First off, OBD0 stuff. TurboEdit (now Open TurboEdit) has come a long way, supports a lot more than it did years ago, and is still free. This is the cheapest route to go for most CRXers, since it's OBD0 based and the chipping required is minimal.
The ECUs you want to have for OBD0 stuff are:
PG7 (88-89 Integra D16A1)
PM6 (EF Civic/CRX Si D16A6)
PM7 (89-91 Civic Si ZC)
PR5 (90-91 Integra ZXi)
PS9 (EF Civic EX, usually AT)
PK2 (88-91 Prelude B20A)
PM8 (CRX HF, D15B6)
PR4 (90-91 Integra B18A, there are OBD1 PR4 as well)
There are some others, but those are the ones you're likely to encounter.
Chipping OBD0 is pretty simple, it requires at the minimum a chip, but preferably a socket and a ZIF socket to allow for more switching the chip, as well as a header for datalogging. I usually get all my chipping parts from Moates. I'll use the PM6 as an example, because it's very common, especially for CRX owners.
The year of the ECU is usually stamped in ink on the side, to the left of the label. Here are three PM6 ECUs, two with stamps:
The picture is kind of crappy, but you can see the middle one has no ink on it. The boxes outline the label and model of the ECU, the middle three numbers on all of these say "PM6". Generally, you want a "PM6-A09" for chipping. As far as I know, all 1988 PM6 are not easily chippable. Yes, it can be done, but IMO it's not worth it, considering how easy and cheap they are to get. Some 1989 ECUs are chippable and some aren't, you can look for the "A09" stamp, but to be sure, you have to pop it open.
Here are two PM6s. This one is non-chippable, the one labeled '89 from the picture above:
This one is chippable, the un-stamped PM6-A09 in the pic. The boxes outline the external EPROM (which you replace with a chip) and the place to add the datalogging header (CN2).
Chipping a PM6 is pretty simple. You just remove the EPROM and add in a socket and ZIF socket. Depending on the socket and ZIF socket you use, you may need to slightly bend some components for clearance, but there is generally plenty of room. Optionally, you can install the datalogging header to CN2.
Here's a chipped PM6, using a low-profile ZIF from Moates:
That's about it for chipping OBD0 stuff, though there are variations. The ideal ECU to get IMHO if you're staying with OBD0 is the PS9 AT, since you can use the automatic's lockup solenoid output for VTEC, it can pretty much do anything. This may be the same for auto PR4s, I haven't done it.
Now on to OBD1. OBD1 ECUs have a LOT more aftermarket support, from free programs like Crome Free and ECU control to mid-range things like Crome Pro, and up to Hondata and Neptune. The most common OBD1 ECUs you'll see are:
P28 (92-95 Civic EX/Si Del Sol Si D16Z6)
P06 (92-95 Civic Dx D15B7)
P30 (Del Sol VTEC OBD1 B16A2)
P61 (DA Integra GSR 92-93 B17A)
P72 (DC Integra GSR B18C1 OBD1)
There are, of course, MANY others. Generally the most desirable OBD1 ECUs are P28s and P72s. They both can run any engine, but the P72 has the advantage of supporting knock sensors and IABs (which are used in the B18C1 and H22). Other non-VTEC OBD1 ECUs can be chipped and modified to support VTEC and enable/disable automatic transmission.
All OBD1 ECUs are chippable, so you don't have to worry about looking for a date stamp. They have the same kinds of labels on the sides that the OBD0 ECUs have, again with the middle three characters giving the model (ie, "-P28-").
There is more involved in chipping an OBD1 ECU than an OBD0 ECU. In addition to adding a socket and chip, and additional chip must be added, as well as two capacitors, a resistor, and a jumper. For datalogging, the header must be added to CN2 and a jumper must be cut. Moates conveniently sells kits with the parts needed to chip an OBD1 ECU, as well as a USB serial converter for easy datalogging.
This picture is a chipped P28. The boxes highlight the areas where components need to be added (on the right), the datalogging header (lowest on the right), and the jumper J12 that needs to be cut in order to datalog.
This is a P72, also chipped. Notice the extra board taking up the upper-right quarter of the ECU, this is the knock board.
*note this case has been modded, it normally looks just like a P28 when closed (other than the label)
Conveniently, OBD1 boards have a dotted outline around the EPROM area, and you just have to add components to all the blank spots. The smaller ones are labeled with Js, Rs, and Cs for jumper, resistor, and capacitor, so once you have the parts it's pretty simple.
Finally, OBD2a stuff. This crap is useless, but here's a pic of a P2P (D16Y8) ECU opened up:
For any of the chipping stuff, all you do is desolder the board, either removing components like with OBD0 boards, or opening the blank holes with the OBD0 CN2 or any of the OBD1 stuff. I find the easiest way to do it is use a desoldering braid and wick it all off, then remove the component, or install the new one.
If anyone wants me to add more, I will, and eventually put it up as a how-to or something. I'll add it to the FAQ for now. Any specific questions?
