  In order to improve simulations with domain wall fermions (DWFs), it has been
suggested to project out a number of low-lying eigenvalues of the 4-dimensional
Dirac operator that generates the transfer matrix of DWF. We investigate how
this projection method affects chiral properties of quenched DWF. In
particular, we study the behaviour of the residual mass as a function of the
size of the extra dimension.
