I have developed an IDL simulation of an electron multiplying L3 (low light level) technology CCD that includes the effects of clock induced charge and multiplication noise. This model allows observers interested in obtaining high time resolution photometry and spectroscopy of faint sources to compare more easily the gains in performance that can be expected by switching to an L3 detector. The model has been used to generate synthetic image sequences of stars and emission lines. The stellar images are analysed to show how the measured centroid noise of the star varies with the source brightness. In the case of the synthetic spectra the analysis determines how the SNR of a Gaussian line fit varies with the source brightness. In order to provide points of reference, the results are compared with both an ideal detector and a conventional CCD with various levels of read noise. The results show how closely an L3 CCD can approach to an ideal detector in various observing regimes. The performance of an L3 detector in photon counting mode is also investigated.