  We present constraints on theoretical models of Type Ia SNe using spatially
resolved ASCA X-ray spectroscopy of four galaxy clusters: Abell 496, Abell
2199, Abell 3571 & Perseus. All four clusters have central Fe abundance
enhancements and an ensemble of abundance ratios are used to show that most of
the Fe in the central regions of the clusters comes from SN Ia. At the center
of each cluster, simultaneous analysis of spectra from all ASCA instruments
shows that the Ni to Fe abundance ratio (normalized by the solar ratio) is ~ 4.
We use the Ni/Fe ratio as a discriminator between SN Ia explosion models: the
Ni/Fe ratio of ejecta from the "Convective Deflagration" model W7 is consistent
with the observations, while those of "delayed detonation" models are not
consistent at the 90% confidence level.
