e23 728 M88 swap

[mottati]

Next up was what i was really most nervous about, wiring. This is a pretty simple car. No OBC (note, this will cause me some issues later on), no check control, no ac, no abs. Just a 19 pin connector, that's barely half full. But still....

The M88 had it's wiring harness, dme etc. But that was a 17pin, and i wanted it have it plug into the e23 19 pin, so i de-pinned both and figured out where things went. The lack of obc and check control meant i still had some extra wires, but they're just in the connector, with nothing on the car body harness side.



But then i hear this drip, drip, drip, drip, and see a trickle of bmw blue coolant running from under the back of the engine...

My initial plan was to use the e23's M30 coolant pipe off the back of the head. But it is quite a bit shorter than the M88 part, due to the size difference of the head. I was not able to get the heater hose to seat properly, and after a few days sitting with coolant, it started leaking. So i ended up using the M88 part, and had a heater hose from something that made a bit of a U turn and went over the head to the heater control valve.



This was much easier to access on the engine stand vs in the car....
At least its not leaking any more.


Here's that heater hose routing. Not bad really. It's pretty tight between the head and firewall anyway.

[mottati]

So where to put the battery? The SA 745i had the battery in the trunk, up behind the back seat. The spare tire prohibited it from being in the right rear corner, like on the M5/6. I did pull a long battery cable and positive mounting block out of an e32 in a pick n pull, but in the end, i noticed there was a perfect spot in the right front corner of the engine bay. It even looked like a battery tray, and had a hole for the OE battery hold down. Another plus, the old battery fit there perfectly, so there it sits.

[mottati]

Jay here on the board sent me a couple of wiring diagrams for the e23 and the M88. I had a little trouble finding an L jet e23 c10 pin out, so i stripped the old engines harness and just followed the wires to see what they did. Then i noticed the old Haynes manual sitting on my garage book shelf, and in there was a pretty good 'generic' L jet c10 diagram



So with my wiring "map" made, i put together the e23 C10 connector with the M88 wires.



And plugged it all in.



Wiring harness pulled into the cabin, and DME tucked up in the speaker well. The e23 DME usually mounts a little higher, but the e24 harness didn't seem to want to reach that car, and i didn't want to really make things tight on the wiring, so i mounted it lower, which will make it unlikely to fit a speaker in there.



Needed to run a fused 12v lead to the fuse box, and another to feed the DME.


Then it's time to double check, cross fingers, and connect the battery.

[mottati]

so i ordered a 'diy battery cable kit' since i needed to run the batt cable from the RF corner back to the starter, and have a couple of pigtails for the dme and fuse box. But in the mean time, i really wanted to get the engine started, as it was still a bit of an unknown. So i used the long cable i pulled from the junkyard just to hook things up.

And.... No sparks, no burning wires, no popped fuses. Good so far.



I did clean this up as soon as the new cable came in.

[mottati]

So it was time. Fire extinguisher ready. Turn the key, dash lights up as it should, engine cranks, no bad sounds, oil pressure light goes out, good. But no fire.

Wait a bit, try again, same result. I pull off the fuel feed hose. No fuel. Hmmm. Jumper the fuel pump at the relay, i can hear it running, crank, same result. Check speed and reference sensors, seems right. Then a thought pops into my head. OBC and CODE. My car has no OBC, the M635csi did, and i remember this little 3 wire pigtail off the dme harness that i had nothing to plug into.



My son has an 84 733, i look up under dash, yeah, that harness plugs into a harness that goes toward OBC. I call a friend who has a bmw shop, "oh yeah, i remember when we'd see those cars, they'd get towed in because the obc would fail, or the harness would get brittle, and you'd get no fuel, and no spark. You have to jumper 2 of those wires, but i can't remember which 2. I can check and let you know on Monday though."

So, i'm impatient. So i look at the ETM, and jumper the white and black. And it fires, but doesn't run.

https://youtu.be/dUd6VOBF8XU

DOH, i didn't hook up the AFM.

[tig]

Such a great thread. Loving following along!

[mottati]

Such a great thread. Loving following along!

Thanks your build threads were certainly inspirational.

[tschultz]

Great work -- the engine is looking very natural in that engine bay! I do love burgundy cars too.

Great progress too!

[mottati]

Great work -- the engine is looking very natural in that engine bay! I do love burgundy cars too.

Great progress too!

Thanks, yes the M88 looks quite at home in the e23. It's a pretty comfortable driver too. The M88 is much more refined than i expected. (as i mentioned in the beginning, i did this over the summer so the car has been on the road for a few months, just finally documenting the build here)

[ElGuappo]

I am loving this thread and can't wait to see this beast.

[mottati]

So I still didn't have the plenum on, but i plugged in the AFM, and propped the 'door' open slightly so it would get a signal as if air was flowing thru it, and started the car to let it run for a couple minutes.

https://youtu.be/mRDthR01l6I

No leaks, no bad sounds....time to get things buttoned up so i can get this out of the garage.

[tn535i]

How have I missed this before now. Great job.

The M88 is much more refined than i expected.

You know I feel that when I drive my M30 and S38 back to back. Maybe because my M30 has 300k on it and not so perfect exhaust but the S38 in my M6 just feels very different, smoother with less vibration even though the 'sounds' are louder. Some of that I attribute to the greater levels of materials to dampen sound and such in the luxury '6' over the '5'. Does the '7' have more of that also?

[ElGuappo]

My E23 is so much quieter than any E28 I've owned, the only E28s I've been in that can compete with a 7 are Darins 535 in San Diego and Devinders M5.
All the air seals are so much better, and there is at least double the amount of padding.

[mottati]

So with the plenum installed, the e23 coolant reservoir wouldn't fit.



I had a new e28 M5 reservoir, so i tried that.



Better but still not quite right. But a couple zip ties would at least make it work for now. I really wanted to get this out of the garage.



And, about 2 months after I started, i was pulling the e23 out of the garage under M88 power (with open headers of course). (and of course i forgot to remove the wheel blocks)

https://youtu.be/sQ-BtXYqIZk

[mottati]

You know I feel that when I drive my M30 and S38 back to back. Maybe because my M30 has 300k on it and not so perfect exhaust but the S38 in my M6 just feels very different, smoother with less vibration even though the 'sounds' are louder. Some of that I attribute to the greater levels of materials to dampen sound and such in the luxury '6' over the '5'. Does the '7' have more of that also?

I have a few s38s, a US spec 91 (3.6) and a 93 and 94 euro with 3.8's. The 3.6 is much lumpier than all of them, and even the 3.8's are a little different from each other, but the M88 seems to be the smoothest of the 4.

The e23 does seem to have more sound deadening vs my past e28 M5 (but not the e34's).

[Adam W in MN]

I just came across some photos of your car on my phone from the bringatrailer auction that I had saved because I liked it so much! Great to follow this thread but hoping you'll share some driving videos.

[Greg E34]

Very cool! Would love to see this in person.

[mottati]

So now i needed an exhaust. I'm in california, so besides passing a tail pipe test, the car needs to look OE. Oe enough at least, to get by a visual inspection by a tech who has probably never seen an e23, nor an M88. My plan was to use the US spec e28 M5 header, and catalyst. In my initial shipment, i was a bit disappointed to see what was supposed to be a US cat, had been cut up, and a small resonator welded in it's place. I did later find an OE lowish mile US e28 M5 cat to have on hand.

For the rest, i had a B&B triflow muffler that was welded to an e28 M5 center resonator, from a past e28 M5. My plan was to have this extended to fit the e23 chassis, so i could swap in the e28 front cat section. To get to the muffler shop, i bolted in the front 'resonator' and then cut the e28 / B&B system, so i could hang the center resonator in, to tone down the noise a bit. It was still pretty loud, but i could drive it to the muffler shop.



I have a muffler shop that i've literally used since i was a kid, same guys own and operate it for the past 35 years. It's fun going back, often with my boys' projects now. So I explained what i did, and what the goals were. They did a fabulous job extending the resonator section, welding on the triflow muffler, they even painted the mid section, and mounted everything really nicely. (everyone always loves the 'm6 engine in an old 7' idea).


Couldn't be happier with the looks and the sound. When on my old e28 M5, this droned, and was just too loud. I suppose the extra sound deadening helps on the e23, because it sounds great, and is very comfortable in the cabin, from a noise standpoint.

[Nebraska_e28]

I bet that resonator tames the B&B quite a bit giving it a perfect rumble. Looks great!

[mottati]

So it's running and driving, but it was not 100%. It had a pretty serious stumble off idle, and some light throttle misfire. WOT, it felt pretty good. It just felt lean on part throttle. I know people say to never mess with the AFM. I had this gone thru by bavarian restoration, and it was pronounced healthy, but I tinkered with the one on my son's 733 to get it to pass smog, and i was feeling confident, so i opened it up.



I noticed if i held the rpm at a steady 2500ish, and manually opened the AFM to simulate more airflow (and add more fuel), the engine really smoothed out, and sounded better. So i loosened the spring tension on the AFM (about 9 clicks!), and it was running great. After a fair amount of driving, the plugs look great. I'd like to either get a wideband on it, or run it on a dyno to make sure my AFR's are safe, but based on the plug appearance, i think i'm in the ballpark.

https://youtu.be/qgzd7wpHDlM


Then another diversion arrived. A friend of a friend who knew of a lightly crashed e34 M5 (wearing a dinan badge) that had been off the road for a while, and the wife wanted it gone. I couldn't pass it up, so....



After some pick n pull searches, finding black hood, grills, core support, and a bunch of deferred maintenance (and some new tires). My "winter" beater. I'm a sucker for e34 M5's.

[Tiit]

You are a legend. I wish I was your neighbour or something.

[mottati]

You are a legend. I wish I was your neighbour or something.

I'm pretty certain most of my neighbors don't feel that way!
Although i do have this one elderly guy who tries to save me, and tells my wife "he could be like me and spend his money on gambling and cheap women"....

[thugginrobby]

You are a legend. I wish I was your neighbour or something.

I'm pretty certain most of my neighbors don't feel that way!
Although i do have this one elderly guy who tries to save me, and tells my wife "he could be like me and spend his money on gambling and cheap women"....

Turbines... I want

[mottati]

Turbines... I want

I was thinking the turbines would look good on the e23....

[CSBM5]

You are a legend. I wish I was your neighbour or something.

No kidding! I'll live on the other side.

[Spen]

You seem like such a cool guy Super work!

[nismo2020]

Impressive stuff and garage... well done!

[mottati]

thanks for the kind words guys. Happy New Year. We're pretty much up to date, on where the car stands. I need to figure out what to do with the interior. It's the base spec cloth, kind of a chevron pattern, not the velour/corduroy stuff on the higher end models. The drivers seat is of course a bit beat up, outer bolster, seat cushion. I bought new horse hair padding (still available), but i'd like to maybe put some sports seats up front. I also found some tan houndstooth on eBay, and bought a few yards. Maybe houndstooth centers, leather bolsters. Not really sure yet.

Suspension has been maintained, so bushings, ball joints, tie rods etc are all good. It's stock euro springs and bilstein hd's currently. Front roll bar, no rear. Im thinking adding a rear bar from a 745, bigger front bar, maybe h&r springs.

Paint seems to be original. Top surfaces have some clear coat issues, the roof is the worst. Don't really want to do a full restoration, and i can clean it up and make it fairly presentable. Here's a couple of professionally done by Courtney Cutchen for a blog article for a local shop, Performance Technic. You can get a feel for the paint condition.

I'd like to do some lower front spoiler because it seems unfinished compared to, say, a 745. But at this point, i'm just giving it some part time driver duty, getting some miles on it, and getting more comfortable that i put things together correctly. I've got about 1500 miles on the swap since September when i drove it out of the garage for the first time. I need to make a more permanent mount for the coolant expansion tank, and the air filter box.






The full blog/story can be seen here: https://www.performancetechnic.com/blog ... amilystory
Mostly featuring my euro e34 M5s.

[muleskinner]

Car is looking great. I'd put it on a set of Style 5s or a set of staggered Style 32s, each of which gives it a killer look. As far as the spoiler, I"d color match it to the rest of the car. It would give it a really clean look.

[Adam W in MN]

I'm going to go read through your car collection write up and pictures now and cool that you're a fellow e34 M5 lover! I miss my 1994 E34 M5 3.8 liter, it was such a wonderful machine.

I agree on the staggered style 32 recommendation for the E23.