I also have this problem with a LG 16x DVD-RW drive, P4 1.8 Ghz.
Tunning hdparams increased a bit the speed to 2x.
Changing the k3b process priority to 19 increased further the speed to 6x (but it is still far from 16x).
I guess the problem is related to the CPU usage: hdparams reduces CPU usage, and renice gives more CPU to k3b, so both increase the burning speed.
I also have this problem with a LG 16x DVD-RW drive, P4 1.8 Ghz.
Tunning hdparams increased a bit the speed to 2x.
Changing the k3b process priority to 19 increased further the speed to 6x (but it is still far from 16x).
I guess the problem is related to the CPU usage: hdparams reduces CPU usage, and renice gives more CPU to k3b, so both increase the burning speed.