Wire Harness Thinning Thread

[spxxx]

Seems like this topic is coming up more often as many of the maniacs left here are chasing tenths and therefore also ounces of weight.

Anyone have tips / tricks / low hanging fruit?

Which modules can be pulled?

Which wires are critical in the large main driver side loom?

Sub-3k or bust!

[amg6975]

If you don't want/need airbags that is by far the lowest hanging fruit. I'd bet nearly half the wire in the car is for the airbags and sensors.

In the KOMBI, code SFY_ALIVE_ZAEHLER and SFY_ID_MONITOR to nicht_aktiv then just unplug the ABG module and trace all the wires back to where they originate and remove them. Don't' forget to remove the airbag in the dash... it's heavy.

If you have race seats you can trace all the seat wire back to where it originates and remove it with no consequences. Same with the combox, amplifier/speakers, and FZD roof module.

My methodology was to just unplug stuff, code it out, make the car happy, then just pull all the wire out that goes to that particular connector then move on to the next thing.

[spxxx]

Originally Posted by amg6975

If you don't want/need airbags that is by far the lowest hanging fruit. I'd bet nearly half the wire in the car is for the airbags and sensors.

In the KOMBI, code SFY_ALIVE_ZAEHLER and SFY_ID_MONITOR to nicht_aktiv then just unplug the ABG module and trace all the wires back to where they originate and remove them. Don't' forget to remove the airbag in the dash... it's heavy.

If you have race seats you can trace all the seat wire back to where it originates and remove it with no consequences. Same with the combox, amplifier/speakers, and FZD roof module.

My methodology was to just unplug stuff, code it out, make the car happy, then just pull all the wire out that goes to that particular connector then move on to the next thing.

That was my plan, start with radio stuff then airbag and safety components but was worried about coding the airbags as I wasn't sure what would happen when the impact sensors were removed. Still have my full headliner and curtain airbags.

Any idea of dashboard airbag weight? Pulling the dash sounds painful but would be an excuse to move to a single hump.

Thanks!!

[amg6975]

Originally Posted by spxxx

That was my plan, start with radio stuff then airbag and safety components but was worried about coding the airbags as I wasn't sure what would happen when the impact sensors were removed. Still have my full headliner and curtain airbags.

Any idea of dashboard airbag weight? Pulling the dash sounds painful but would be an excuse to move to a single hump.

Thanks!!

Not sure about the weight of the dash airbag. You will want to remove the dash to fully thin the harness, I don't think you can do it with it in place.

You' can't remove any airbag sensors if you still have some airbags. I don't think you can code off individual sensors. There are so many checks around the airbag module it's crazy. Even if you code off stuff and it thinks you should have them it just turns them back on and gives you an error.

The only thing the rest of the car cares about is the KOMBI checking in on the ABG to see how things are going. The two lines above stop that from happening so the KOMBI will never know the ABG isn't there.

[roastbeef]

the passenger front airbag can be removed without removing the dash its held in place with four (probably 10mm if i remember correctly) nuts. the bolts are semi-permanently molded into the dash, and you can cut them out for additional weight loss. you just have to remove the glove box to remove the airbag.
the airbag weighs about 5lbs.

and taking the dash off isn't a big deal. its a couple of plugs and a few nuts and bolts.

[spxxx]

Originally Posted by roastbeef

the passenger front airbag can be removed without removing the dash its held in place with four (probably 10mm if i remember correctly) nuts. the bolts are semi-permanently molded into the dash, and you can cut them out for additional weight loss. you just have to remove the glove box to remove the airbag.
the airbag weighs about 5lbs.

and taking the dash off isn't a big deal. its a couple of plugs and a few nuts and bolts.

Good to know! Definitely on the list.

Thanks for sharing, I'm still TBD on pulling all curtain airbags this round or waiting until the full cage goes in.

[amg6975]

Not pulling the airbags will greatly reduce what you can take out of the harness. Like I said I would bet that almost half of all the wire in the car is for the airbags and sensors.

[spxxx]

Originally Posted by amg6975

Not pulling the airbags will greatly reduce what you can take out of the harness. Like I said I would bet that almost half of all the wire in the car is for the airbags and sensors.

Yeah that's right, I was thinking that a majority of the wiring was radio related with how big the driver side loom is which ends at the amp/Bluetooth module. I assume the Bluetooth module in the trunk can be removed without issue (since iDrive is already removed).

The airbag module is under the back of the arm rest correct?

[amg6975]

Originally Posted by spxxx

Yeah that's right, I was thinking that a majority of the wiring was radio related with how big the driver side loom is which ends at the amp/Bluetooth module. I assume the Bluetooth module in the trunk can be removed without issue (since iDrive is already removed).

The airbag module is under the back of the arm rest correct?

Yes, all of the audio stuff can be yanked out. Code the KOMBI COMBOX_ALIVE_MONITOR and COMBIX_ID_MONITOR to nicht_aktiv and you won't get SOS warnings. You can/should also remove 6VC from your VO. If you remove the head unit the MOST stuff won't work and Ethernet on the OBD port won't work but I don't think that has any consequence if you don't have iDrive or any other audio things.

ABG is indeed right behind the ebrake handle.

EDIT: of note, the ABG module has an internal accelerometer for roll-over detection so don't unbolt it without disconnecting power. If you flip it and it thinks you're in the car you're gonna have a bad time.

[bigjae1976]

Start with a clear understanding of what you are willing to give up.

For example, its a BMW, I'm a BMW driver so I don't need turn signals but I want my windows to work. So in the case of my E46 - I need zero comfort and convenience so I can lose everything.

Looking back, I'd start with the obvious stuff - radio and airbags. Then move to the footwell module. Unplug it, drive the car and see how the car behaves. Keep unplugging other modules until you get to where you want.

Remove the harness and minimize wire cutting since you MIGHT have to put it back in and also makes things sellable. If you don't care...cut away. Temporarily wrap, install and test. Repeat until you remove as much as you want.

I'd also identify any BUS circuits so you know what wires to bridge if you unplug a module and lose a bunch of other stuff that you want to keep.
You'll want a lot of this...

https://www.amazon.com/XFasten-Harne...zcF9hdGY&psc=1

I used a thinner width version to temporarily wrap the harness when testing.

I would absolutely do all the wiring harness thinning I possibly can before installing a cage or roll bar. At that point, wiring harness work becomes much more challenging.

[DRLane]

I’d also note, given your sub 3k or bust goal spxxx the complete wire harness from end to end only weighs ~59 lbs.

I know this because I pulled and labeled the entire harness from my 08 e92 (with most of the options including sunroof, drive) except DCT. That’s from the rear taillights, through the firewall to headlights but not including the underside battery cable.

I sent this to Germany and the 24”x24”x24” box weighed in at 62lbs. Had Martyn from Project Rogue thin it down retaining only the driveline and light components necessary. Don’t have an updated weight but will share once I do.

This means a significant portion of the 40-50lb weight savings you see posted with harness thinning is the modules, plastic brackets, metal brackets, etc. It’s not just a jumble of wires…

https://youtube.com/shorts/i6jrddnxPKI?feature=shared

[bigjae1976]

Originally Posted by DRLane

I’d also note, given your sub 3k or bust goal spxxx the complete wire harness from end to end only weighs ~59 lbs.

I know this because I pulled and labeled the entire harness from my 08 e92 (with most of the options including sunroof, drive) except DCT. That’s from the rear taillights, through the firewall to headlights but not including the underside battery cable.

I sent this to Germany and the 24”x24”x24” box weighed in at 62lbs. Had Martyn from Project Rogue thin it down retaining only the driveline and light components necessary. Don’t have an updated weight but will share once I do.

This means a significant portion of the 40-50lb weight savings you see posted with harness thinning is the modules, plastic brackets, metal brackets, etc. It’s not just a jumble of wires…

https://youtube.com/shorts/i6jrddnxPKI?feature=shared

I think the wiring will add up to more than you think. But removing the modules AND the brackets AND the hardware also adds up.

Really need to think ounces if the goal is optimizing weight loss. Again - understand the goal. An oz here and and an oz there...it all adds up.

You should be able to find at least 50 small things that you can remove that are an oz or two and are easily removed (hardware, wire, connectors, etc)...that's 3 lbs right there! Do that a couple of times and then you're talking about a significant amount of weight.

[spxxx]

Originally Posted by DRLane

I’d also note, given your sub 3k or bust goal spxxx the complete wire harness from end to end only weighs ~59 lbs.

I know this because I pulled and labeled the entire harness from my 08 e92 (with most of the options including sunroof, drive) except DCT. That’s from the rear taillights, through the firewall to headlights but not including the underside battery cable.

I sent this to Germany and the 24”x24”x24” box weighed in at 62lbs. Had Martyn from Project Rogue thin it down retaining only the driveline and light components necessary. Don’t have an updated weight but will share once I do.

This means a significant portion of the 40-50lb weight savings you see posted with harness thinning is the modules, plastic brackets, metal brackets, etc. It’s not just a jumble of wires…

https://youtube.com/shorts/i6jrddnxPKI?feature=shared

Thanks for sharing, I have a lot of low hanging fruit left to pull (airbag module, curtain airbags, entire headliner for that matter, AC is tempting with it's forward location too) and figured this would be a good place for knowledge sharing since it's such a rare project and the businesses building E9x racecars obviously aren't going to share everything publicly.

I wonder if there's much benefit moving the battery into the passenger rear footwell area to shorten the massive 12v wire.

I'll likely focus on the driver side loom that runs to the amp/Bluetooth module once I've pulled the modules/headliner & lower hanging fruit

[DRLane]

Originally Posted by spxxx

Thanks for sharing, I have a lot of low hanging fruit left to pull (airbag module, curtain airbags, entire headliner for that matter, AC is tempting with it's forward location too) and figured this would be a good place for knowledge sharing since it's such a rare project and the businesses building E9x racecars obviously aren't going to share everything publicly.

I wonder if there's much benefit moving the battery into the passenger rear footwell area to shorten the massive 12v wire.

I'll likely focus on the driver side loom that runs to the amp/Bluetooth module once I've pulled the modules/headliner & lower hanging fruit

Totally, and happy to contribute where I can. Yes you can shorten the cable way up and plant the battery in the passenger foot well. Lots of examples here. I’m moving all weight items I can toward the rear axle for better weight distribution and grip. A lot of the weight ends up coming from the rear and I’d like to insert it there if I’m pulling it.

Weight relo: moving driver seat position a ~ 12” back, electric power steering pump, battery, fire suppression. I think that’s it.

[DRLane]

Originally Posted by bigjae1976

I think the wiring will add up to more than you think. But removing the modules AND the brackets AND the hardware also adds up.

Really need to think ounces if the goal is optimizing weight loss. Again - understand the goal. An oz here and and an oz there...it all adds up.

You should be able to find at least 50 small things that you can remove that are an oz or two and are easily removed (hardware, wire, connectors, etc)...that's 3 lbs right there! Do that a couple of times and then you're talking about a significant amount of weight.

1000% this is the way.

[bigjae1976]

Originally Posted by spxxx

Thanks for sharing, I have a lot of low hanging fruit left to pull (airbag module, curtain airbags, entire headliner for that matter, AC is tempting with it's forward location too) and figured this would be a good place for knowledge sharing since it's such a rare project and the businesses building E9x racecars obviously aren't going to share everything publicly.

I wonder if there's much benefit moving the battery into the passenger rear footwell area to shorten the massive 12v wire.

I'll likely focus on the driver side loom that runs to the amp/Bluetooth module once I've pulled the modules/headliner & lower hanging fruit

You can relocate the battery but most sanctioning orgs have rules especially if it’s a lithium ion. NASA has some specific rules.

I use a lithium iron phosphate battery which isn’t subject to the same rules…also harder to find.

You might want to leave the battery alone for now until you get the low hanging fruit for weight distribution purposes. As you pull out weight you’ll notice the effect of 10-15lbs more and more.

If you delete a bunch of modules then you can use an aluminum wire for the battery. Aluminum has a higher resistance but is much lighter. Knukonceptz.com sells aluminum wire in 8-4-0 gauges.

[amg6975]

Leave the battery. The rear is plenty light already. I made a bracket and used a much smaller H size Lead Acid battery and have no issues. H3 maybe?

lots of small gains is definitely the right move. I was in the board of "oh it's just 20 lbs here and there but just went through everything with a fine tooth comb and found 200lbs.

The battery, wire harness, headlights (replaced with Halogens,) A/C compressor, etc. My car is still very livable on the street at 3200lbs w/DCT and most people would have no idea how much effort went into adding lightness. Still has carpet and sound insulation. It adds up in a hurry.

[spxxx]

Yeah I'd much rather keep weight out back, unless I'm able to pull massive weight from the front. HVAC etc still won't balance out the F:R ratio enough for it to be worth the hassle.

I'm just debating the pain of pulling my cage to get the headliner and airbags out.

Anyone have an idea of the headliner/curtain airbags aggregate weight?

[DRLane]

Originally Posted by spxxx

Yeah I'd much rather keep weight out back, unless I'm able to pull massive weight from the front. HVAC etc still won't balance out the F:R ratio enough for it to be worth the hassle.

I'm just debating the pain of pulling my cage to get the headliner and airbags out.

Anyone have an idea of the headliner/curtain airbags aggregate weight?

It’s not much… Definitely pull the cage out so you can take your time and have space to drill the rivets, remove the airbag modules, and the headliner and related pillars covers.

Maybe 10lbs?

Did you remove all the standard seat belt components?

[spxxx]

Originally Posted by DRLane

It’s not much… Definitely pull the cage out so you can take your time and have space to drill the rivets, remove the airbag modules, and the headliner and related pillars covers.

Maybe 10lbs?

Did you remove all the standard seat belt components?

Oh yeah everything is gone except HVAC and headliner/airbags. Well I have the dash and center console too.

[DRLane]

Originally Posted by spxxx

Oh yeah everything is gone except HVAC and headliner/airbags. Well I have the dash and center console too.

Then yeah, might as well clean it up and remove those pesky curtains and headliner.

[tsk94]

Originally Posted by DRLane

Then yeah, might as well clean it up and remove those pesky curtains and headliner.

Nothing more enjoyable then drilling out all those spot welds for the curtain air bags...