Why WinSCP upload speed much lower than Ftp over TLS upload?

When I upload stuff to a remote server over WinSCP then the upload speed is MUCH lower (~2,8 KB per sec) than the upload over Ftp over TLS (~14 KB per sec) ?

Why ?`

How can I increase upload speed in WinSCP ?

What version of WinSCP are you using?

v4.0.4

OK, what protocol are you using then? SFTP or FTP?