Force growisofs to use lower speed

[T <mlist4suntong@yahoo.com>]

Hi, 

I just replaced my 4X dvd burner with a 16X one, but can't burn my DVD any
more. I was cautious enough to burn my first trial with lower speed, but
growisofs wouldn't allowed me. It still burns at 8X, thus produced a
coaster at the end: 

% nice -n -2 growisofs -speed=4 -dvd-compat -Z /dev/dvd=/tmp/d1.iso
/dev/dvd: "Current Write Speed" is 8.2x1385KBps.
   1605632/4506009600 ( 0.0%) @0.0x, remaining 280:32
:-? the LUN appears to be stuck writing LBA=310h, retry in 70ms
[...]
4491739136/4506009600 (99.7%) @5.8x, remaining 0:01
builtin_dd: 2200208*2KB out @ average 5.4x1385KBps
/dev/dvd: flushing cache
/dev/dvd: closing track
/dev/dvd: closing disc
:-[ CLOSE SESSION failed with SK=2h/ASC=04h/ACQ=07h]: Resource temporarily unavailable

I used "-speed=4", why it didn't work?
Why the growisofs insists to use speed 8 even after I specified "speed 4"? 
Is there any way to burn my dvd at a lower speed? 

thanks 

PS. 

- The DVD media was perfectly fine with my previous (no
longer available) burner.

- The load was around 0.1 when burning and I used "nice -n -2". So it is
not a system load issue. 

- I tried a second time, the load was still around 0.1 when burning and I
still used "nice -n -2". but got another coaster:

4502913024/4506009600 (99.9%) @5.9x, remaining 0:00
builtin_dd: 2200208*2KB out @ average 5.4x1385KBps
/dev/dvd: flushing cache
/dev/dvd: closing track
/dev/dvd: closing disc
:-[ CLOSE SESSION failed with SK=2h/ASC=04h/ACQ=07h]: Resource temporarily unavailable

- Here are the detail info about the DVD drive and media:

$ dvd+rw-mediainfo /dev/dvd 
INQUIRY:                [PIONEER ][DVD-RW  DVR-110D][1.17]
GET [CURRENT] CONFIGURATION:
 Mounted Media:         1Bh, DVD+R
 Media ID:              RITEK/R03
 Current Write Speed:   8.0x1385=11080KB/s
 Write Speed #0:        8.0x1385=11080KB/s
 Write Speed #1:        6.0x1385=8310KB/s
 Write Speed #2:        4.0x1385=5540KB/s
 Speed Descriptor#0:    00/2295103 R@8.0x1385=11080KB/s W@8.0x1385=11080KB/s
 Speed Descriptor#1:    00/2295103 R@6.0x1385=8310KB/s W@6.0x1385=8310KB/s
 Speed Descriptor#2:    00/2295103 R@4.0x1385=5540KB/s W@4.0x1385=5540KB/s
READ DVD STRUCTURE[#0h]:
 Media Book Type:       A1h, DVD+R book [revision 1]
 Legacy lead-out at:    2295104*2KB=4700372992
READ DISC INFORMATION:
 Disc status:           blank
 Number of Sessions:    1
 State of Last Session: empty
 Number of Tracks:      1
READ TRACK INFORMATION[#1]:
 Track State:           blank
 Track Start Address:   0*2KB
 Next Writable Address: 0*2KB
 Free Blocks:           2295104*2KB
 Track Size:            2295104*2KB
READ CAPACITY:          1*2048=2048

thanks for your help