[en] The π⁺ π^- production far below the N-N collision production threshold has been investigated with the ₁₂C beam from the CERN SC and different targets. The results are compared with the prediction of a first N-N collision model. A reasonable agreement is obtained for the ₁₂C+₁₂C π⁺ data at 86 MeV/A. For other targets, the agreement is poor. Systematic deviations are found even with the ₁₂C+₁₂C system at low pion energy. The target dependence of the π⁺ versus π^- production cross section is rather surprising. No explanation for it has been found