SR20 Oil Filter Housing Mystery Bolt, What Is It?

[s13q]

So I was under my car this morning looking to see if a T-piece would fit in place of the factory Oil Pressure sender when I saw this bolt.

Judging by the way it sits it looks like its a direct feed into the oil line. I did a lot of research to find a diagram or something but nothing came up.

Anyone know what it is? If it is a direct line into the oil what size is the bolt?

Thanks!

The bolt can be seen in these pics, top left above where the oil pressure unit goes.

http://i272.photobucket.com/albums/jj194/sr20det_motor_build/filterblock1.jpg

http://img441.imageshack.us/img441/9554/170920106201small.jpg

[nickauger]

If you're talking about the big bolt in your picture, its the oil pressure relief valve.