Any way i can get a stable 50 in gta v?

[jldk6]

Right so here are my specs

GPU - GTX 660(The gpu in the recommended specs)
CPU - AMD FX 4100 3.6 GHZ(Piece of crap this is why im lagging)
RAM - 8GB(Dont know the make)
MB - 78LMT-USB3 GIGABYTE

So as you can see the obvious culprit is the cpu. Its like this in all games when inside a small space its fine but as soon as im in a place where there are lots of things on screen the fps goes from 60 to 20. All i want is a stable 50-45 so can is there anyone who can help?

 

[jldk6]

Btw im pretty my game looks worse than console at this point