[en] From a previous analysis of UA1 MIMI data at C.M.S. energy of 630 GeV exhibiting a new correlation between the average transverse momentum < p_t> and the central pseudo-rapidity density, we have pointed out a tendency to higher inelasticity via the increase of the transverse mass. More recent results obtained at Fermilab at the same energy (charged pseudo-rapidity measured up to 5.5 units of rapidity) suggest a more important scaling violation in fragmentation region that it was expected previously. The pseudo rapidity distributions observed (also at CMS energy of 1800 GeV) can be reproduced correctly by the generators, if we extend the dynamical range of the coloured strings stretched between valence quarks and diquarks; the net result of this extension is an increase of the total inelasticity in p-p collisions from 0.5 to about 0.7 in the energy decade 0.2 PeV-2 PeV