Slow DVD read to SCSI harddrive

I recently installed a new IDE DVD burner (Phillips DVD8801). The previous burner died and was on this system when only SCSI hard drives were installed. I currently have one SCSI drive on one of the motherboards resident Adaptec AIC-7902 Ultra320 SCSI Controllers and one hard drive (Ultra DMA mode 5) set as master with the DVD burner (Ultra DMA mode 2) set as slave on the IDE Controller. When reading a DVD to make an ISO file, I get low (1.8x) reads when writing the ISO file to the SCSI drive. The speeds are much better (8.0x) when writing the ISO from the DVD to the IDE hard drive. Any clues?