The BenQ 1655 can overburn DVD+R media, and the amount varies with media from approx. 4550-4700 MB with around 4600 MB being common.
I haven't seen anyone trying to overburn DVD+RW media, so you probably have to find this out yourself.
There's a thread on overburning with the BenQ 1655/1650:
BenQ DW1655/DW1650 overburning thread