the niki (aka650) turbo conversion is a fairly popular mod, taking the 2cylinder 650cc engine and adding a turbo does improve things, but it only gives less than exciting performance. i guess you're planning to do the same as that but using the 4 cylinder 850cc engine instead, hopefully making it a lot quicker than the 650cc turbo. that is something i've never heard of before, but i'm confident it will be a lot quicker, assuming you can fit the 850block in the niki. its a very small engine bay so i wouldnt assume it can be done.