ive honestly been thinking about welding the centre as the price of LSD's are crazy.

my question is this, would it be 'necessary' to have a lsd/locked diff in a 240k with a rb25det? or will an open diff suffice?

Depends on what you want to use the car for. If its just a regular street driven car and you don't plan on flooring it off the lights at every occasion then the open diff is fine. Welded diff is illegal for street driven cars over here.

I would not use a welded diff on the street, as it is noisy at low speed and would be scary in the rain.

If you have gone to all the trouble to build a car with an RB etc. I would think that the cost of a LSD would be nothing compared with what you have spent to get to this point.

Get a nice LSD and enjoy the handling benefits.

Ron

The OBX helical LSD is only $375. It's a Chinese Quaife copy and the guys at hybridz.org have had good luck with them. They did have a lot of assembly mistakes on the early units, so the buyers were forced to take them apart and check to be sure they were put together right. Some had the gearset backwards. I'm not sure if that is still a concern or not.