Can someone explain the difference...

Between OBD1 and OBD2? Im tired of hearing people talk about it and not being able to put in any of my own input.

obd1 ecu's are in 95 and older civics, while obd2's are in 96+, if i remember correctly.

>92 = OBD 0
92-95 = OBD I
96-98 = OBD II
99+ = OBD IIb

On Board Diagnostics montiors the engines emissions output, OBD 0 being the least amount of monitoring and restriction, and OBD IIb being the most.

So then for my swap, b16a1 into a 1990 crx, I dont have to change it?

Right, but you may have some other wiring to do, what model CRX is it?

Its a 1990 HF.

Ok good, the HF and the Si are Multi Point Fuel Injection, which means you don't have to do the conversion that a DX owner would, but yo're going to need to get the hubs off a teg or Si civic/rex, since the HF use's a smaller axles and hub, and the B series axles won't fit in them.

So I can still use the b series axles that come with the motor for the swap?

You can use them if you change the hub, there's no way around changing the hubs. You have to. The HF axles won't work in the B series tranny and halfshaft, and the B series won't work on th HF hubs

what about knuckles.

The whole thing, the HF knuckle is not compatible with the teg hub. You can however get the whole front suspension off a DX, Si, EX, whatever, as long as it is the same gen as yours, and no a four speed DX or a HF.