N62 Z3 Part 3: Wiring & Steering Sadness

After a couple weeks of research, today I started work on some of the wiring

Here is the very beginning of the process. Honestly this part didn't take long, the long part was figuring out what goes where (though of course knock on wood, as it's not done yet). I tagged each wire with what pin it originally was installed on, as well as where it needed to go (or indicated if it was removed, or added when not previously there at all). That way everything is fully reversible in the future, or traceable if something was wired incorrectly. It also means if things were done correctly that it is very easily reproducible in the future

Ah yes, electric noodles

To label them, I printed some nice little small tags at home to document the wiring changes and taped them onto their respective wires. Though you will see later as time goes on and I get into some wiring I didn't initially plan for, that my tags become handwritten and a lot bulkier. Oh well

At this stage most of the wires on the DME connectors have been moved to the correct spots, added or removed as required. It was around this point I realized I was missing an IVM harness - no big deal, I cut all the harnesses off my X5 parts car. When I found the box of harnesses - not only did I find the harness but I also found an IVM. And a Valvetronic DME! I had just ordered these parts on eBay the night before, thinking I left them in the X5 when I scrapped it, so I was really happy to have found them. I didn't pay much for the ones I bought so it won't be bad to have spares. But that meant I could still move forward with the swap in the meantime!

You can see the IVM and Valvetronic DME both installed in place in the below image, just barely though (the IVM has the green harnesses, the Valvetronic DME is the one with the red/brown wires going to it, on the other side of the tan lid from the IVM)

However, not everything today was positive. I realized that the IVM harness I was missing went on the bottom of the IVM... I honestly hadn't given the IVM much thought up until this point. I thought it was self-contained like the Valvetronic DME (woah, is that self-contained?). I didn't even know there were harnesses on the bottom! Oh how naive I was...


So, there are 4 total harnesses on the bottom of the IVM and 3 of which were completely unaccounted for, the other was the one that I was looking for earlier. The three harnesses I had no idea about seem to be pretty simple though - they are a 1 and 2-pin connector with large red wires coming off them and another with a large brown wire. So I also want to mention again how naive I was because like I said I had been researching this for weeks and only given the IVM any critical thought the night before... luckily, I had enough foresight to print out the IVM pinout to at least help me figure out some of this wiring

So the prinout on the IVM I had confirmed that the brown single wire one on the bottom is a ground. That's simple enough. The red ones both indicate voltage terminals, so I think it is just a matter of tracing them and seeing where they go - most likely, they just go to fuses and I will match the fuse size to whatever the stock fuse size was. That leaves just the harness I was originally looking for... which had the most wires by far. I labelled them as you can see below and installed the 3 wires that I knew where they went. I've done a bit of research since being home and believe I know where the rest of these wires go - so I think I can finish wiring the IVM in tomorrow

Also a big thanks to Randy, for answering my questions about CANBUS systems! There were four CANBUS lines on that IVM which seems really weird - usually you only see two CAN lines running into modules/DMEs, but I think it's been figured out


Before leaving for the day to go home and research IVM wiring stuff, I hacked the cats off the headers and test fit them

IMO those "Torch" sawzall blades suck

It is a very tight fit. The stock steering shaft runs right into the O2 sensor so at the bare minimum the O2 sensor will need to be rotated. I also want to try with the engine lifted a little bit more into its proper position - it had sagged a bit (nothing is fully bolted yet, just supported by a trans jack from below) overnight. I'm going to lift the engine and remove the O2 sensor and try again tomorrow. The passenger side fit fine so just a matter of steering shaft fitment and then of course it will need custom exhaust work. I actually installed these headers in place, even with the engine mount in place, though I removed the engine mount later to try to get the steering shaft in place. So overall clearance isn't that bad... just need to get the shaft hooked up!


I got a ton of good feedback about Part 2 of my build thread about how that post ended in a discussion about alternators. Alternators are a solid closer for any build thread post. So lets try to re-create that magic again


I did not remove the engine today to test fit the alternator, I had some other shop work to do, but when getting home researching N62 electrical harnesses I noticed - out of the corner of my eye - this diagram for the N62 engine alternators

Am I crazy or is #2 an alternator that is a little bit smaller in size than the stock unit, #1 in the diagram above? It may use a different alternator bracket (it also seems to have an extra bolt location on the top middle?) so I will be digging into some RealOEM diagrams of various N62 powered cars shortly to see if I can find this alternator... where is it? What is it from? Will it fit my engine and will it charge my battery adequately? Will it mean not having to notch my framerail?

So many questions. So many RealOEM diagrams. The build continues here in Part 4

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