Why is my dvd burner burning so slow?

I just switched from a 8x speed burner to a 32x speed burner. When burning a dvd, the encoding part takes about the same amount of time (1-2 hours). When I put the video image on a blank dvd, the 8x burner takes about 20 minutes. But the problem is that the 32x burner takes up to 6 hours and cannot understand why. I am using the right blank dvd's (for the 8x burner i used Verbatim 1x-8x dvd+r and for the 32x burner i use Sony 1x-16x dvd+r). I had someone install this for me but cannot give me a legit answer of what's going on. I want to know how to speed up the burning. I am ok with the encoding part. I am still using the same software roxio and dvd shrink and it should not be the problem because i used it before eventhough nero was recently installed. I also had my virus protection on but i did it before with 8x speed burner. When I burn a dvd i set the speed to 16x to match the speed of my blank dvd.