Swapping in OBD1 B18C1 into OBD1 DA. Several wiring questions within.

Okay, guys. The time has come for me to finally do a swap into my DA. I decided to go with a B18C1 (OBD1) as my swap of choice.

The questions I have are as follows…

Both the engine, and car are OBD1, so I’m assuming I won’t have to do any major modding to the engine wire harness, right?

I know I’ll need to do some wiring to wire up VTEC, which shouldn’t be a problem. However, I want to make this as close to a “plug and play” affair as possible, so I’d like to avoid cutting if

So, here’s the root of the question. If I do this swap (both the car and engine will be OBD1) will I need both of these kits, or just the one for VTEC wiring?

ECU Conversion Subharness

VTEC Subharness:

Both, or just the latter?

I will be doing the swap in a month or so, and I will be under VERY tight time constraints to get it in, so I need this to be as quick of an affair as possible. I’ve already got the mount/hyrdo-cable situation taken care of, now, I’m just focusing on the wiring aspect of it.


Actually, I do have a question regarding the Cable-to-Hydro conversion bracket. I was reading this article:

and it says towards the bottom

The original Ls cable transmission comes with a 17mm bolt that holds the tranny to the tbracket
unfortunetly the hydro transmission that comes on newer model cars comes with a 19mm bolt.
NAPA doesnt do this kind of work, and home depot doesnt carry a drill bit that will cut through it,
so you will have to find a local industrial machinery that will do this for you, mine was $40 dollars.

will this apply to me, too? do I have to do some kind of drilling for it to work? As much as I had researched that issue in the past, this is the first I’d ever heard of this. Anyone care to shed light on the situation?

Your main wiring issues will be as follows:

  1. You need a vtec subarness that consists of: vtec solenoid, vtec pressure switch and knock sensor plugs. Your factory obd1 plugs will work directly with an obd1 gsr ecu, but you will have to wire in those three pins for said sensors. Its easy, ff-squad has a write up on pinning ecu plugs. The subharness should come with instructions on which locations the pins need to be installed.
    edit You will also need to wire in the secondary butterfly valves in the GSR intake manifold, or bypass them all together. You should be able to have this made with your vtec subharness, and wire it in the exact same way you do the other pins.

How to de-pin an ECU plug:

Pins that you need to tap into for adding VTEC to a non-vtec ECU plug:

  1. You will need to extend the wires from the firewall-mounted MAP sensor to fit the throttle body-mounted MAP sensor.

As far as drilling/tapping the transmission, I’m not 100% sure… but its not a hard task. Finding a bit the right size, or a shop that can do it, should be fairly cheap.

You’ll also need the drivers side block-mount in order to bolt the motor to a factory DA engine mount…

Pull that off of your current DA motor (drivers-side of the motor, 3 bolts) and install it on the new motor. This way your stock DA mount will bolt on. The DC ('94+) mount is different
I’ll see if I can upload some pics to help explain in more detail.

So in summary… the VTEC subharness you linked to should solve 95% of your wiring issues. Just extend the MAP sensor wiring and you should be good. No “ECU conversion” harness is needed as your car is already OBD1, and you’re going to be using an OBD1 ecu, so it plugs right up. Then just use the stock DA block-mount, and it should be all downhill from there.

I dont really know about the Cable/Hydro conversion as I’ve never done it before. But the kits they sell should be pretty straight-forward.

IAB is for the butterflies, right?

So, the 2nd link posted (VTEC conversion harness) will take care of all that? If you enlarge the pic, it shows the following:
OBD1 or OBD2 ECU Pins
VTEC Oil Pressure Ground
VTEC Oil Pressure
Firewall quick disconnect.

so that harness will cover all the bases?

And if anyone else can provide information on the hydro to cable bracket, it would be greatly appreciated.

Also, if I won’t need the ECU Jumper Harness (first link I posted), why would they offer an “OBD1 to OBD1 Conversion”. What would that be needed for, or why would they even be selling it if it weren’t necessary?

Correct, that harness will take care of your wiring needs (except the MAP wiring extension)… and yes, butterfly valves = IAB.

And, that’s really the first I’ve heard about bolt holes being different thread pitches on a hydro trans vs cable trans… an easy way to tell would be to pull up a cable and hydro trans on oemacuraparts.com or acuraoemparts.com and see if they list different part numbers for those rear bolts. But as I said, that’s the first I’ve heard of them being different sizes.

any insight on the last question, regarding why they offer such a kit (OBD1-OBD1) if its unnecessary?

and maybe its because its late, and I’m tired, but the small write up you posted mentions de-pinning plugs. if all I’m doing is adding some wiring, why would I be removing any of the existing wires from their pins? Wouldn’t I just be putting new wires in unused pin locations? if not, where are the original wires going that get removed and swapped for these?

i’m very sleepy, and hope you understand that last question.

You’re correct in that you won’t be removing any wires from the factory harness, just adding them… I just said de-pin as that is the term that came to mind. But you will still have to open the plug/harness to insert the new pins.

That obd1-obd1 harness is for adding a VAFC/SAFC tuning unit, like the Apex-I vtec controller or any other ‘piggyback’ tuning unit. That way its all pre-wired and you don’t have to splice any wiring. With that harness, its all pre-wired for you. As long as you’re keeping the motor stock, a stock gsr ecu is all you need. Besides, those piggyback tuners suck. If you mod your motor and need tunes, pay someone who knows what they’re doing and get your stuff dynod and tuned the right way.

I didn’t notice any glaring errors in what Unified said (which is a shocker :stuck_out_tongue: ) but did want to be clear that you will be using your LS engine harness, correct?

yes, I will be using my LS harness. Would using the GS-R harness make things any easier?

Just use your LS harness and modify from there, that way you aren’t dealing with the headache of trying to modify the GS-R harness to the fit

You do not want to use the harness from the donor engine. It is (in all of my experiences) a much bigger pain in the ass. Stay your course, I just wanted to make sure you were using the one that originally came in your car.

Oh bite me lol.