[rotarymike]

Before I get into specific replies, let me summarize a little better what I'm actually doing.

I have an S4ish turbo drivetrain in an 88 vert chassis. Running and sorted out, more or less.

The car sat for 3 years of grad school. When I started messing with it again, I noticed it had basically rusted in half along the rockers and other areas - as in, no trunk floor or footwell left.

So I picked up a 90 vert in great physical shape but a tired engine. Has the bonus of new paint, new top, new leather, and being all one color, unlike my 88. I'm in the process of swapping the drivetrain in the S4 to the S5 so I can get rid of the S4 chassis. Already swapped rear subframe and suspension, starting to work on dropping the front subframe with engine/trans/suspension. Since I have the winter to play with it, I thought I'd do the drop-in properly (well, as properly as I can afford) instead of a hack. I'm tired of hacks, in general, although I see their usefulness.

On to replies and further queries.

Originally Posted by RETed

Electrical OMP:
Keep the S5 harness already installed.
Plug the E-OMP into the harness just to fool the stock ECU.
The S4 mechanical OMP is just going to operate normally, since it has nothing to do with the stock ECU.
No need to mess with a messy front oil cover swap.

I would like to change the front cover mostly because at one point, I had blocked the oil galley to the OMP, and tapped into the boss on the front to feed 2-stroke to the OMP. Even with all the return holes capped/plugged, the tolerance between the OMP shaft and the housing is great enough that the 2stroke leaks down over a day or so into the oil pan. If I try this again, I'll machine the OMP, I think.
Otherwise, simplify, simplify. When I pull the engine out of the S4, it's easy enough to pop it on the stand and do the swap. I'll be draining the oil and coolant anyway (sat for 3 years) and taking off most of the ancillaries for the harness swap.

Boost sensor:
You just need to repin the plug, since the only difference between S4 versus S4 boost sensor is a +12VDC reference.
The other three wires are +5VDC, signal (back to stock ECU), and ground.

Fuel injectors:
You can run the low-impedence fuel injectors just by swapping plugs - easy to find EV1 / Bosch type and installing resistors on each channel.

Is the S5 like the S4, in that the boost sensor is a different range for the NA and T2? Also, I may have a proper S5 boost sensor (N370?) in my spares bin.

For the injectors, I thought it would be a good time to put in some cleaned injectors, since I had to take the UIM off to swap the engine harness anyway.

Alternator:
Only difference here is I think the lug on the main power wire to battery?

The 2-wire plug is a totally different shape. Big oval instead of T-shape.

Main engine harness:
This is where is gets tricky, since it doesn't plug in with the dash crossover harness.
This is where you gotta repin or just brute splice the wires to make everything work.
This is basically just to get the instrument cluster working (i.e. oil pressure, boost) and wipers to work.

replacing the S4 harness with a decent S5 engine harness, so it should all plug in. I'm not worried about boost, I actually use a NA cluster and separate boost gauge. I remember getting the S4 turbo to work in the S4 convertible chassis took some rewiring - the 'vert chassis was an Auto so some wires were absent or in other places. I think I had to rewire the alternator completely (sense wires, not power wire). But the S5 harness I'm trading for is completely stock and looks mostly good.

As for the turbo, the S5 has a longer "adapter" pipe on the front from the oil pipe drain from turbo to the front oil cover.
Else, the positioning is identical, although it looks physically different - due to the turbo clocking.

So I need an S5 lower oil return pipe to use the S5 front cover. I can't remember off the top of my head what pipes I had laying around when I put the S5 turbo on, but everything fit more or less without too much 'splaining.
If necessary, I can make that from scratch if I have to.

Thanks Ted!