In step 4 the correction to the energy is determined. The lumped equations are solved and the solution is stored in field v(0,*) (routine resultst.f). No boundary conditions are applied, since the (static) temperature is not known at this point. Step 4 is only performed for gases (which exhibit a strong coupling of density, temperature and pressure) and for liquids for which initial temperature conditions have been defined. In general the coupling in liquids is rather weak.