# 40 CFR 86.345-79 - Emission calculations.

α = atomic hydrogen/carbon ratio of the fuel

φ = dry fuel-air ratio (measured)/fuel-air ratio (stoichiometric)

*BARO*= Barometric pressure (in.

*H*g

*A*)

*BHP*= Brake horsepower

*BSCO*= Brake specific carbon monoxide emissions, (gm/

*BHP-HR)*

*BSFC*= Brake specific fuel consumption (lb/

*BHP-HR*)

*BSHC*= Brake specific hydrocarbon emissions (gm/

*BHP-HR*)

*BSNO*

*X*= Brake specific oxides of nitrogen emissions (gm/

*BHP-HR*)

*DCO*= CO volume concentration in exhaust, ppm (dry)

*DCO*

*2*= CO

*2*volume concentration in exhaust, percent (dry)

*DHC*= HC volume carbon concentration in exhaust, ppmC (dry)

*DKNO*= NO volume concentration in exhaust, in ppm (dry and humidity corrected)

*EIP*= engine intake pressure (in.

*H*g

*A*) =

*BARO*− inlet depression

*f/a*= measured dry fuel-air ratio

*G*= humidity of the inlet air in grains of water per pound of dry air = (453.59/0.0648)

*H*, (see § 86.344)

*K*= water − gas equilibrium constant = 3.5

*K*

*NOx*= Humidity correction factor for oxides of nitrogen

*K*

*w*= Wet to dry correction factor

*M*

*C*= Atomic weight of carbon

(

*M**C**M**H*) = mean molecular weight of the fuel per carbon atom*M*

*CO*= Molecular weight of CO

*M*

*F*= Mass flow-rate of fuel used in the engine in lb/hr =

*W*

*f*/453.59

*M*

*H*= Atomic weight of hydrogen

*M*

*NO*

*2*= Molecular weight of nitrogen dioxide (NO

*2*)

*T*= Temperature of inlet air (°F)

*W*

*CO*= Mass rate of CO in exhaust, grams/hr

*W*

*f*= Mass flow-rate of fuel used in the engine, in grams/hr = (453.59)×(

*W*

*f*lbs/hr)

*WHC*= HC volume concentration in exhaust, ppm

*C*(wet)

*W*

*HC*= Mass rate of HC in exhaust, grams/hr

*W*

*NOx*= Mass rate of NO

*X*in exhaust, grams/hr

Dry concentrations = 1/

*K**W*×wet concentrations.*K**W*is defined by the equation in Figure D79-6.
(2)
For Diesel engines, for each mode use the measured engine (

*f/a*) entering the combustion chamber when calculating φ. If applicable bleed air, etc. must be subtracted from the measured air flow (see § 86.313).
(3)
For gasoline-fueled engines, optional for Diesel engines, calculate φ for each mode by substituting

*WHC*for*DHC*in the (*f/a*) equations in paragraph (d) of this section.
(4)
Calculate a

*Y*value for each gasoline-fueled engine test from the pre-test data. Apply the*Y*value to the*K**W*equation for the entire test.
(5)
Calculate a separate

*Y*value for each Diesel test segment from the pretest-segment data. Apply the*Y*value to the*K**W*equation for the entire test-segment.Where

(1)

*Diesel engines only.*Compare the calculated dry (*f/a*) with the measured fuel and air flow. For a valid test the emission calculated (*f/a*) must agree within 10 percent of the measured (*f/a*) for each mode. Diesel engine idle and 2 percent modes do not have to meet this requirement.
(2)

*Fuel/Air ratio comparison.*When comparing measured (*f/a*) ratio to an emissions calculated (*f/a*) ratio, the measured air flow (in terms of mass) is the total mass of air entering the exhaust pipe. This may include additions of air mass to the exhaust pipe by an air injection system.
(3)
Other methods of data validation may be used if prior approval is obtained from the Administrator.

(4)
Data validation techniques that have obtained prior approval from the Administrator for use on gasoline-fueled engines may be used to determine void tests.

(f)
Multiply the dry nitric oxide volume concentrations by the following humidity correction factor to obtain

*DKNO:**K*

*NOx*0.6272 = 0.00629G − 0.0000176G

^{2}

where:

*A =*0.044 (

*f/a*) − 0.0038

*B*= − 0.116(

*f/a)*0.0053

*T*= Temperature of inlet air, °F.

(1)
For gasoline-fueled engines, weight the mass values of

*BHIP, W**HC**, W**CO**, Mf*, and*W**NOx*for each mode by multiplying the modal mass values by the appropriate modal weighting factor prescribed by § 86.335.
(2)
Each Diesel engine test by summing the weighted values (

*BHP, W**HC*,*W**CO*, and*W**NOx*) from each mode as follows:(

*t*) = Test cycle number (*t*= 1, 2) (gasoline-fueled engines only).
(1)
Calculate the brake-specific fuel consumption (

*BSFC*) from the nonweighted*BHP*and*Mf*for each mode. Gasoline-fueled engine idle and*CT*modes, and Diesel idle modes are excluded.where:

(4)
Other methods of correcting power to determine

*BSFC*may be used only with prior approval of the Administrator.where:

*t*= Test cycle number (

*t*= 1,2)

(l)
For gasoline-fueled engines, calculate the brake-specific emissions and fuel consumption for the complete test as follows:

*BSHC(T) =*0.35

*BSHC*(1) = 0.65

*BSHC*(2)

*BSCO(T) =*0.35

*BSCO*(1) = 0.65

*BSCO*(2)

*BSNO*

*x*(

*T*) = 0.35

*BSNO*

*x*(1) = 0.65

*BSNO*

*x*(2)

*WBSFC(T) =*0.35

*WBSFC*(1) = 0.65

*WBSFC*(2)

**Title 40 published on 2013-07-01**

no entries appear in the Federal Register **after** this date.