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Discussion Starter #1
Per the title, I am swapping out a V6 engine for a 1.8T engine on a manual trans B5.5. I searched for a V6 to 1.8L swap thread and didn't find anything, just some possible W8-to-other-engines threads. Here are the changes I've encountered and taken care of so far...

1. Had to change the power steering pump and lines. I did this as a unit, including the pump, cooler loop and fluid reservoir.

2. Changed the radiator support frame so that I now have the charge pipe/snub mount bar on there.

3. Will need to place the 1.8L airbox and proper SAIP air lines.

4. Changed the coolant hoses for the heater core supply and return.

5. Mounted the correct engine mounts on the engine.

6. Mounted the SMIC bracket and SMIC onto the car frame.

7. Will need to jury-rig the fuel supply and return lines, to accommodate the 1.8 fuel rail. The 1.8 has longer hard lines that hug the cowl before you get to the flexible hoses.

8. Will swap complete exhaust system with hangers, cat and O2 sensors.

Question: On the underside of the left frame stub, the V6 car has a Fan Unit Control Module while the 1.8T car, in that same place, just has 3 wires connected to a metal plate. What are these wires on the 1.8T for? Do I need to move that wiring harness from the 1.8 donor car?

Have I missed anything? The 1.8 engine will come in with the intake and exhaust manifolds, all the accessories and emissions and turbo plumbing in place.

I am also planning to get a 1.8T Manual ECU and wiring harness (my donor car had an automatic, so I can't use its.) and know that the ECU will have to be programmed to the car.

If you have experience with this swap or can just visualize the differences and can anticipate any issues, I'd like to hear from you.
 

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Member PZ is your source for all of this information. He is on short hiatus right now though.
Maybe some other veterans can chime in.
 

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Still recovering from vacation, but I am back.

I did the V6 to 1.8T swap on my 4Mo wagon when I also did a 6sp manual swap. You will need to swap the lower bumper wiring harness which connects to the V6 fan control module or your electric fan will not work. The ECU and engine harness are not plug and play, you will need to swap a couple of pins. I expect you can do this by matching the plugs but having a Bentley manual helps. Since I did a manual conversion at the same time, I swapped the entire dash harness from the donor as I had to pull the dash to replace the heater core too. The front springs will need to be changed for the weight difference. I have a writeup but the pics died.
 

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Discussion Starter #4
So as I suspected, I have to pull the metal plate and wires off the 1.8 donor car and place them where that fan control module was on the old V6 car.

Thanks also for that info on the springs.

Regarding the ECU and harness, I assume your comment on the engine harness/ECU compatibility is moot if I plan to get them both from another 1.8 manual Passat?

Thanks PZ.
 

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The 4-5 harness plugs under the ECU to the dash harness is the issue. The pins can be moved to match the 1.8T engine harness, but I don't know which ones to move since I also swapped the dash harness. Before I swapped the dash harness, the ECU did not power up. I still have not swapped the fan control harness, so I have not had the electric fan work the last few years. I had planned to do it, but did not have time to pull the car apart as I needed to drive it. Now I will do it before I sell the car along with wiring up the sunroof as the donor car did not have one and the fusebox is not wired for one.
 

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Discussion Starter #6
Okay, I get it now. I will look at all of the plugs to make sure they match up. Will it be pretty obvious, or do I need to be very meticulous and look at the numbers stamped by each pin on each plug and/or match all the exact wire colors?
 

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It should be easy to see, just compare each plug on the engine side between the 2 harnesses. Then re-pin the 1.8T harness to match.
 

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Discussion Starter #8
Will do. I just pulled a harness and ECU at the junkyard today. Might be a while, but I will post when I find the pin differences.
 

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Discussion Starter #10
No. Once I found out there were a couple of wires I had to pull the dashboard to get to, that car/project went to the junkyard. It was a sad day when I realized that. Unfortunate, since I had put in a lot of work already.

I recall I had started to look at the connectors under the ECU and did see some differences. It is really a matter of comparing the wire colors and positions in each connector.
 
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