unfortunatelly I was too mutch optimistic
I upgraded BMC ROM up to 3.20 but the server still had that trouble so I understood that sometime it runned fans at 14000rpm and other times at 10.000 rpms because of the room temperature: When I opened the windows the fans slowed down to 10.000 and at room temperature increased at about 24.5-25 °C they started go fast again!!!
So I tried disconnecting the inlet temperature sensor connector and it worked on the starting rpm point. Now I have the fans running regular at about 8000-10000 rpms depending on the CPUs temperatures. I guessed that they start incresing rpms at about 50-51 °C CPU temperature and I got those temperatures only testing the server with a CPU BURNING TEST after some hour but still work at those tenperatures with 8 CPUs at 100% working load for other 12 hours more. This is why I would like to slow down the fans speed, because I'm sure I won't have any kind of sovratemperature problems and more then this I will be able to stay in the same room of the server without becaming crazy for the loud.
I can't find anywhere the BIOS option (read somewhere in the net) that sets the mode operation of the FANs system. I hoped it was into the BCM LO100i BIOS (but it isn't there) or in a new System Bios (it doesn't exist). May be it is settable through ipmi-tools or hponcfg utility or others utilities that I can't install because they blame me for an unsupported hardware.
Hope to be able to upgrade to DL180 G5 system bios (it should be compatible and it is newer) may be I'll find the FAN option in the bios or may be that the utilities will recognize the hardware and I'll be able to set any options in other way... but I'm still stucked in this situation in these days