  The colliding wind binary (CWB) systems \eta\ Carinae and WR140 provide
unique laboratories for X-ray astrophysics. Their wind-wind collisions produce
hard X-rays that have been monitored extensively by several X-ray telescopes,
including RXTE. To interpret these X-ray light curves and spectra, we apply 3D
hydrodynamic simulations of the wind-wind collision using smoothed particle
hydrodynamics (SPH), with the recent improvements of radiative cooling and the
acceleration of the stellar winds according to a \beta\ law. For both systems,
the 2-10 keV RXTE light curves are well-reproduced in absolute units for most
phases, but the light curve dips associated with the periastron passages are
not well matched. In WR140, the dip is too weak, and in \eta\ Carinae, the
large difference in wind speeds of the two stars leads to a hot,
post-periastron bubble that produces excess emission toward the end of the
X-ray minimum.
