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§ 1037.805 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 § 1037.810). 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:
Table 1 to Paragraph (a) of § 1037.805—Symbols for Chemical Species and Exhaust Constituents
| Symbol | Species |
|---|---|
| C | carbon. |
| CH4 | methane. |
| 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. |
| THC | total hydrocarbon. |
| THCE | total hydrocarbon equivalent. |
(b) Symbols for quantities. This part 1037 uses the following symbols and units of measure for various quantities:
Table 2 to Paragraph (b) of § 1037.805—Symbols for Quantities
| Symbol | Quantity | Unit | Unit symbol | Unit in terms of SI base units |
|---|---|---|---|---|
| A | vehicle frictional load | pound force or newton | lbf or N | kg·m·s−2. |
| a | axle position regression coefficient | |||
| α | atomic hydrogen-to-carbon ratio | mole per mole | mol/mol | 1. |
| α | axle position regression coefficient | |||
| α0 | intercept of air speed correction | |||
| α1 | slope of air speed correction | |||
| ag | acceleration of Earth's gravity | meters per second squared | m/s 2 | m·s−2. |
| a0 | intercept of least squares regression | |||
| a1 | slope of least squares regression | |||
| B | vehicle load from drag and rolling resistance | pound force per mile per hour or newton second per meter | lbf/(mi/hr) or N·s/m | kg·s−1. |
| b | axle position regression coefficient | |||
| β | atomic oxygen-to-carbon ratio | mole per mole | mol/mol | 1. |
| β | axle position regression coefficient | |||
| β0 | intercept of air direction correction | |||
| β1 | slope of air direction correction | |||
| C | vehicle-specific aerodynamic effects | pound force per mile per hour squared or newton-second squared per meter squared | lbf/mph 2 or N·s 2/m 2 | kg·m−1. |
| c | axle position regression coefficient | |||
| ci | axle test regression coefficients | |||
| Ci | constant | |||
| ΔCdA | differential drag area | meter squared | m 2 | m 2. |
| CdA | drag area | meter squared | m 2 | m 2. |
| Cd | drag coefficient | |||
| CF | correction factor | |||
| Crr | coefficient of rolling resistance | newton per kilonewton | N/kN | 10−3. |
| D | distance | miles or meters | mi or m | m. |
| e | mass-weighted emission result | grams per ton-mile | g/ton-mi | g/kg-km. |
| Eff | efficiency | |||
| F | adjustment factor | |||
| F | force | pound force or newton | lbf or N | kg·m·s−2. |
| fn | angular speed (shaft) | revolutions per minute | r/min | π·30·s−1. |
| G | road grade | percent | % | 10−2. |
| g | gravitational acceleration | meters per second squared | m/s 2 | m·s−2. |
| h | elevation or height | meters | m | m. |
| i | indexing variable | |||
| ka | drive axle ratio | 1. | ||
| kd | transmission gear ratio | |||
| ktopgear | highest available transmission gear | |||
| L | load over axle | pound force or newton | lbf or N | kg·m·s−2. |
| 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. |
| Me | vehicle effective mass | kilogram | kg | kg. |
| Mrotating | inertial mass of rotating components | kilogram | kg | kg. |
| N | total number in series | |||
| n | number of tires | |||
| n | amount of substance rate | mole per second | mol/s | mol·s−1. |
| P | power | kilowatt | kW | 10 3·m 2·kg·s−3. |
| p | pressure | pascal | Pa | kg·m−1·s−2. |
| ρ | mass density | kilogram per cubic meter | kg/m 3 | kg·m−3. |
| PL | payload | tons | ton | kg. |
| φ | direction | degrees | ° | °. |
| ψ | direction | degrees | ° | °. |
| r | tire radius | meter | m | m. |
| r2 | coefficient of determination | |||
| Re# | Reynolds number | |||
| SEE | standard error of the estimate | |||
| σ | standard deviation | |||
| TRPM | tire revolutions per mile | revolutions per mile | r/mi | |
| TRRL | tire rolling resistance level | newton per kilonewton | N/kN | 10−3. |
| T | absolute temperature | kelvin | K | K. |
| T | Celsius temperature | degree Celsius | °C | K−273.15. |
| T | torque (moment of force) | newton meter | N·m | m 2·kg·s−2. |
| t | time | hour or second | hr or 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 | weighting factor | |||
| w | wind speed | miles per hour | mi/hr | m·s−1. |
| W | work | kilowatt-hour | kW·hr | 3.6·m 2·kg·s−1. |
| wC | carbon mass fraction | gram per gram | g/g | 1. |
| WR | weight reduction | pound mass | lbm | kg. |
| x | amount of substance mole fraction | mole per mole | mol/mol | 1. |