4. Mr Martini concluded from the evidence presented that the VPR system is not suitable for measurements with D₅₀ < 23nm. However, the question of measuring during an active regeneration remains.

5. Given that for current GDI, it is shown that there is not a big difference between the particle emissions from GDI compared to diesels; the group discussion preliminary conclusions were that there is no clear driver to extend the D₅₀ to below 23 nm.

6. PMP group concluded that there is no justification for extending the D₅₀ to below 23 nm for diesels. Jürgen Stein reminded the group that higher injection pressures do not lead to the decreased size of the particles as is often feared.

7. Ms. Hosier wondered if the nucleation mode solid particles exist but are not independent of the accumulation mode and there are no separate or additional control technologies – does it make sense to regulate.

8. Mr. Stein (ACEA / EUROMOT) noted that industry has invested millions on the equipment and yet still today there is not a really good calibration procedure existing – therefore major focus should be on improving calibration on existing systems.

9. Reproducibility / repeatability questions need to be considered as the increase in uncertainty of measurement from reducing the D₅₀ would need to be compensated in the limit values.

10. Additives in fuel – for Europe not a big deal – but fuel borne cat additive only in conjunction with DPF.

11. Ms. Karlsson noted that it would be more productive to spend the time on improving calibration rather than chasing the extreme circumstances.

12. JRC agreed that we might be talking only about non DPF vehicles and extreme lubricants.

13. The discussion will continue at the next PMP meeting and focus on what elements need to be provided to the legislators to support policy decision making.

• Information on nature of the particles: Are the particles even real? Do they originate upstream or down stream of PF (particle filter)? If they come from downstream of the PF, then attention is needed, however the current review dosen’t support this assumption……
• Health effects depend on what’s in the particles.
• It makes sense only if relevant for human health and independent from accumulation mode already measured.
• What can we do about them if they exist? Feasibility to measure – reproducibility – changing the system ….

14. Jürgen Stein recommended to show the presentation and the ‘unknowns’ and clearly identifying where further investigations are required.

15. Mr. Andersson noted that it’s extremely clear from the JRC literature study that it is not possible to measure below 10nm. He recommended that with CVS need to stay at 23nm, with further research for a D₅₀ between 10 and 23nm.