02 sensor help

[vago760]

I have a 89crxsi with a b16a od1 swap and im wondering if anyone knew exactly how many o2 senors are there suppose to be and the location of them? Not sure if there one or two

 

[crxhfz6]

one, on the back of the downpipe

 

[vago760]

Alright cool thanks.. But there is no 2nd O2 sensor?

 

[crxhfz6]

obd1 only has 1