An estimation of the effect of gear transmission ratio variations on CO2 emissions from conventional vehicles over WLTP Alessandro Marotta, Giorgos Fontaras, Biagio Ciuffo JRC

Objective: estimate the effect of GB differences on CO2 emissions for WLTP TA interpolation method purposes The current TA procedure allows the extension of the TA from one vehicle to another having a different transmission ratios, under given conditions: [from Commission Regulation (EC) 692/2008]

In order to see whether this same extension concept and limit could be applied to the WLTP interpolation method for type approval, JRC has been requested to carry out some simulations. Simulation framework: A generic gasoline vehicle with a baseline GB and 5 alternative, realistic GB (all with 6 gears) A generic diesel vehicle with a baseline GB and 9 alternative, realistic GB (all with 6 gears) Simulations with a JRC model, based on AVL Cruise and Heinz Steven’s Gear Shift Tool (JRC implementation of version 1a)

Gasoline Vehicle: inputs and results (1) gb_finaldrgb_gr1gb_gr2gb_gr3gb_gr4gb_gr5gb_gr a b % b/a98.8%101.9%93.7%93.8%97.4%96.6% c % c/a96.4%92.3%93.9%92.4%93.7%92.1% d % d/a100.9% 96.6%96.9%103.2%104.4% e % e/a96.2%95.8%95.9%96.2%96.7%98.3% f % f/a103.2%103.3%98.9%99.2%105.6%109.6% CO2_WLTP

Gasoline Vehicle: inputs and results (2) gb_finaldrgb_gr1gb_gr2gb_gr3gb_gr4gb_gr5gb_gr CO2_WLTP a b % b/a98.8%101.9%93.7%93.8%97.4%96.6% c % c/a96.4%92.3%93.9%92.4%93.7%92.1% d % d/a100.9% 96.6%96.9%103.2%104.4% e % e/a96.2%95.8%95.9%96.2%96.7%98.3% f % f/a103.2%103.3%98.9%99.2%105.6%109.6%

Diesel Vehicle: inputs and results (1) gb_finaldrgb_gr1gb_gr2gb_gr3gb_gr4gb_gr5gb_gr CO2_WLTP

Diesel Vehicle: inputs and results (2) gb_finaldrgb_gr1gb_gr2gb_gr3gb_gr4gb_gr5gb_gr CO2_WLTP

Conclusion and suggestions Gasoline vehicles appear to be more sensitive to gear transmission variations than diesel vehicles. For transmission variations up to 8% (as defined in Commission Regulation 692/2008) the effects on CO2 emissions from gasoline vehicles can be up to 2%, while for diesel vehicles the variations seem to stay below 0.5%. On the basis of this exercise it does not appear advisable to keep the E≤8% variation limit also for the WLTP interpolation method. Two alternatives (example*): One single limit of E≤4% for all vehicles A limit of E≤4% for gasoline vehicles and E≤8% for diesel vehicles * For a more accurate proposal it might be worth to extend the present study