Engine wiring harness question

[Jean]

Since the E24/E28 cars came with both M20 and M30 engines I figured some of you would know this by heart.

I have an 91 m30b35 engine that needs a harness (the one that came with the engine is cut in multiple areas) and it will be installed in an E30 chassis.

How is the M20 engine harness (e or i) different from an M30 engine harness?

I heard the m20 harness would need to be extended in order to use it on an m30b35 engine (which makes sense since m30 is bigger), so would it make sense to use an m30 harness?

Does the M30 harness have more wires on it compared to M20 harness?

Thanks!

[James Crivellone]

Run the M20 Harness and extend a few wires (don't recall the exact ones, but its not many)

You want an I harness though, and depending on the chassis you are install it into you may want an 88 325i harness that does NOT have the new plastic fuel rail connections., late 88 - 91 are different I don't think they match up to the m30 fuel rail (i'd confirm this, not 100% sure, but I know the engine is longer so...)

[Jean]

James,

Is the m30b35 harness motronic 1.2/1.3 and b34 1.1? The chassis this would go into is not even Motronic anything as it's an 84 m10 car.

Thoughts?

Thanks!

[euroshark]

Not a big deal at all since the interface with the fusebox and the C104 in the glovebox are the only areas where the Motronic mixes with the car, and pretty much all that happens at that junctions are power distribution to the ECU and starter, and some signals for gauges. It's pretty darn simple overall.

[James Crivellone]

James,

Is the m30b35 harness motronic 1.2/1.3 and b34 1.1? The chassis this would go into is not even Motronic anything as it's an 84 m10 car.

Thoughts?

Thanks!

In that case use the M30B35 harness as you already need to hack the connector off to integrate it into the 84.

[Jean]

That's what I wanted to hear :) I think everybody was recommending m20 harness IF the swap was going into an a 325i car, and otherwise I wasn't sure why I would want to use an M20 harness over an M30b35 harness.

[BenM]

B34 = Motronic 1.0A (same as '84-'87 ETA)
B35 = Motronic 1.1/1.3 (same as the '87-'91 M20B25)


What James suggested is correct. The '87-'91 325i Harness should plug right into the fusebox (C101) on your '84, although I can't confirm.

If you were swapping in an M30B34 and using the earlier Motronic 1.0, you'd want to go with the '82-'87 ETA harness, as that would provide the proper electronics for the B34.

I will be swapping a M30B35 Harness and Intake Manifold into the Schnitzer S5, just to try and getting it running smoother, as well as getting the small electrical issues solved.

BTW, I responded to your WTB post on mye28.

Ben

[Jean]

BenM, pm sent.

[BenM]

Didn't get it. Send it to me again.

Thanks,
Ben

[Jean]

What is your username on mye28?

[Jean]

Guys, thoughts on this "the Super ETA harness. It is the only E28 with Motronic 1.1/1.3, so you don't have to splice wires into the fusebox, it justs plugs right in. " ?

[Jean]

George made a good point, most m30 engine harnesses are from automatic cars... So, would it make sense to start with an e34 535i 5speed harness or the "eta" 5speed harness as it's "compatible" with the b35 and 179ecu and extend whatever wires need to be extended?

[BenM]

Guys, thoughts on this "the Super ETA harness. It is the only E28 with Motronic 1.1/1.3, so you don't have to splice wires into the fusebox, it justs plugs right in. " ?

Sorry if I confused you. You would only want the Super ETA harness if you were doing the B35 Conversion in an E28.


Here is what I would do, if I were doing the conversion on your car:

- Find a complete '88-'91 325 Harness. Super ETA or "I", it doesn't matter
- Lay them side by side & figure out which connections need to be lengthened to fit the B35 (remember the M20 connections are in different places)
- Read the ETK's on what to wire into the fusebox. Maybe cut off the old 318i plug and adapt it into the 325 Harness?


There is a lot of info on this forum & mye28, you just need to find it.

Ben

[JoeMadoo]

I would recommend the e34 1.3 harness because
1. there is no extending at all, not even to the glove box area if you turn around the computer
2. it's more aesthetically pleasing.
3. Either way your going to have to change your c101 connection since yours is square right?

[Jean]

JoeMadoo - thanks, I've been reading your m30 thread(s) and taking notes. Sounds like I have a shit load more work ahead of me than I planned for haha.