Title 40

SECTION 1036.805

1036.805 Symbols, abbreviations, and acronyms.

§ 1036.805 Symbols, abbreviations, and acronyms.

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 (incorporated by reference in § 1036.810). 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 chemical species. This part uses the following symbols for chemical species and exhaust constituents:

Symbol Species
C carbon.
CH4 methane.
CH4N2O urea.
CO carbon monoxide.
CO2 carbon dioxide.
H2O water.
HC hydrocarbon.
NMHC nonmethane hydrocarbon.
NMHCE nonmethane hydrocarbon equivalent.
NO nitric oxide.
NO2 nitrogen dioxide.
NOX oxides of nitrogen.
N2O nitrous oxide.
PM particulate matter.

(b) Symbols for quantities. This part uses the following symbols and units of measure for various quantities:

Symbol Quantity Unit Unit symbol Unit in
terms of
SI base
a atomic hydrogen-to-carbon ratio mole per mole mol/mol 1.
b atomic oxygen-to-carbon ratio mole per mole mol/mol 1.
CdA drag area meter squared m 2 m 2.
Crr coefficient of rolling resistance kilogram per metric ton kg/tonne 10−3.
D distance miles or meters mi or m m.
e mass weighted emission result grams/ton-mile g/ton-mi g/kg-km.
Eff efficiency.
Em mass-specific net energy content megajoules/kilogram MJ/kg m 2·s−2.
fn angular speed (shaft) revolutions per minute r/min π·30·s−1.
i indexing variable.
ka drive axle ratio.
ktopgear highest available transmission gear.
m mass pound mass or kilogram lbm or kg kg.
M molar mass gram per mole g/mol 10−3·kg·mol−1.
M vehicle mass kilogram kg kg.
Mrotating inertial mass of rotating components kilogram kg kg.
N total number in a series.
P power kilowatt kW 10 3·m 2·kg·s−3.
T torque (moment of force) newton meter N·m m 2·kg·s−2.
t time second s s.
Δt time interval, period, 1/frequency second s s.
UF utility factor.
v speed miles per hour or meters per second mi/hr or m/s m·s−1.
W work kilowatt-hour kW·hr 3.6·m 2·kg·s−1.
wC carbon mass fraction gram/gram g/g 1.
wCH4N2O urea mass fraction gram/gram g/g 1.
x amount of substance mole fraction mole per mole mol/mol 1.
xb brake energy fraction.
xbl brake energy limit.

(c) Superscripts. This part uses the following superscripts to define a quantity:

Superscript Quantity
overbar (such as y ) arithmetic mean.
overdot overdot (such as y ) quantity per unit time.

(d) Subscripts. This part uses the following subscripts to define a quantity:

Subscript Quantity
65 65 miles per hour.
A A speed.
acc accessory.
app approved.
axle axle.
B B speed.
C C speed.
Ccombdry carbon from fuel per mole of dry exhaust.
CD charge-depleting.
CO2DEF CO2 resulting from diesel exhaust fluid decomposition.
comb combustion.
cor corrected.
CS charge-sustaining.
cycle test cycle.
DEF diesel exhaust fluid.
engine engine.
exh raw exhaust.
fuel fuel.
H2Oexhaustdry H2O in exhaust per mole of exhaust.
hi high.
i an individual of a series.
idle idle.
m mass.
max maximum.
mapped mapped.
meas measured quantity.
neg negative.
pos positive.
record record.
ref reference quantity.
speed speed.
stall stall.
test test.
tire tire.
transient transient.
vehicle vehicle.

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

ABT averaging, banking, and trading AECD auxiliary emission control device ASTM American Society for Testing and Materials BTU British thermal units CD charge-depleting CFR Code of Federal Regulations CI compression ignition CS charge-sustaining DF deterioration factor DOT Department of Transportation E85 gasoline blend including nominally 85 percent denatured ethanol EPA Environmental Protection Agency FCL Family Certification Level FEL Family Emission Limit GEM Greenhouse gas Emissions Model g/hp-hr grams per brake horsepower-hour GVWR gross vehicle weight rating LPG liquefied petroleum gas NARA National Archives and Records Administration NHTSA National Highway Traffic Safety Administration NTE not-to-exceed RESS rechargeable energy storage system RMC ramped-modal cycle rpm revolutions per minute SCR Selective catalytic reduction SI spark ignition U.S. United States U.S.C. United States Code

(f) 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 10 3
M mega 10 6
[81 FR 74011, Oct. 25, 2016; 82 FR 29761, June 30, 2017]