I knew I should have been making mounting brackets for the connectors in the last days before driving season started but I didn't want to lose those extra days so I zip tied to the hard points like fuels rails as the factory does. It's stayed that was so far - other priorities and other projects took over since it was "good enough".
@911Ren20 If you are interested, JReady makes mounting clips for Deutsch DTM DTP and DT size connectors. Definitely better than zip ties!

Since I wasn't re-wiring the rest of the car, I also sourced power from the old CDI power source.

Actually, I think the way you’ve added connectors is probably easier than what I did. I spent a lot of time figuring out how to manage the wiring without splices, and organizing everything to avoid connectors was definitely a challenge.

That said, it’s worked out well — I can drop the engine and secure about 90% of the harness up on the right side of the engine bay. There are a few outliers (starter motor, alternator main and field wires, and the brake light connector on the left), but overall it’s pretty clean. And if you’re pulling the engine for any serious work, you’re likely removing most of the wiring anyway.

My main hesitation with connectors is reliability. Every splice or connector adds a potential failure point. I’ve had issues before — wires not fully seated in connector bodies, plastic tabs cracking — and in one case, it was a brand-new avionics install in a plane I owned. That one took forever to diagnose, and it left an impression.

With these cars, my biggest concern is the shielded cables. Are there truly reliable shielded connectors for those? The cam and crank sensors each carry four wires inside a shield, and signal integrity there is critical.

Edit
This was reported a couple of days ago.
Loose Wire on Containership Dali Leads to Blackouts and Contact with Baltimore’s Francis Scott Key Bridge
https://www.ntsb.gov/news/press-releases/Pages/NR20251118.aspx

Valid concerns for sure, and that’s why I build my own harnesses: so I can double check that every pin is seated, every wire properly crimped, etc…

As for shielding- all you have to do is run the shielding through a pin and the integrity is maintained- that’s what’s done in high end motor sports. So for a cam sensor with 3 wired, use a 4 pin connector and a wire from one side’s shielding to the other. Easy.

I get that the shield continuity is maintained through the connector. But at that point, if you're using a standard connector, the shield isn't surrounding the wires. Are you using a shielded connector? We had some barrel type shielded connectors on a project. They looked like these:https://www.mcmaster.com/products/shielded-cable-connectors/

With the Haltech harness, it's only terminated at the ECU. You're still got all the work of making up the bitter ends. One big advantage is that each wire is color coded. The bundles are broken down into sub-groups for injectors, ignition, etc.
http://forums.pelicanparts.com/uploa...1763642581.jpg

Haltech's setup is very nice and their organization is top notch. The more I look at their offerings them more I wish there were just a few things that were different as I'd love to use their ECUs.

I'm using MS3Pro Evo+ and I buy my wire bundles from AmpEFI who makes the ECU. They're all color coded, organized and grouped as well. That said, you can use wirepro, wirecare or any of the online sellers of TXL wire to buy and build your own bundles. If I ever do this again (gosh I hope it's not every year!) that's what I'll do and I'll get all my favorite pretty colors ;)

Keep in mind that the shielding on the twisted cables ends an inch or two before the sensor and an inch or three before the ECU so it's not inconsistent to have an inch in the middle not shielded. It's not going to render the shielding useless.

I spent a bunch of time (needlessly?) reading TE Connectivitiy's white papers on motorsport cable (they invented the concentric twist that incorrectly everyone calls "Mil-spec") and they recommend grouping all the shielded cables into the core of the bundle, grounding all the shielding into the ECU's drain, and running power separately to minimize any chance of interference.

I paid for a subscription to HP Academy so I could access some of their courses. They also have a lot of free articles. Here's one about exactly what you've described about concentric twisting wire bundles.

https://www.hpacademy.com/technical-articles/the-truth-about-concentric-twisting/

Really appreciate the healthy back and forth on shielding and connectors.

I am leaning toward a hybrid approach: keep the critical shielded runs on a direct route, and put the rest of the engine wiring on bulkhead connectors at the firewall. That way crank and cam pairs stay as clean as possible, but injectors, COPs, fans, pressures, temps, etc. can all live on a sub harness that unplugs when the engine comes out.

With the way Haltech lays out and labels their harness, plus a decent pin map, I do not think the bulkhead adds much complexity for a DIYer. It just buys some future proofing so the next round of changes doesn't require too much effort. (dreaming)

My current set back is that a few key parts are back ordered until mid December, including the ECU, so I am mostly in engine prep and planning mode for now.

Please keep the experience and best practices coming. A lot of threads show the finished product, but this level of detail on how and why to build a harness is great for DIY folks like me.

Great notes from everyone!

I hope some of these thoughts are helpful to anyone interested in EFI conversions.

Ignition timing always reacts faster than airflow change when it comes to idle control. Depending on reaction time of the idle bypass valve or the ITB intake cross section area it can be problematic to have stable idle in closed loop using air only (especially with radical valve timing) so closed loop ignition control with open loop DBW or idle control valve is a good the way to get great oem like idle, or closed loop for both but having ignition doing most of the heavy lifting. BMW factory first gen DBW variant ITBs still retain an external air bypass or idle control valve and keep the blade opening static for idle control.

Knock control.... It becomes easier to tune the knock control strategy when the knock sensor is not mounted on the heads nor the rocker boxes. If a knock bridge will be implemented it should be on the bottom of the cylinder as originally implemented by Porsche. There are some aftermarket cylinder choices that have that mount available even if the motor pre-dates it.

As far as knock sensor being mounted on the throttle plate stud, it is not perfect but I prefer it to the bridge mounted on the heads or rocker boxes. I have used it with enough success that I could implement individual cylinder ignition tuning on both banks to get closer to MBT than otherwise achievable and was worth 20 more hp on the last car I tuned with knock control properly calibrated vs just gross knock control (My personal 8k rpm 3 liter). After ignition timing calibration was settled I have the Maxxecu monitoring and adjusting any timing needs from knock by individual cylinder as well.

I have a firewall mount for a mil spec connector that I make and supply that will allow clearance for a booted 90 degree on the cab side that works nicely if you feel like you wanted a single connection point when mounting in cabin (engine bay mount will work but I prefer in cab mounting) It will retain the rear seats and sits near the shock tower driver side. It is made in aluminum and is gasketed on both sides to seal the engine bay from inside the cab.

http://forums.pelicanparts.com/uploa...1763664246.jpg

http://forums.pelicanparts.com/uploa...1763664246.jpg

http://forums.pelicanparts.com/uploa...1763664246.jpg

If a Mil spec connector wont be used and you do a straight run I recommend to plan for a junction or Deutsch DT or DTM connection for each bank of ITBS to make future servicing easier and depending on your ignition control plans there as well. The Deutsch DT series connector is is rated for way more connect and disconnect cycles than most other OEM style connectors and will make for quicker work when removing the engine if you don't use a single disconnect.

RB racing is a great resource on wiring that is published for free, it is worth the time to look at.
https://www.rbracing-rsr.com/wiring_ecu.html

Dealing with braided/shielded wire, https://www.youtube.com/watch?v=Ip1ZrR1qdHM
This video has good examples and shows some methods to terminate the shield so it can pass through on your chosen connector. I dislike the shrink/solder as there is a lot of junk out there copying the good stuff and it makes for a bulky termination usually. If using quality splices, the proper crimper and strain relief it will never cause an issue.

I prefer using a head temp sensor over using a breather cover or timing cover as a source of engine temp for fueling strategy when possible. If it is a clean slate engine build I like to machine a solid part of the head vs using a clamp onto the fin solution. If the ecu/ems has thermocouple inputs I like using a ring terminal K-type as its the easiest to machine for (less invasive). In this example I used some brass to help make everything more temp stable and with some thermal paste as well.

http://forums.pelicanparts.com/uploa...1763664877.jpg


One last thought, try to remote mount any pressure transducers used whenever possible. When direct mounted to the motor the vibration will cause premature failure. This example is a fuel pressure transducer remote mounted with a -3 AN connection.

http://forums.pelicanparts.com/uploa...1763664965.jpg

I ended up with EMU Black because my first choice Haltech had a six month back order on ECUs. If I stayed with it, I would have ended up building through the driving season which was not a compromise I was willing to make. EMU also has the colour coded and labeled flying lead (I think most ECUs have them) and supplied the the shielded wires, all long enough to run along the old lambda sensor routing to the left side of the engine bay. Not going with Haltech did leave me with zero local support with EMU which was the compromise I was willing to make.

Your idea for future proofing sounds sensible.

Good discussion here. Don’t hesitate to build your own stand alone harness. I built my first one by reading posts here and watching YouTube along with a $50 or so subscription to Evans Performance Academy. ECU Master Black flying harness and these tools and Deutsch DT (mostly), some DTM connectors, along with a couple of orders with WireBarn . Com for pretty 20’ lengths of various gauge and random colors. Everything was simple if you do it one item at a time and make good notes for future reference. You can see this in my build thread. I loved wiring and had never done it before this project. Even built my own fuse box with relays. A lot of fun! Patrick

http://forums.pelicanparts.com/uploa...1763857276.jpg

Rivet, Thanks for sharing those tips.

For CHT, are you just using the ring type? Would ming sharing the part #? You just drilled and tapped the threads into the fin? Assuming that's Cylinder 3?

For intake air temp senor. There are screw on type that uses a bungs that i can weld to the filter box base plate. Or simply a press in type that I can just drill hole, add grommet and press on to the plate, less work?

Thank you for the encouragement. this is the route I will take. following everyone's foot steps.

I am prepping the engine for sensors and all the various bits at this point. progress is slow. Parts are also back ordered due to holiday rush.