pressures	pascal per pascal	Pa/Pa	1.
r 2	coefficient of determination
Ra	average surface roughness	micrometer	µm	10−6 · m.
Re#	Reynolds number
RF	response factor
RH	relative humidity
σ	non-biased standard deviation
S	Sutherland constant	kelvin	K	K.
SEE	standard error of the estimate
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.
θ	plane angle	degrees	°	rad.
t	time	second	s	s.
Δ t	time interval, period, 1/frequency	second	s	s.
V	volume	cubic meter	m3	m3.
V̇	volume rate	cubic meter per second	m3/s	m3 · s−1.
W	work	kilowatt-hour	kW·hr	3.6 · 106 · m2 · kg · s−2.
wC	carbon mass fraction	gram per gram	g/g	1.
x	amount of substance mole fraction.2	mole per mole	mol/mol	1.
X̄	flow-weighted mean concentration	mole per mole	mol/mol	1.
y	generic variable
Z	compressibility factor

¹ See paragraph (f)(2) of this section for the values to use for molar masses. Note that in the cases of NO_X and HC, the regulations specify effective molar masses based on assumed speciation rather than actual speciation.

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:

Table 2 of § 1065.1005—Symbols for Chemical Species and Exhaust Constituents

Symbol	Species
Ar	argon.
C	carbon.
CH2O	formaldehyde.
CH2O2	formic acid.
CH3OH	methanol.
CH4	methane.
C2H4O	acetaldehyde.
C2H5OH	ethanol.
C2H6	ethane.
C3H7OH	propanol.
C3H8	propane.
C4H10	butane.
C5H12	pentane.
CO	carbon monoxide.
CO2	carbon dioxide.
H	atomic hydrogen.
H2	molecular hydrogen.
H2O	water.
H2SO4	sulfuric acid.
HC	hydrocarbon.
He	helium.
85Kr	krypton 85.
N2	molecular nitrogen.
NH3	ammonia.
NMHC	nonmethane hydrocarbon.
NMHCE	nonmethane hydrocarbon equivalent.
NMNEHC	nonmethane-nonethane hydrocarbon.
NO	nitric oxide.
NO2	nitrogen dioxide.
NOX	oxides of nitrogen.
N2O	nitrous oxide.
NMOG	nonmethane organic gases.
NONMHC	non-oxygenated nonmethane hydrocarbon.
NOTHC	non-oxygenated total hydrocarbon.
O2	molecular oxygen.
OHC	oxygenated hydrocarbon.
210Po	polonium 210.
PM	particulate matter.
S	sulfur.
SVOC	semi-volatile organic compound.
THC	total hydrocarbon.
THCE	total hydrocarbon equivalent.
ZrO2	zirconium dioxide.

(c) Prefixes. This part uses the following prefixes for units and unit symbols:

Table 3 of § 1065.1005 - Prefixes —Prefixes

Symbol	Prefix name	Factor
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 for modifying quantity symbols:

Table 4 of § 1065.1005 - Superscripts —Superscripts

Superscript	Meaning
overbar (such as ȳ)	arithmetic mean.
overdot (such as ẏ)	quantity per unit time.

(e) Subscripts . This part uses the following subscripts for modifying quantity symbols:

Table 5 of § 1065.1005 - Subscripts —Subscripts

Subscript	Meaning
a	absolute (e.g., absolute difference or error).
abs	absolute quantity.
act	actual condition.
air	air, dry.
amb	ambient.
atmos	atmospheric.
bkgnd	background.
C	carbon mass.
cal	calibration quantity.
CFV	critical flow venturi.
comb	combined.
comp	composite value.
cor	corrected quantity.
dil	dilution air.
dew	dewpoint.
dexh	diluted exhaust.
dry	dry condition.
dutycycle	duty cycle.
∈	related to a difference or error quantity.
exh	raw exhaust.
exp	expected quantity.
fluid	fluid stream.
fn	feedback speed.
frict	friction.
fuel	fuel consumption.
hi,idle	condition at high-idle.
i	an individual of a series.
idle	condition at idle.
in	quantity in.
init	initial quantity, typically before an emission test.
int	intake air.
j	an individual of a series.
mapped	conditions over which an engine can operate.
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.
media	PM sample media.
mix	mixture of diluted exhaust and air.
norm	normalized.
out	quantity out.
P	power.
part	partial quantity.
PDP	positive-displacement pump.
post	after the test interval.
pre	before the test interval.
prod	stoichiometric product.
r	relative (e.g., relative difference or error).
rate	rate (divided by time).
record	record rate.
ref	reference quantity.
rev	revolution.
sat	saturated condition.
s	slip.
span	span quantity.
SSV	subsonic venturi.
std	standard condition.
stroke	engine strokes per power stroke.
T	torque.
test	test quantity.
test,alt	alternate test quantity.
uncor	uncorrected quantity.
vac	vacuum side of the sampling system.
weight	calibration weight.
zero	zero quantity

(f) Constants.

(1) This part uses the following constants for the composition of dry air:

Table 6 of § 1065.1005—Constants

Symbol	Quantity	mol/mol
xγArair	amount of argon in dry air	0.00934
xγCO2air	amount of carbon dioxide in dry air	0.000375
xγN2air	amount of nitrogen in dry air	0.78084
xγO2air	amount of oxygen in dry air	0.209445

(2) This part uses the following molar masses or effective molar masses of chemical species:

Table 7 of § 1065.1005 - Molar —Molar Masses

Symbol	Quantity	g/mol (10-3–3·kg·mol-1–1)
Mair	molar mass of dry air 1	28.96559
MAr	molar mass of argon	39.948
MC	molar mass of carbon	12.0107
MCH3OH	molar mass of methanol	32.04186
MC2H5OH	molar mass of ethanol	46.06844
MC2H4O	molar mass of acetaldehyde	44.05256
MCH4N2O	molar mass of urea	60.05526
MC2H6	molar mass of ethane	30.06904
MC3H8	molar mass of propane	44.09562
MC3H7OH	molar mass of propanol	60.09502
MCO	molar mass of carbon monoxide	28.0101
MCH4	molar mass of methane	16.0425
MCO2	molar mass of carbon dioxide	44.0095
MH	molar mass of atomic hydrogen	1.00794
MH2	molar mass of molecular hydrogen	2.01588
MH2O	molar mass of water	18.01528
MCH2O	molar mass of formaldehyde	30.02598
MHe	molar mass of helium	4.002602
MN	molar mass of atomic nitrogen	14.0067
MN2	molar mass of molecular nitrogen	28.0134
MNH3	molar mass of ammonia	17.03052
MNMHC	effective C1 molar mass of nonmethane hydrocarbon 2	13.875389
MNMHCE	effective C1 molar mass of nonmethane hydrocarbon equivalent 2	13.875389
MNMNEHC	effective C1 molar mass of nonmethane-nonethane hydrocarbon 2	13.875389
MNOx	effective molar mass of oxides of nitrogen 3	46.0055
MN2O	molar mass of nitrous oxide	44.0128
MO	molar mass of atomic oxygen	15.9994
MO2	molar mass of molecular oxygen	31.9988
MS	molar mass of sulfur	32.065
MTHC	effective C1 molar mass of total hydrocarbon 2	13.875389
MTHCE	effective C1 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, NMHCE, and NMNEHC are defined on a C₁ basis and are based on an atomic hydrogen-to-carbon ratio, α, of 1.85 (with β, γ, and δ equal to zero).

³ The effective molar mass of NO_X is defined by the molar mass of nitrogen dioxide, NO₂.

(3) This part uses the following molar gas constant for ideal gases:

Table 8 of § 1065.1005—Molar Gas Constant for Ideal Gases

Symbol	Quantity	J/(mol · Kmol·K) (m2 · kg · s−2 · mol−1 · K−1·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:

Table 9 of § 1065.1005—Ratios of Specific Heats for Dilution Air and Diluted Exhaust

Symbol	Quantity	[J/(kg · Kkg·K)]/[J/(kg · Kkg·K)]
γair	ratio of specific heats for intake air or dilution air	1.399
γdil	ratio of specific heats for diluted exhaust	1.399
γexh	ratio of specific heats for raw exhaust	1.385

(g) Other acronyms and abbreviations. This part uses the following additional abbreviations and acronyms:

Table 10 of § 1065.1005 - Other —Other Acronyms and Abbreviations

Acronym	Meaning
ABS	acrylonitrile-butadiene-styrene.
ASTM	ASTM International.
BMD	bag mini-diluter.
BSFC	brake-specific fuel consumption.
CARB	California Air Resources Board.
CFR	Code of Federal Regulations.
CFV	critical-flow venturi.
CI	compression-ignition.
CITT	Curb Idle Transmission Torque.
CLD	chemiluminescent detector.
CVS	constant-volume sampler.
DEF	diesel exhaust fluid.
DF	deterioration factor.
ECM	electronic control module.
EFC	electronic flow control.
e.g.	exempli gratia, for example.
EGR	exhaust gas recirculation.
EPA	Environmental Protection Agency.
FEL	Family Emission Limit.
FID	flame-ionization detector.
FTIR	Fourier transform infrared.
GC	gas chromatograph.
GC-ECD	GC–ECD	gas chromatograph with an electron-capture detector.
GC-FID	GC–FID	gas chromatograph with a flame ionization detector.
HEPA	high-efficiency particulate air.
IBP	initial boiling point.
IBR	incorporated by reference.
i.e.	id est, in other words.
ISO	International Organization for Standardization.
LPG	liquefied petroleum gas.
MPD	magnetopneumatic detection.
NDIR	nondispersive infrared.
NDUV	nondispersive ultraviolet.
NIST	National Institute for Standards and Technology.
NMC	nonmethane cutter.
PDP	positive-displacement pump.
PEMS	portable emission measurement system.
PFD	partial-flow dilution.
PLOT	porous layer open tubular.
PMD	paramagnetic detection.
PMP	Polymethylpentene.
pt.	a single point at the mean value expected at the standard.
psi	pounds per square inch.
PTFE	polytetrafluoroethylene (commonly known as TeflonTM).
RE	rounding error.
RESS	rechargeable energy storage system.
RFPF	response factor penetration fraction.
RMC	ramped-modal cycle.
rms	root-mean square.
RTD	resistive temperature detector.
SAW	surface acoustic wave.
SEE	standard error of the estimate.
SSV	subsonic venturi.
SI	spark-ignition.
THC-FID	THC–FID	total hydrocarbon flame ionization detector.
TINV	inverse student t-test function in Microsoft Excel.
UCL	upper confidence limit.
UFM	ultrasonic flow meter.
U.S.C.	United States Code

[79 FR 23815, Apr. 28, 2014, as amended at 81 FR 74191, Oct. 25, 2016; 86 FR 34575, June 29, 2021; 87 FR 64866, Oct. 26, 2022; 88 FR 4689, Jan. 24, 2023]