Sergio Ruiz

So I have a h23a engine I pulled from a 92 si that I bought. I got a f20b swap I just bought that came with ECU and wiring harness. I have the original wiring harness for the 92 prelude and the intake manifold also. My question is what do I swap over to make it work. I heard I can use the harness the engine came with but how do I do that? Has anyone ever done this swap before? Reason is I have my map sensor and evap purge valve on firewall and other sensors that are not located on the engine but have separate wiring harness going into dash to the ecu.

TimiK

1) use F20B ecu with its wiring harness
2) use original harness, change sensors, dizzy, oil pump (and intake manifold?) etc to usdm and use chipped ecu (with tune)

Sergio Ruiz

So just pull out the original wire harness from firewall insert the one that came with engine and just hook up the ECU straight up to it? That simple? Nothing else needed to be done to work?

Accordian47

Keep an "uphill" approach with a glad attitude and you'll be swinging not only those thoughts and concerns but components in no time. From start to finish your looking at basically just using that f20b ecu, keeping her "down" near the floor area, pulling the original engine harness out of the car, right on out through the firewall side (pulled from the engine bay), putting the f20b harness on the f20b motor by connecting all the harnesses, lowering it in and then snaking the harness down into the passenger's footwell area, plug it in and you should be good to go. If it's going into a '92 Si then your ideally going to want to have a matching OBD1 engine, ecu and harness but the F20B is a OBD2 motor, SO...Run the F20B motor, ecu and harness in a OBD2 configuration by adding either an 02 sensor to your exhaust or running a no fouler/02 sensor simulator, another option is switching to an OBD1 Distributor and running the motor in a OBD1 configuration, using a ecu conversion harness along with a OBD1 ecu.

Sergio Ruiz

I would rather just add the o2 sensor and use the f20b harness and ECU. Great thanks. Any other pointers? I know I have to swap out the driver mount bracket from engine cuz it doesn't match up for the mount.

TimiK

Rebuild your swap engine while its out

Accordian47

Running the F20B in a OBD2 setup is the way to go, it is an OBD2 motor after all. You'll just need to have a secondary (post cat or "downstream", 02 sensor in place. You can either, drill a hole in your current exhaust and have a bung welded in or you could try and run a section of exhaust from an OBD2 car that will fit your car. One other thing to consider is that the '92 Si, being an OBD1 car, does not have a OBD2 scan port/connector under the dash. I'm not positive but I think the ECU looks for the connector in it's criteria for illuminating the check engine light, if not then your fine, worst case, you'll have to either wire one in or run a dash harness and connector port from an OBD2 car. Also, most states require the OBD2 scan port be present for connecting a scan tool to determine emissions status, though they may not car if the car is supposed to be OBD1, idk.

As far as the swap in general goes, here are my tips:

1. Torque as many of the fasteners as you can to spec
2. Rebuild the motor or replace as many parts as you can while its out, as TimiK stated. Its so much easier with the motor out and will really pay off in the long run and in terms of piece of mind while enjoying the car. I recommend buying parts online, using genuine Honda wherever possible and RockAuto.com for everything else.
   1. Headgasket (Use new head bolts)
   2. Waterpump
   3. Timing Belt
   4. Seals (Crank rear main, crank/oil pump front main, valve stem seals, balance shaft seals, distributor o-ring etc.)
   5. Piston rings and rod/main bearings (If you want to tear it down that much)
   6. Ignition System Tune Up: Plugs, Wires, Distributor Cap and Rotor
3. Label as much as possible, use painters tape and a marker. At least try and label all your engine harness connections
4. Plan ahead and do things in the right order.
5. Plan ahead for all fluids and make 1 trip to the parts store instead of 3
   1. Engine Oil and Filter
   2. Transmission Oil (Honda MTF for manual and Honda ATF for automatic)
   3. Coolant (Get the right amount and be sure to mix with water if the kind you buy isnt pre-mixed)
   4. Brake Fluid (For manual transmission only and only if you have a hydraulic clutch, unless your doing brake work too)
6. Use and engine hoist, rent or borrow one if you have to. I don't recommend installing the engine in through the bottom by raising the front of the car up, it should be dropped in from above as a complete, engine and transmission assembly.
7. Try your best to be patient with fasteners, if it turns too hard, back it off. Avoid stripping threads and fasteners at all costs. Use the right bolt for the right application area (Transmission-to-Engine Mounting Bolts and Engine Mount Bolts can easily be confused, they are different lengths.
8. Clean as much of the components and car as possible while its apart.
9. Take your time with the project, ask questions and be resourceful. In the end it pays off, you will be that guy who did.

Sergio Ruiz

I have the original intake manifold with all the sensors and what's not and the original wiring harness with distributor for the 92 si. Would it just be easier to use that harness and swap the parts over to the f20b and just get a obd2 to obd1 harness adapter? Seems the car would work better knowing it has all it's original parts instead of leaving stuff off or missing. Will the ECU still work even if it's missing the downstream sensor or is that a for sure thing no matter what I need to add? Is there a link someone has for a complete swap for f20b into 4th gen prelude so I can see my options?

Accordian47

Sounds like a legitamate plan, you can definitely run the motor as obd1 as long as you swap everything over. As far as the ecu, you would need to run a obd1 ecu at least, it would need to be a Honda ecu that would run the obd2 f20b motor, so that might be a little tricky, some other ecus technically can run the motor without problems, such as a f22 or h series ecu but dont quote me. Most likely the solution is to run a chipped obd1 ecu, the modified obd1 ecu would ensure it could run the f20b without problems. The adapter harness is required so that the obd2 engine harness you have can plug into the chipped obd1 ecu, obd1 and obd2 ecus use different plugs.

Sergio Ruiz

Ohh k makes sense. Ok well I will have to get a different ECU then if I'm going that route. I will have to sell the one it came with. which ECU would work best without breaking the bank?

TimiK

Contact your local tuner and ask what he uses to make a proper map for you - that do you need hondata or is chipped ecu alone enough

Sergio Ruiz

I saw some chipped ECU p13 for 150 on ebay. They tune it exactly according to the engine being swapped into the car you putting it in. Sounds about right?

TimiK

Basemap is not a tune, its just to get your car started

Accordian47

He would only need a basemap. He needs a chipped oem Honda ecu like a P13 that has a basemap set to run an f20b. Hes not boosting the car or anything.

TimiK

basemap doesnt run flawlessly

Accordian47

The chipped p13 he is referring to is one that is offered by a company that will install any "basemap" tune on it you want. He only needs a P13 that will run a STOCK F20B. Its not as much a "basemap" as it is a P13 with a oem Honda F20B tune on it. So as long as the tune burned onto the chip is one of exactly the same as a oem Honda F20B ecu then thats all he needs

TimiK

I know and I dont trust in any basemap