turbo exhaust housing sizes
 

I got a 88 rx7 t2 with a streetport. im looking on doing some auto crossing this year and was looking into finding the right size turbo for for what i want. Ive heard that a .84 exhaust housing would be good for quick spool along with a small compressor housing. i got a friend that has a turbo with a t4 exhaust housing but its a .68 exhaust. i was wondering if this would even work for our motors. what is the smallest exhaust housing usable on ours motors. Im only looking on running about 15psi.