For each participating engine family, emission credits (positive or negative) are to be calculated according to the following equation and rounded, in accordance with ASTM E29-93a, to the nearest gram. ASTM E29-93a has been incorporated by reference. See Sec. 91.6. Consistent units are to be used throughout the equation. The following equation is used to determine the credit status for an engine family whether generating positive or negative in-use emission credits: [GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT] Where: S(t)=cumulative fraction survived at time t;[mu]life=average useful life in years, specific to the power
rating and the application as given below.
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Power = the average power of an engine family in kW (sales weighted).
The power of each configuration is the rated output in
kilowatts as determined by SAE J1228. This procedure has been
incorporated by reference. See Sec. 91.6.t = time in model yearsmax useful life = maximum useful life specific to the power rating and
the application; max useful life = 2[mu]lifesales = the number of eligible sales tracked to the point of first
retail sale in the U.S. for the given engine family during the
model year.FEL = the family emission limit for the engine family in grams per
kilowatt hour.CL = compliance level of the in-use testing in g/kW-hr.[mu]use = mean use in hours per year. For outboard engines,
[mu]use=34.8 hrs /yr. For personal watercraft,
[mu]use=77.3 hrs/yr;AF = adjustment factor for the number of tests conducted No. eng. tested......................... 2 *, 4 6 8 10Adjustment factor....................... .5 .75 .9 1\*\ Small volume manufacturer