Proposal for WLTP Tabulated Load Coefficients. Thomas B. Wagner,

Transcription

1 Proposal for WLTP Tabulated Load Coefficients Thomas B. Wagner,

2 Use of tabulated load coefficients Default load coefficients are used to handle high variety and small series. Today passenger cars (M1) are tested based on road load coefficients these parameters are lower than the default coefficients. Exceptions e.g. Sprinter coaches with 8+1 seats (about 4500 units per year). The default values of light commercial vehicles (N1) and 4x4 drivetrains are 30% higher (factor 1,3). This represents the payload of N1 vehicles. tabulated default values Coast down / road load data 2

3 Multistage vehicles high variety Reference mass = curb weight + default added mass (DAM) calculated by a 2 nd order polynomial function 3

4 Road load coefficients vs. tabulated load F[N] F[N] A 0, A 1, A 2 load adjustment F 0, F 1, F 2, F R, FTS V [km/h] - rolling resistance axles - drivetrain lossess V [km/h] Road load data rolling resistance aerodynamic drag drag torque drivetrain vehicle mass Dynamometer settings Tabulated load default aerodynamic Test Mass Widerstand bei 80 km/h a b c kg kw N N N/(km/h) N/(km/h)² , drag 0, , , , ,0395 losses , , , , , losses 0, , , , , , ,0480 F[N] , , , , , , , , , , ,3F ,0565 0, F 2, F R, FTS , , , , , , , , , , ,8 485 V 69[km/h] 0 0, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,0650 default drivetrain default front axle Road load coefficients are significantly different from tabulated load coefficients. Due to load adjustment dynamometer settings are found. Dynamometer settings + rolling resistance driving axle + drivetrain losses By use of tabulated values there is no load adjustment. Rolling resistance and drivetrain losses are additional. 4

5 Dynamometer 80 km/h [kw] Discussion of different default value proposals WLTP based dynamometer settings and target curve proposals No physical basis recognizable CO2 regulation M1/N1 ends at a reference mass of 2610 kg 2 nd TNO proposal, PSA tab. values WLTP reference mass: M1: Curb weight + 15% payload, N1: curbweight + 35% payload [kg] 5

6 Conclusion There is a discussion initiated on tabulated load settings because of the assumption they don t represent the reality in a appropriate way. This wrong interpretation is supported by wrong statements and analyses. Facts: Passenger cars as well as small and medium vans (M1 + N1) use road load coefficients because the default tabulated settings are worse. In the segment of large vans (M1 + N1) there are a lot of variants, therefore tabulated values are helpful to optimize the homologation complexity. (Examples: 3 roof heights, roof-a/c, different tire types, single and twin axles, different drivetrains, manifold platforms, multistage type approval, ) Today payload of N1 vehicles is represented by an load increase of 30% (factor 1,3). If payload is added to the reference mass, there is no physical basement for this factor anymore. 6

7 Conclusion Today the M1 and N1 CO2-regulation is not exceeding a reference mass of 2610 kg we recommend a discussion about the payload of 35% and the load increase of 30% (factor 1,3). In the available proposals of PSA and Ford (2 nd ) we look for a physical basis to legitimate a polynomial growth with increasing weight and for the jump in the function at 1810 kg. After analysis of the todays tabulated default values we conclude that they represent the vehicle landscape in a appropriate way. The WLTP dynamometer settings large vans, such as Sprinter, are clearly under the 30% curve. Based on our proposed default values we expect a better physical approach than the todays load increase of 30%. We invite you to draw your dynamometer settings of passenger cars and vans in the diagram on slide 5 by using the calculation in the backup. 7

8 Backup

9 Tabulated Load Values (proposal MB Vans) There is no general correlation between aerodynamic resistance and Test mass of the vehicle. So it makes sense to limit the factor c at the worst case of the Large Van categorie The factor c is based on the actual measured aerodynamis cw x A from our Small-, Midsize- and Large Vans. This will be the worst case in the future when the new table values will become effectiv. The Factor a corresponds to the quotient A0 (Coast down test)/f0 (Load adjustment on the test bench). rolling resistance =A0/F0 a = 7 kg/t*9,81*tm/ N vehicle test mass brake losses (nondriving axle) c = 0,5*cw*A*1,2/(3,6²) 9

10 Correlation between table values and road load data Driving resistance at the roller test bench= Resistance of the braked dynamometer (F0, F1, F2) + rolling resistance driving axle (FR) + drivetrain losses: driving axle, joint shaft bearings, gearbox and bearings (FTS) =required engine power With road load data Load adjustment (F0, F1, F2) = Road load data (A0, A1, A2) FR 1 FTS 1 With table values Required engine power= Road load data(a0, A1, A2) = Load adjustment (F0, F1, F2) + FR 1 + FTS 1 Required engine power= Table values (F0, F1, F2) + FR 2 + FTS 2 By using the same car (FR 1 = FR 2 and FTS 1 = FTS 2 ) for measuring with road load data and table values, it is correct to compare load adjustment and table values. FR.. rolling resistance driving axle FTS.. drivetrain losses: driving axle, joint shaft bearings, gearbox and bearings 10

11 Tabulated Load Values (proposal MB Vans) Test Mass Widerstand bei 80 km/h a b c kg kw N N N/(km/h) N/(km/h)² , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,0650 Citan Viano/Vito Successor Sprinter Successor worst case 11

12 History new table values 1. Proposal PSA ( ) Test Mass (TM) Power and load absorbed by the dynamometer at 80 km/h Coefficients a b c Kg kw N N N/(km/h) N/(km/h)² , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0, , ,0 0,1 0,1154 Factor a is much too high, elevated values for rolling resistance and break losses There is no need for a factor b: drive train losses are included on the test bench. Factor c is much too high, and a correlation between weight and aerodynamics is wrong 12

13 History new table values Proposal Ford ( ) Test Mass Widerstand bei 80 km/h a b c kg kw N N N/(km/h) N/(km/h)² , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , These are the old table values (83:06), expanded to higher weights The aerodynamics (factor c) doesn t show the worst-case in the future when the new table values will become effective and has to be updated Factor a becomes smaller with a weight over 3800 kg. This is illogical.

14 History new table values 3. Proposal MB Vans ( ) Test MassWiderstand bei 80 km/h a b c kg kw N N N/(km/h) N/(km/h)² , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,0650 These values are based on actual MB Vans Series, and this will be the worst case at the entry into force of the new table values. 14

15 15 History new table values Proposal Ford ( ) Test Mass Widerstand bei 80 km/h a b c kg kw N N N/(km/h) N/(km/h)² , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,124 This is a combintion of the old table values (83:06), above 1810 kg with multiplication of the factor 1,3