Document ID: chunk:federal_register_of_legislation:F2011C00805:reg:21:p6
Version: federal_register_of_legislation:F2011C00805
Segment Type: reg
Provision Reference: reg 21 (pt 6/7)
Character Range: 232594–235602

appropriate manner.

           5.  METHODS

           5.1.  Energy variation during coast-down method

           5.1.1. On the road

           5.1.1.1. Test equipment and error

           Time shall be measured to an error lower than  0.1 s.
           Speed shall be measured to an error lower than  2 per cent.

           5.1.1.2.  Test procedure

           5.1.1.2.1. Accelerate the vehicle to a speed 10 km/h greater than the chosen test speed V.

           5.1.1.2.2.  Place the gearbox in 'neutral' position

           5.1.1.2.3.  Measure the time taken (t1) for the vehicle to decelerate from speed

V2 = V + ΔV   km/h   to   V1 = V - ΔV   km/h

           5.1.1.2.4.  Perform the same test in the opposite direction: t2

           5.1.1.2.5.  Take the average T of the two times t1 – t2

           5.1.1.2.6.  Repeat these tests several times such that the statistical accuracy (p) of the average

   is not more than 2 per cent (p  2 per cent)

           The statistical accuracy (p) is defined by:
           where:

           t = coefficient given by the table below,

           n = number of tests,

                                     s = standard deviation,

n  4    5     6     7     8     9     10    11    12    13    14    15

t  3.2  2.8   2.6   2.5   2.4   2.3   2.3   2.2   2.2   2.2   2.2   2.2

   1.6  1.25  1.06  0.94  0.85  0.77  0.73  0.66  0.64  0.61  0.59  0.57

           5.1.1.2.7. Calculate the power by the formula:

           where:

           P is expressed in kW,

           V = speed of the test in m/s,

           ΔV = speed deviation from speed V, in m/s.

           M = reference mass in kg,

           T = time in seconds (s).

           5.1.1.2.8. The power (P) determined on the track shall be corrected to the reference ambient conditions as follows:

 PCorrected  =  K . PMeasured

           where:

                 RR = rolling resistance at speed V
                 RAERO   = aerodynamic drag at speed V
                 RT = total driving resistance = RR + RAERO
                 KR = temperature correction factor of rolling resistance, taken to be equal to: 8.64 A 10-3/C, or the manufacturer's correction factor that is approved by the authority
                 t = road test ambient temperature in C
                 t0 = reference ambient temperature = 20 C
                 ρ = air density at the test conditions
                 ρ0 = air density at the reference conditions
                  (20 C, 100 kPa)

           The ratios RR/RT and RAERO/RT shall be specified by the vehicle manufacturer based on the data normally available to the company.

           If these values are not available, subject to the agreement of the manufacturer and the technical service concerned, the figures for the rolling/ total resistance given by the following formula may be used:

 where:

 M = vehicle mass in kg,

and for each speed the coefficients a and b are shown in the following table:

V (km/h)  a            b