N62 Z3 Part 5: DME Boxes & More Wiring

I wanted to make sure all the wiring I am doing is reversible in the future - so instead of cutting and splicing anything, I want to acquire harnesses and whatever else is needed to tap into existing connections in a reversible way. So we begin with a junkyard run. I needed a few specific things - some of the power plug adapters, a crankshaft sensor (I don't know why the seller removed it from the transmission in the first place) and about four of these other various harness connectors keyed a specific way. I couldn't find those keyed harnesses, I think those are E36 era only and they didn't have anything that old at this yard but I did find the power adapters, crankshaft sensor and a bunch of spare DME's. And an IVM

Got to the shop and installed the crankshaft sensor

And then shortly after, the buyer for the M52TU finally showed up... in a Prius! Who needs a pickup truck when you've got a Prius? I was not expecting it to fit, but sure enough...

With transmission and intake manifold on it too! Crazy


My shift linkage also showed up the day before so next thing I did was work on removing the automatic shifter components

Then I went to test fit the linkage... it was too long. Also, and more importantly, it didn't even fit the transmission. Sooo, seems I will be sourcing an OE E60 shifter carrier. They aren't super expensive new - about $60. I think I will just modify an existing selector rod to fit. Everything did seem okay clearance-wise though. May need to trim a little foam out like I originally planned on doing but that is not a big deal. The selector rods for these transmissions have kinks around the giubo area, which implies to me it's a pretty tight fit even on the factory cars with these transmissions. What I'm getting at here is the height seemed like it would be okay

But this specific shifter carrier just didn't fit the transmission at all

Oh well. That seemed like a bit of a stretch anyways...


With the M52TU finally sold my engine crane was free and after checking the transmission shifter linkage I was ready to get the engine out. So, out the engine came

The Dunklenator!!! Although, it won't be Dunkel Green for very much longer...

And it's out! Such a huge engine

My wire also showed up for the PWM fan stuff. Pretty thick stuff! The positive will run from the 50amp fuse in the DME box to the fan, the ground will go to the nearest ground point - maybe where the engine grounds to the framerail

Also with the engine removed I can share where I had to do in the first round of clearancing. More clearancing is in order but it fit enough to get the transmission bolted in so that's a huge win in my book!

Time to sit back and admire the empty engine bay... haha

The supposedly uncut engine harness arrived the next day though I spent that morning helping my sister buy a Z3... she blew the motor on her Subaru and was looking for a replacement so of course I recommended a Z3 and of course she wanted one after test driving one of mine... it's a Topaz Blue 2001 2.5i 5 speed - I quite like these, even the smaller displacement I6's are a lot of fun in the Z3 chassis

Back at the shop, I started figuring out all the wiring routing once again. One of the main reasons for buying the IVM at the junkyard the other day was to get the wiring harnesses with it - I cut the leads much longer this time to give me more room to run them where I needed them to go without splicing, since I don't think I can find the pins for those lower power terminals. The top IVM is the one I had before, the bottom one with the much longer wires coming off it is what I have to work with now. I am still a little unsure the exact routing I will follow. I may drill a small hole in the DME box so these wires can come out the bottom and go straight to the IVM which will be mounted on the side of the DME box. With a rubber grommet and maybe some silicone sealant it will remain watertight. I am going to experiment with my parts car DME box first

Now to work on the engine harness...

The first issue I ran into was the E53 engine harness didn't plug correctly into the coolant temperature sensor on the water pump. This engine is from an E60 but the harness (and DME, as well as DME tune once that is done) is from an E53. I searched the part number for the E53 sensor I needed and it was shared with quite a lot of cars - in factI had another one of those sensors installed in a spare motor, so I removed it and swapped it on and it plugged right in

The next issue is a little more odd and relates to the camshaft position sensors. The RealOEM diagram for the E53 indicated four "female" plug type cam sensors. The RealOEM diagram for the E60 engine indicated the exhaust camshaft position sensors (CPS) were the female plug type and intake CPS were male plugs with leads


The engine configuration seems correct based on the E60 diagram, since its an E60 engine. However it is an E53 engine harness but for whatever reason, it doesn't seem to have leads off the harness to plug into four female plugs like the diagram indicated. Instead - the driver's side bank has one female and one male, which plug into the harness (even though they shouldn't, as the E53 harness should need four females)

But at least that side plugs in so... whatever, I guess? The driver's side on the other hand has one female and one male like the other side, but it for some reason doesn't plug into the harness (neither of the circled connectors are plugged in)

To get them all to plug in means the driver's side bank will have one female and one male CPS plug and the passenger side would have two females, which I find very odd. I will do some further investigating into this


Later that evening I decided I was getting held up a little too much at the electronics side of things. I will still not be cutting anything on the car side, but I am going to just splice whatever I need to splice to get it to where it's all wired up and I can attempt a test start... so the first step was to get the spare DME box out of my parts car and mock everything up to that. With the spare DME box out, I realized I had a second DME fan and with these extra computers in the DME box I thought some extra airflow might be a good idea. The stock fan blows air out the bottom of the DME box. With the addition of this fan, I may reverse that flow and make this upper one the exhaust - I think that may be better for airflow. I am also thinking I will hardwire this upper fan to a switched source so it be on any time the car is on

Anyways, None of that is even important now, I just got a little distracted earlier and airflow management has been something nagging at the back of my head so now I won't worry about it until/if it becomes an issue down the road


I then started mocking the fuses up, I also decided I won't be using the stock plastic DME holder piece either. It just makes things a little too tight

Figuring out where the power distribution block is going to go...

I am going to trim those last two or three sections off to shorten it, so I can fit it on the side of the DME box since the hole to mount it is currently hanging off the edge

I am also considering finding a similar distribution block with less fuses. I really only need the 100a, 50a fuse and a line to feed the 40a fuse, this line will go into one of the 80a fuse spots. I have left the rest in there as extras but I am starting to think I won't need them... and cutting three off still leaves me with one extra


My goal is to make it so everything is either being powered off the distribution block and "self-contained" to the DME box or spliced into a harness that will plug into the stock harnesses. Then I just drop the DME box into place, add the required body harnesses and it's good to go! I will power the distribution box with a battery cable from the positive terminal to the fused side of the 200a terminal


Another late night at the shop... my work bench is a mess!

Currently my continuous power source is from the chassis - the more I think about it though, the more I think I will end up routing it off the distribution block. So there's at least one other thing I will likely run off the distribution block!


Starting the process of getting things spliced in and everything in place, I am keeping everything "isolated" as much as I can, working on the bench and not disrupting any wires on the car at all until required

The stock DME box was replaced with my modified one, then the fuse panel was first to be installed in place since the wiring for that will sit underneath the wiring for everything else

...and then it got moved back out to finish the wiring for the IVM body harness (green connector at the top). This meant integrating it with the factory Z3 body harnesses so at this point it became attached to the car

And then once finished up everything came back out temporarily again in order to prepare for the next step which was routing the power wires for IVM through the DME box. Or so I thought. As it ends up, there is a metal panel under where I drilled the holes - so when I remove the DME box again I will drill a new hole(s) where needed. I know, I know... a picture of an empty box. Exciting

I went ahead and mocked up the IVM power routing even if I couldn't fish the lines through the DME box into their final position... it's pretty simple when it comes down to it really, at least as far as power supply. The body harness was the really complicated part. The power supply for the IVM is just the below image, plus a ground

In (very) rough position after checking wire length and routing with everything in place

And with that, all the major wiring at this point should just about be finished. If I was otherwise ready to test start the car I would only need to run two more lines between DME and IVM (I am waiting on those pins to get here first) and I still need to run the grounds - none of those are run yet, but that's simple enough to do


I stopped short of getting everything set in place because the DME box will be coming back out again for further modification after I buy more dremel bits. As such I did not want to install it all just to immediately reinstall it next time I worked on the car


Hopefully that just about wraps up the wiring, at least the bulk of it... Whenever the pins/harnesses get here and I have extra time I will make it a little nicer/neater and revert all spliced connections to single runs of wire with crimped pins on both ends, like factory. But for now it's really nice to have this off my plate. I will go back and double check all the wiring changes before I attempt a first start, but I did hook the battery up with everything connected and put the key in position 2 and there were no fires at all, so at least for now that's a win in my book


What's next? More wiring, of course. And fuel system stuff

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