what settings did you use ?
just now I am using this config on my 660Ti with 3GB of RAM
-i 0 -C 2 -m 1 -l S56x8
This gives 172-174 kHash/s and with slight overclocking this can be raised to 186 kHash/s
this config requires 56*8*4MB = 1792 MB of available memory on the card.
Not sure why, but those setting crash my computer, I did try auto tune and its now using S56x4, giving a hash rate of 171.
Also the Hashrate drops If I use GPU tweak and select the gaming profile, which overclock the card.
From gpu boost default 1045 overclock 166
Mem Clock default 6008 overclock 6048
Power Target default 100 overclock 110
When reset to normal the hash rate jumps up to 170 from 145.