86.1341-90—Test cycle validation criteria.
(a)
To minimize the biasing effect of the time lag between the feedback and reference cycle values, the entire engine speed and torque feedback signal sequence may be advanced or delayed in time with respect to the reference speed and torque sequence. If the feedback signals are shifted, both speed and torque must be shifted the same amount in the same direction.
(b) Brake horsepower-hour calculation.
(1)
Calculate the brake horsepower-hour for each pair of engine feedback speed and torque values recorded. Also calculate the reference brake horsepower-hour for each pair of engine speed and torque reference values. Calculations shall be to five significant digits.
(2)
In integrating the reference and the feedback horsepower-hour, all negative torque values shall be set equal to zero and included. If integration is performed at a frequency of less than 5 Hz, and if during a given time segment, the torque value changes from positive to negative or negative to positive, then the negative portion must be computed by linear interpolation and set equal to zero and the positive portion included. The same methodology shall be used for integrating both reference and actual brake horsepower-hour.
(c) Regression line analysis to calculate validation statistics.
(1)
Linear regressions of feedback value on reference value shall be performed for speed, torque and brake horsepower on 1 Hz data after the feedback shift has occurred (see paragraph (a) of this section). The method of least squares shall be used, with the best fit equation having the form:
y=mx b
Where:
y = The feedback (actual) value of speed (rpm), torque (ft-lbs), or brake horsepower.
m = Slope of the regression line.
x = The reference value (speed, torque, or brake horsepower).
b = The y-intercept of the regression line.
(2)
The standard error of estimate (SE) of y on x and the coefficient of determination (r 2) shall be calculated for each regression line.
(3)
For a test to be considered valid, the criteria in Figure N90-11 must be met for both cold and hot cycles individually. Point deletions from the regression analyses are permitted where noted in Figure N90-11.
| Speed | Torque | BHP | |
|---|---|---|---|
| Regression Line Tolerances | |||
| Petroleum-fueled and methanol-fueled diesel engines | |||
| Standard error of estimate (SE) of Y on X | 100 rpm | 13 pct. of power map maximum engine torque | 8 pct. of power map maximum BHP. |
| Slope of the regression line, m | 0.970 to 1.030 | 0.83-1.03 (hot), 0.77-1.03 (cold) | 0.89-1.03 (hot), 0.87-1.03 (cold). |
| Coefficient of determination, r 2 | 1 0.9700 | 1 0.8800 (hot), 1 0.8500 (cold) | 1 0.9100. |
| Y intercept of the regression line, b | 50 rpm | 15 ft-lb | 5.0 |
| Gasoline-fueled and methanol-fueled Otto-cycle engines | |||
| Standard error of estimate (SE) of Y on X | 100 rpm | 10% (hot), 11% (cold) of power map max. engine torque | 5% (hot), 6% (cold) of power map maximum BHP. |
| Slope of the regression line, m | 0.980 to 1.020 | 0.92-1.03 (hot), 0.88-1.03 (cold) | 0.93-1.03 (hot), 0.89-1.03 (cold). |
| Coefficient of determination, r 2 | 1 0.9700 | 1 0.9300 (hot), 1 0.9000 (cold) | 1 0.9400 (hot), 1 0.9300 (cold). |
| Y intercept of the regression line, b | 25 (hot), 40 (cold) | 4%(hot), 5 (cold) of power map max. engine torque | 2.0% (hot), 2.5% (cold) of power map BHP. |
| 1 Minimum. | |||
| Condition | Points to be deleted |
|---|---|
| 1. Wide Open Throttle and Torque Feedback < Torque Reference | Torque, and/or BHP. |
| 2. Closed Throttle, Not an Idle Point, Torque Feedback >Torque Reference | Torque, and/or BHP. |
| 3. Closed Throttle, Idle Point, and Torque Feedback = CITT (10 ft-lb) | Speed, and/or BHP. |
| For the purposes of this discussion: | |
| An Idle Point is defined as a point having a Normalized Reference Torque of 0 and a Normalized Reference Speed of 0 and an engine tested as having a manual transmission has a CITT of 0. Point deletion may be applied either to the whole or to any part of the cycle. EXPSTB='00' |
(4)
(i)
For petroleum-fueled and methanol-fueled diesel engines, the integrated brake horsepower-hour for each cycle (cold and hot start) shall be between −15 percent and 5 percent of the integrated brake horsepower-hour for the reference cycle, or the test is void.
(ii)
For gasoline-fueled and methanol-fueled Otto-cycle engines, the integrated brake horsepower-hour of the feedback cycle shall be within 5 percent of the integrated brake horsepower-hour of the reference cycle for the cold cycle, or the test is void. The tolerance for the hot cycle shall be 4 percent.
(5)
If a dynamometer test run is determined to be statistically or experimentally void, corrective action shall be taken. The engine shall then be allowed to cool (naturally or forced) and the dynamometer test rerun per § 86.1337 or be restarted at § 86.1336-84(e).
(d)
For petroleum-fueled and methanol-fueled diesel engines, all reference torque values specified (in paragraph (f)(2) of appendix I to this part) as “closed throttle” shall be deleted from the calculation of cycle torque and power validation statistics.