Recording speed is determined not only by the drive’s speed capability but by the quality of the media you use. Writeable DVD’s are rated according to the maximum speed at which data can be written to the disk reliably. In fact, some DVD writing software attempts to determine the speed rating of the disk in the drive and adjusts the write speed accordingly. I’m not sure if Nero does this or not. The speed ratings of DVD writeable disks is not as ambiguous as CD’s. For the most part, you cannot reliably write to a DVD at speeds greater than it’s rated speed.
My suggestion is to buy a small sample of disks rated for 4X or 8X writing to see if the drive jumps up to it’s maximum rated speed. Also, be sure your software is not set to limit writing speed. Set to ‘Max,’ it should write to the disk as fast as the disk is capable of reliably writing data.
Hope this helps.