  We systematically explore zero impact parameter collisions of white dwarfs
with the Eulerian adaptive grid code FLASH for 0.64+0.64 M$_{\odot}$ and
0.81+0.81 M$_{\odot}$ mass pairings. Our models span a range of effective
linear spatial resolutions from 5.2$\times10^{7}$ to 1.2$\times10^{7}$ cm.
However, even the highest resolution models do not quite achieve strict
numerical convergence, due to the challenge of properly resolving small-scale
burning and energy transport. The lack of strict numerical convergence from
these idealized configurations suggest that quantitative predictions of the
ejected elemental abundances that are generated by binary white dwarf collision
and merger simulations should be viewed with caution. Nevertheless, the
convergence trends do allow some patterns to be discerned. We find that the
0.64+0.64 M$_{\odot}$ head-on collision model produces 0.32 M$_{\odot}$ of
\nickel[56] and 0.38 M$_{\odot}$ of \silicon[28], while the 0.81+0.81
M$_{\odot}$ head-on collision model produces 0.39 M$_{\odot}$ of \nickel[56]
and 0.55 M$_{\odot}$ of \silicon[28] at the highest spatial resolutions. Both
mass pairings produce $\sim$0.2 M$_{\odot}$ of unburned
\carbon[12]+\oxygen[16]. We also find the 0.64+0.64 M$_{\odot}$ head-on
collision begins carbon burning in the central region of the stalled shock
between the two white dwarfs, while the more energetic \hbox{0.81+0.81
M$_{\odot}$} head-on collision raises the initial post-shock temperature enough
to burn the entire stalled shock region to nuclear statistical equilibrium.
