I greatly increased the speed of yaourt by replacing curl with wget. I have no doubt that curl can accomplish this task no worse than wget, but wget is my favorite tool that I can use efficiently.
In yaourtrc, there is no mention of XferCommand, because yaourt uses makepkg for this. Therefore, make the following changes to the /etc/makepkg.conf configuration:
DLAGENTS = ('ftp :: / usr / bin / wget -c --passive-ftp -t 3 -waitretry = 3 -O% o% u'
'http: / usr / bin / wget -c -t 3 -waitretry = 3 -O% o% u'
'https :: / usr / bin / wget -c -t 3 - waitaitry = 3 --no-check-certificate -O% o% u'
'rsync :: / usr / bin / rsync -z% u% o'
'scp :: / usr / bin / scp -C% u% o')
## DLAGENTS = ('ftp :: / usr / bin / curl -fC - -ftp-pasv --retry 3 --retry-delay 3 -o% o% u'
## 'http :: / usr / bin / curl -fLC - --retry 3 --retry-delay 3 -o% o% u'
## 'https :: / usr / bin / curl -fLC - --retry 3 --retry-delay 3 -o% o% u'
## 'rsync :: / usr / bin / rsync --no-motd -z% u% o'
## 'scp :: / usr / bin / scp -C% u% o')