I look to the Subaru converters since there are many done. I know some are using stand alone engine management but I will use OEM ECU for now.

Did you use donor wiring, create all new wiring, or splice some into stock 914 wiring? If splice, what did you keep and what did you remove?

I've got the complete Audi S4 harness and diagrams so I "could" replace everything. I'll likely do that but I first need to remove unused circuits as they take up space.

My plan is:
-Sonu to help get the motor running by October
-Electric door windows
-Use Audi instrument panel and associated sensors
-climate control work including A/C

Audi parts I will not use:
-brake sensors
-air bags
-most emissions systems
-options

ZOIKS! thats alot of wiring to go thru....

I thought the whole reason behind having an older 70s sports car was to avoid things like ... excessive wiring. You can easily see now how newer cars have over 300lbs of wiring and electronics.

I'm building my interpretation of a new 914, I just don't have millions to develop an all new chassis and drivetrain so I am meshing old and new. Are you calling advanced fuel management, safety, and diagnostics systems "Excessive"? If you want simple get an earlier, say 50's or 60's sports car.

It was heavy but not that heavy. Maybe 25 lbs...

Calling them excessive? Aye, I am.

Go pull a main harness out of a new Benz. The guys next door love busting their knuckles on that stuff.

You only need as much as you need. The rest can keep the garbage can company. Trim it down to the essentials. The reason cars need so many safety and management systems is because most people are stupid, and even moreso behind the wheel of a car. That makes the car companies liable for not providing a safe enough vehicle, even though it was the idiot behind the wheel who decided to do something wrong and injur themselves, someone else, or damage property. Cars are a relatively safe item when driven properly.

/rant

I'm thinking of the easy HP Suby solution but would keep the spagetti to a minimum. Carbs would be cool if all it takes is to weld up some intake manifolds taking the cams would be good enough for crabs. All them sensors seem to be more of a pain than usefull.

I used almost all donor wiring. I did leave the 914 harness in place for the starter, oil pressure warning light, etc. A lot of wire can be removed, just spend some quality time with the wiring diagram to figure out what you need if you want the obd and mil to work.

I made a guesstimate of how long the harness needed to be and started shortening/splicing. My two recommendations are: 1- buy a dymo label printer, 2- give a good strong tug at every splice to make sure it doesn't want to come apart, on the suby some of the wire diameters are pretty small and have a tendency to get very weak when stripping the insulation. I found this out after the new harness was in the car, no fun.

I like all the sensors... plug in the code reader, 'XXXX input low', take a look at the sensor, 'ahh, i should have tightened that vss down a little better', all fixed. Troubleshooting skill- minimal... daily driver quick and easy to fix - yes.

Evan

Thanks Evan,

That's exactly the type of experience I was looking for!

Felix

My thread is a technical question but you're entitled to your opinion...

You are not going to believe how much of the original harness you will throw away. My harness that was created out of the factory harness is only about 5 pounds, and about 4 feet long.

Keith

Felix:
Ditto. My understanding is that the guys at Renegade take the stock harness and totally strip it down to only leave what is necessary; a very time-consuming project for sure. I'll let you know when I pick up 914aru and you're welcome to come over and check out the mods.
Later,

You still have all the "sensors" with carbs... except you have no way to tell they are working right.

The real benefit of having sensors wired up to an ECU is you can jack a laptop into the ECU and see exactly what's going on.. and on a good setup you should be able to see things that are in real numbers... i.e. if the coolant temp says 175oF you should be able to fire a pyrometer on a cooling pipe and see 175oF.

Carburettors do exactly the same thing, they just do a lot of mechanical tricks in order to make the same decisions, which generally means make more approximations (i.e. some strip of metal happens to expand at a similar rate to the warmup enrichment curve, so we'll have it push this lever... On a megasquirt you just draw the curve on screen, and you can see the instantaneous effect on the mixture.

I made a harness for my Subie conversion (which uses megasquirt) and brings all the wiring into the cabin (MS is between the seats). I think it's simpler than the stock D-jet harness.

To answer the original question - I spliced the stock wiring with my own wiring. I stuck a couple of large connectors on the end which plug into sockets that are mounted to the firewall.

Anyone doing Subie conversions with stock ECUs may also check out the OpenECU project online - they are working on reverse engingeering the stock ecu, and have a usb cable for talking to it and changing parameters. Lapuwali and I ran into a guy on the Alpine500 who had tweaked his WRX map so it ran a lot better in the mountains using their stuff....

Ha ha!

ha

eh

that looks like its gona suck...

GL... Wiring is not my forte yet...

Wow, you have a great technical mind bro. I realy don't have much problems with wiring but the whole technology side of the conversion is a little above my head. I guess I'd need to be with someone who has all the knowledge like yourself and I looking and learning. To get your PC to get the injectors to squirt on command would be so cool. I could get into this stuff. I wish there was a manual for this conversion.

My general take on this is that you'll want to completely pull 100% of the wiring out of the engine bay when doing any engine swap. The only wiring still there should be the stuff that goes to the rear trunk.

Nearly 100% of the center tunnel wiring should also be pulled. What you NEED out of the stock wiring in the center tunnel is the big unswitched battery wiring (red wires), a single small (18g is plenty) switched power wire, the starter wire, and the rear trunk wires (brake, tail, turn).

The switched power wire should go to a relay that provides power to the ECU and the engine. I would pull the relay board, the relay board supports, and put the ECU in a waterproof box in the engine bay. This minimizes the amount of wiring that has to run back up to the dash. Another common option is mounting it all behind the passenger seat and running the wires right through the firewall. You'll need wiring for any gauges you decide to run, and those should pretty much be the only additions to the center tunnel wiring.

Leave most of the dash and all of the front trunk wiring alone. The harnesses all split this way pretty neatly, so you should be able to separate out the front, center, dash, and rear sections pretty easily.

The ECU has a nice stock waterproof enclosure.

I'll do that but will use the stock Audi instrument cluster and climate system so that harness goes too. The big dilema is to use keep the wiring for the stock turn signals until future plans to adapt the Audi column stock controls later.

Any suggestions on creating new chassis ground? On my V8, I drilled a hole for a small bolt and used star washers on both sides of the sheetmetal after grinding the paint away. I've read that for sensitive electronics, a full ground loop is preferred over using the chassis as the ground return.

Good input guys, THANKS!

Felix

Run a 10g brown wire from the battery negative post to a bolt under the dash somewhere. Or, just grind off some paint, drill a hole, solder a bolt to the body through that hole, then paint over everything but the bolt's threads.

With a conversion as extensive as yours I'd strongly consider completely rewiring the car. My remarks above were more general. Since you're going to remove the stock headlights, and I presume the headlight buckets and whatnot, I'd just remove everything around there. The turn signals are a single wire per light, or two wires if you're also doing parking lights. You're going to redo the turn signal buckets extensively, too, so there's no win in keeping the stock wiring. Esp. since you're making a show car, you'll want all new wire, as a lot of it will be visible, and you want it neat. It will be difficult to get the wiring neat if you use a harness from some other car.

I am about 99.% finished with the wiring for my conversion. Only things left are relays for the radiator fans and wiring in the alternator.

I am using the stock ECU and the stock wiring harness. What I did was go through the wiring diagram for the Subaru and made a spreadsheet for every ECU input/output and from there decided what was useful for me and what was not. There were a few things that I didn't care about, mainly smog related stuff and fuel tank stuff. All of those things are simulated in a small printed circuit board I made up which has a bunch of potentiometers. That box sits atop my ECU for the shortest possible wiring.

The erst of the wiring comes out in I believe 5 cable assemblies organized by use. two go to the engine, another to the oxygen sensor, and another two go to me engine bay box. One of those is strictly for power, the other is for the atmospheric pressure sensor and radiator fan controls.

Inside the engine bay box, the 914 harness (which is mostly intact) splices off to the rear trunk, and also to the ECU harnesses. There is a relay for the fuel pump inside the box, the atmospheric pressure sensor, and 4 fuses. Several of the stock 914 wires are unused, but I'm leaving them there because they don't take up much space/weight and might be useful for other purposes later on.

So the real key here is spending a good amount of time with the wiring diagrams and figuring out what EVERY wire does. This took me quite a while. Aside from the engine bay prep work I've done,the wiring was the single most time consuming part of the conversion.

So get the diagrams, cut out what you don't need (I cut probably 75% of the whole Impreza's wiring out) and leaev those ends long enough that if you messed up, you can connect things later on. I left those wires at elast an inch long from the conenctors and coverd them with shrink tubing to prevent shorts.

Rewiring the car is definitely an option. I almost did this with the other car I was converting, but decided it was too much extra work. There are other complicating issues here too, such as finding good multipin connectors (12 pin weatherpack I _think_ is the most you can find easily) and the cost of building a wiring harness from the ground up (pun intended) can be substantially higher than you might think.

-Tony