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:
Table 2 to § 1036.805 - Symbols for Quantities
Symbol | Quantity | Unit | Unit symbol |
Unit in terms of SI base units |
---|---|---|---|---|
α | atomic hydrogen-to-carbon ratio | mole per mole | mol/mol | 1. |
Α | Area | square meter | m2 | m2. |
β | atomic oxygen-to-carbon ratio | mole per mole | mol/mol | 1. |
C d Α | drag area | meter squared | m2 | m2. |
C rr | coefficient of rolling resistance | kilogram per metric ton | kg/tonne | 10−3. |
D | distance | miles or meters | mi or m | m. |
ε | efficiency | |||
∈ | Difference or error quantity | |||
e | mass weighted emission result | grams/ton-mile | g/ton-mi | g/kg-km. |
Eff | efficiency | |||
E m | mass-specific net energy content | megajoules/kilogram | MJ/kg | m2·s−2. |
f n | angular speed (shaft) | revolutions per minute | r/min | π·30·s−1. |
g | gravitational acceleration | meters per second squared | m/s2 | m·s−2. |
i | indexing variable | |||
k a | drive axle ratio | 1. | ||
k topgear | 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. |
M rotating | inertial mass of rotating components | kilogram | kg | kg. |
N | total number in a series | |||
P | Power | kilowatt | kW | 103·m2·kg·s−3. |
ρ | mass density | kilogram per cubic meter | kg/m3 | m−3·kg. |
r | tire radius | meter | m | m. |
SEE | standard error of the estimate | |||
σ | standard deviation | |||
T | torque (moment of force) | newton meter | N·m | m2·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·m2·kg·s−1. |
w C | carbon mass fraction | gram/gram | g/g | 1. |
w CH4N2O | urea mass fraction | gram/gram | g/g | 1. |
x | amount of substance mole fraction | mole per mole | mol/mol | 1. |
x b | brake energy fraction | |||
x bl | brake energy limit |
(c) Superscripts. This part uses the following superscripts for modifying quantity symbols:
Table 3 to § 1036.805 - Superscripts
Superscript | Meaning |
---|---|
overbar (such as ȳ) | arithmetic mean. |
overdot (such as ẏ) | quantity per unit time. |
(d) Subscripts. This part uses the following subscripts for modifying quantity symbols:
Table 4 to § 1036.805 - Subscripts
Subscript | Meaning |
---|---|
65 | 65 miles per hour. |
A | A speed. |
A | absolute (e.g., absolute difference or error). |
Acc | accessory. |
App | approved. |
Axle | axle. |
B | B speed. |
C | C speed. |
C | carbon mass. |
Ccombdry | carbon from fuel per mole of dry exhaust. |
CD | charge-depleting. |
CO2DEF | CO2 resulting from diesel exhaust fluid decomposition. |
comb | combustion. |
comp | composite. |
Cor | corrected. |
CS | charge-sustaining. |
Cycle | test cycle. |
DEF | diesel exhaust fluid. |
engine | engine. |
Exh | raw exhaust. |
Front | frontal. |
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. |
R | relative (e.g., relative difference or error). |
Rate | rate (divided by time). |
Rated | rated. |
record | record. |
Ref | reference quantity. |
speed | speed. |
Stall | stall. |
Test | test. |
Tire | tire. |
transient | transient. |
Μ | vector. |
vehicle | vehicle. |
(e) Other acronyms and abbreviations. This part uses the following additional abbreviations and acronyms:
Table 5 to § 1036.805 - Other Acronyms and Abbreviations
Acronym | Meaning |
---|---|
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. |
COV | coefficient of variation. |
CS | charge-sustaining. |
DEF | diesel exhaust fluid. |
DF | deterioration factor. |
DOT | Department of Transportation. |
E85 | gasoline blend including nominally 85 percent denatured ethanol. |
ECU | Electronic Control Unit. |
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. |
HDV | heavy-duty vehicle. |
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. |
SCR | selective catalytic reduction. |
SEE | standard error of the estimate. |
SET | Supplemental Emission Test. |
SI | spark-ignition. |
U.S. | United States. |
U.S.C. | United States Code. |
(f) Constants. This part uses the following constants:
Table 6 to § 1036.805 - Constants
Symbol | Quantity | Value |
---|---|---|
g | gravitational constant | 9.80665 m·s−2 |
(g) Prefixes. This part uses the following prefixes to define a quantity:
Table 7 to § 1036.805 - Prefixes
Symbol | Quantity | Value |
---|---|---|
µ | micro | 10−6 |
m | milli | 10−3 |
c | centi | 10−2 |
k | kilo | 103 |
M | mega | 106 |
[81 FR 74011, Oct. 25, 2016; 82 FR 29761, June 30, 2017; 86 FR 34404, June 29, 2021]