  It has been shown that the rate of angular momentum loss (AML) in cataclysmic
variables (CVs) below the period gap is about 2.47 times that caused by
gravitational radiation, suggesting extra AML mechanism besides gravitational
radiation. Several potential mechanisms have been proposed but none of them has
been verified. In this work we examine whether AML caused by friction between
the expanding nova envelope and the donor star can account for the required AML
rate. By adopting various expanding velocities of the envelope, we have
calculated the evolution of CVs with typical initial parameters. Our results
show that this friction interaction unlikely solve the extra AML problem unless
the expanding velocities are extremely low. Thus there should be a more
efficient AML mechanism that plays a role in the CV evolution.
