We analyze a precoded and iteratively detected downhink multiuser system employing imperfect Spatio-Temporal Channel Impulse Response at the Transmitters (ST-GIRT) with the aid of Extrinsic Information Transfer (EXIT) charts. A Precoded Iterative DownLink Space Division Multiple Access (PI-DL-SDMA) system proposed in our previous research is further improved and shown to be capable of maintaining an infinites-imally low BER, despite using imperfect ST-CIRT. A further novel feature of the VPI-DL-SDMA system is that we designl an IrRegular Convolutional Code (IRCC) with the aid of EXIT chart analysis for creating an open EXIT tunnel between the inner decoder's and outer decoder's EXIT curve at a reduced E _b /N ₀ value and hence maintain an infinitesimally low BER.