torrent WIFI download 4x slower than through cable

[m12345679]

Let me explain my problem:

 

I have laptop connected to fast TP-LINK router TL-WR841-n serving fast internet connection from my local provider.

 

When I connect to router through cable (ethernet) 

- Test on "speedtest.net" page shows I have 58.33Mbit/s download, 3.13Mbit/s upload

- Test in uTorrent (window after click: ctrl+G in uTorrent) shows acceptable scores:

Bandwidth results: Upload 3.5Mbit/s Download: 37.4Mbit/s

 

When I now connect to router through WIFI (laptop is just 20cm from router)

- Test on "speedtest.net" page shows still about 52.88Mbit/s donwload, 3.01Mbit/s upload (not perfect, but still ok)

- Test in uTorrent shows now much slower download

Bandwidth results: Upload 3.5Mbit/s Download: 8.0Mbit/s

 

I have uPnP enabled on router and see ports opened in both cases.

I have tried to turn off firewall both on router and laptop.

I have earlier used Cisco router and problem was the same.

 

Why is wireless torrent donwload speed 4x slower than through cable, despite opened ports and fast speed in "normal" internet speed test? 

 

Please help.