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Hi guys, im currently collecting parts to do a h22a7 conversion on my b20a3 prelude. the h22a7 is out of a uk accord type r, I already have a chipped p28 ecu, a obd2 to obd1 harness adapter and a obd1 dizzy. Getting the engine into the car is no problem as I have mechanical and fabrication experience, however wiring is another story. My car currently has only got a “at control unit” part number “28100-pk4-712” which to my understanding is the control unit for the automatic transmission, I’m looking for any information as to how I would connect the p28 obd1 ecu to work with my gauge cluster for the rpm and speedometer and ignition barrel for power to the ecu. Is this something that someone has done before? Any information would be helpful
 

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Hi guys, im currently collecting parts to do a h22a7 conversion on my b20a3 prelude. the h22a7 is out of a uk accord type r, I already have a chipped p28 ecu, a obd2 to obd1 harness adapter and a obd1 dizzy. Getting the engine into the car is no problem as I have mechanical and fabrication experience, however wiring is another story. My car currently has only got a “at control unit” part number “28100-pk4-712” which to my understanding is the control unit for the automatic transmission, I’m looking for any information as to how I would connect the p28 obd1 ecu to work with my gauge cluster for the rpm and speedometer and ignition barrel for power to the ecu. Is this something that someone has done before? Any information would be helpful
You have to build a custom harness and wire up all the bare essentials for your setup.
You are missing a bunch of stuff just to get it running.

1. Fuel return line
2. Si fuel tank with baffeling or else your engine will die on hard cornering
3. Need to add a fuel mail relay into the harness for cutting off the flow of fuel in case of an accident so the fuel does not keep pumping.
4. VSS wiring to communicate the VSS signal to the ECU for vtec and also speedometer reading

Those are off the top of my head for now, but there is 2 others who did the B20a3 to H22 swap on the forum.
Pictures are dead in one thread but I believe the other thread its still there.

Here are the two threads I speak off:
1. 3rd Gen_ - 88S to JDM H22A build thread.
2. 90S model carb to H22 swap

By the way, do not waste money on an OBD2 to OBD1 adapter, you will need to be OBD1 converted to run the motor efficiently, and going OBD2 is a waste because the car does not need all that extra stuff that it never came with.

I sell the WireWorx harnesses and traction bar and swap kit for this swap, but if you want to build your own, then you will have to scour the forum for the threads that some guys gave input to making their own conversions work, mounts wise there is no info on that, and traction bars wise none either.
 

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Discussion Starter #3
thanks for the reply, I knew about the fuel return, I will be making all new fuel lines, I have the fuel pump and sender unit from the donor car so I’m sure I’ll be able to come up with something. I will be making a custom fuel pump relay and wiring as I know one of the pins on the obd1 ecu is for engaging the relay for the fuel pump, and if I can’t get that to work I will put a fuel pump switch somewhere. Are you saying that if I convert the dizzy to obd1 and use a obd2 to obd1 converter it won’t work? Would I need a full obd1 engine loom? Also would you say getting the dashboard wiring loom from an obd1 prelude would work with a p28 ecu so that I don’t have to wire the ignition and gauge cluster my self?
 

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Discussion Starter #4
You have to build a custom harness and wire up all the bare essentials for your setup.
You are missing a bunch of stuff just to get it running.

1. Fuel return line
2. Si fuel tank with baffeling
You have to build a custom harness and wire up all the bare essentials for your setup.
You are missing a bunch of stuff just to get it running.

1. Fuel return line
2. Si fuel tank with baffeling or else your engine will die on hard cornering
3. Need to add a fuel mail relay into the harness for cutting off the flow of fuel in case of an accident so the fuel does not keep pumping.
4. VSS wiring to communicate the VSS signal to the ECU for vtec and also speedometer reading

Those are off the top of my head for now, but there is 2 others who did the B20a3 to H22 swap on the forum.
Pictures are dead in one thread but I believe the other thread its still there.

Here are the two threads I speak off:
1. 3rd Gen_ - 88S to JDM H22A build thread.
2. 90S model carb to H22 swap

By the way, do not waste money on an OBD2 to OBD1 adapter, you will need to be OBD1 converted to run the motor efficiently, and going OBD2 is a waste because the car does not need all that extra stuff that it never came with.

I sell the WireWorx harnesses and traction bar and swap kit for this swap, but if you want to build your own, then you will have to scour the forum for the threads that some guys gave input to making their own conversions work, mounts wise there is no info on that, and traction bars wise none either.
I just read the posts you shared with me, thanks for that again. Looks like I’m gonna need the full loom from an si to make this work. Again thanks for the information it’s cleared a lot of things up😊
 
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