im dont really know these code names for engines but for what car it the sr20det used (im guessing the silvia) and what are its specs?

Jeff240sx

It depends on the year engine.  They were in Japanese 240sx's, or Silvia's.  s13 is 205 hp, s14 is up to 220, and s15 is 250.
They also came in a few other cars, like the Australian 200sx, but for some reason, the hp was turned down... from what I hear, to around 180-ish.
-Jeff

and i can buy them here cause i dont think they sold 240sx's here with that engine btw thanks for answering my question

You can buy that one, or you can upgrade your current KA24DE to a turbo. It's easier to find parts for  the latter.

Jeff240sx

You can buy the sr20 motor from places in USA, but they ship them directly from Japan.  No car in america came with the sr20 engine in it.  Unless you buy a custom car with one.
-Jeff