Rsync adds a lot of overhead- The fastest way I've found to transfer a file is actually the venerable netcat.

On the receiving side, we open a socket, and direct it into a file-

nc -p 5678 -l > file.name

then, on the sending side, run

nc 192.168.47.1 5678 < file.name

That avoids the key exchange, the overhead of compression, the CPU to check for diffs, etc. Just pure copy.

I'd be curious the difference in speed you get.