heinzboehmer's 2002 Topaz 6MT Coupe

[heinzboehmer]

Brackets are back and, unfortunately, I think I made the wrong call by going with paint.



This specific paint is too glossy and I feel like it just screams "look at me!". Not a fan of flashy stuff. But whatever, it's a part hidden in the engine bay, who cares.

The real problem is with the mechanical properties of the paint. It didn't seem to adhere properly and most of what was under the fasteners ripped off when torquing. It also feels extremely squishy and I do not trust that these parts will stay torqued like they should over time. I don't know if this was caused by poor prep, by the "high temp" paint, by the paint having been laid on too thick or by all of the above.

I would love to powder coat these parts and get it over with, but I'm afraid of accidentally annealing the strut tower brackets during the cure step. I think cerakote makes some low temp stuff, so will probably end up looking into that.

Sigh...

[karter16]

Brackets are back and, unfortunately, I think I made the wrong call by going with paint.



This specific paint is too glossy and I feel like it just screams "look at me!". Not a fan of flashy stuff. But whatever, it's a part hidden in the engine bay, who cares.

The real problem is with the mechanical properties of the paint. It didn't seem to adhere properly and most of what was under the fasteners ripped off when torquing. It also feels extremely squishy and I do not trust that these parts will stay torqued like they should over time. I don't know if this was caused by poor prep, by the "high temp" paint, by the paint having been laid on too thick or by all of the above.

I would love to powder coat these parts and get it over with, but I'm afraid of accidentally annealing the strut tower brackets during the cure step. I think cerakote makes some low temp stuff, so will probably end up looking into that.

Sigh...

I was really surprised when I got my rear RACP bar powder coated. The guy asked what I wanted and I said gloss black, and he looked at me and said “are you sure?” And showed me gloss black, and I thought it looked good. Then he showed me “satin semi gloss” and it was better, then he showed me matte and that was the best of the lot. Very similar to the OE stock strut bar finish so that's what I went with.

I thought the temp for annealing was quite a bit higher than powder coating temps?


Sent from my iPhone using Tapatalk

[bigjae46]

Brackets are back and, unfortunately, I think I made the wrong call by going with paint.



This specific paint is too glossy and I feel like it just screams "look at me!". Not a fan of flashy stuff. But whatever, it's a part hidden in the engine bay, who cares.

The real problem is with the mechanical properties of the paint. It didn't seem to adhere properly and most of what was under the fasteners ripped off when torquing. It also feels extremely squishy and I do not trust that these parts will stay torqued like they should over time. I don't know if this was caused by poor prep, by the "high temp" paint, by the paint having been laid on too thick or by all of the above.

I would love to powder coat these parts and get it over with, but I'm afraid of accidentally annealing the strut tower brackets during the cure step. I think cerakote makes some low temp stuff, so will probably end up looking into that.

Sigh...

Blast and then anodize? Powder coat will also chip off under and around the bolt heads.

Carbon fiber would look better :P

[maupineda]

Heinz, all these needed was a can spray. You should have taped the bearing surfaces.

I’d leave as is. Painting is fucking annoying, and sanding 1k times more.

Since they are fresh get paint removal and see it comes off if you want to redo them

the aircraft paint remover works good

[heinzboehmer]

I thought the temp for annealing was quite a bit higher than powder coating temps?

Maybe annealing is not the most precise word to be using here. What I mean to say is that I don't want to significantly affect the yield strength of the material by exposing it to higher temps than it will see in the engine bay. Thermocouple data says that the parts will likely never see above 90C, so anything past that requires scrutinization, to keep the brain happy.

Was looking into this last night and found a bunch of literature on AlSi10Mg (e.g. 1, 2, 3, 4, 5, 6).

With a bit of biochemical neural networking (i.e. lots of switching tabs to compare results ), I've arrived at 150C being the max "safe" temp I'd like to expose the alloy to. A bit conservative, based on some of the results in the papers, but I don't have a way to test the parts to failure, so would rather stay on the safe side.

Seems like powder coating cure temps are closer to 200C and I really don't trust some random shop to not crank the oven up arbitrarily, so that's why that process is ruled out. Other more common alloys (e.g. 6061) seem a little less susceptible to those temps, but strength still drops fast as the temp starts climbing.

Blast and then anodize? Powder coat will also chip off under and around the bolt heads.

This was gonna be my next approach, buuut then I reached out to the guy who cerakoted my brake calipers and was informed that there are some formulations that can fully cure and bond to aluminum at just 82C.

I have not treated my calipers with any care at all and the finish still looks brand new. I've smacked wrenches/wheels/rocks into them and have hosed them down with brake cleaner plenty of times, but have yet to affect the coating.

Here's a pic I took a few minutes ago:



Calipers are disgusting and have been bathing in track pad dust for a while, but the cerakote is showing no signs of wear.

Agreed that coatings will likely still chip under bolt heads given enough time, but as long as they don't do this during the first torque cycle, I'll be happy:



I'm essentially trying to replicate the durability of the BMW paint/coating. It does chip away with time under bolts heads, but it doesn't fail catastrophically.

Heinz, all these needed was a can spray

I do agree, buuut:

Painting is fucking annoying, and sanding 1k times more.

I absolutely hate painting stuff. It never comes out how I want it to and prep is so boring to me. I thought if I outsourced this, I would get a better finish and also have to do zero work. Not sure I was in the right here, though.

I did think of taping the bearing surfaces, but figured that if BMW got away with painting them, I could too. Also, I thought the parts would look a little weird with unpainted surfaces, since some of them are rather large.

I'm pretty confident the cerakote will work out well. My brake calipers have taken a beating with essentially no wear.

[heinzboehmer]

Yikes:



I'm glad I didn't drive with these installed. Not sure my alignment would have held.

Going for cerakote soon.

[0-60motorsports]

Cerekote will be really nice

[heinzboehmer]

Agreed! I'm excited to get the parts back. They should look very similar to how they came from factory.

I might have snuck in another engine bay component to get cerakoted as well

[heinzboehmer]

Few updates:

Update 1:

Cerakoted parts are still not ready. Supposedly get them back end of the week.


Update 2:

With Ted's guidance, I was able to get D Bus -> I Bus message relaying working. The third and sixth messages below were relayed from D Bus, with `DE AD BE EF` being the payload.



This is what I sent over D Bus:

BB 07 DE AD BE EF 9E

It's essentially just a normal DS2 command (first byte is destination, second length, last checksum and the rest are the payload) that gets routed by the IKE to I Bus if the destination is on that bus.

Next step is to figure out how to get Gauge.S to send these messages out on demand. Ideally, I'd like to program in event-based sending, but not sure if that's possible. Will investigate.

The other thing I noticed is that the IKE relaying is super slow. I played around with sending the D Bus message at different frequencies (all the way from a couple Hz to a couple hundred Hz), but the fastest I saw the relayed message pop up on the I Bus side was at ~1 Hz. I can't imagine tools like Inpa are operating at speeds that slow, so I'm hoping that I was just overwhelming the IKE. Again, will investigate.


Update 3:

I managed to get my hands on some unobtainium:






A never installed, NOS, 2021 production date euro slicktop headliner, courtesy of ridebikes. Incredible!

Gonna be kept in storage until I get the carbon roof project going, but I did do one thing before putting it away:



Can check out the scan here, if you're curious: https://s.digital3dcloud.com/space/f...5-eb2c04e8a802

Interesting to see how different the euro part is to the USDM one, especially from the back. Here's an internet picture of the USDM headliner, for reference:



This makes me think that the foam and aluminum honeycomb structures are there for crash safety and not NVH, like I originally thought. Maybe it has to do with the extra US regulations for unbelted passengers?

Anyway, it seems dumb that these parts are so hard to get now. I'll try to spend some time recreating the scan in CAD, both to practice my surface modeling skills and also to try to make it as enticing as possible for composite manufacturers to start making replicas of these parts.

I'm thinking that with an accurate CAD model, anyone can CNC route the shape out of something like pink insulation foam board and then pull a mold. Maybe bigjae46 or Karbonius or Mile End will want to get in on this? Would love to see a quality replica of this parts available in the future.


Also weighed the part out of curiosity. Came in at 1959 g. Not bad at all! I honestly doubt a CF version could be made lighter, but being able to buy something is definitely worth compromising a few hundred grams for.

[0-60motorsports]

Thats awesome you found a NOS one. I tried to get one from BMW direct and they dont even have the beige one in stock. This is because i have done mine in alcantara and i want to revert back to stock fabric....So thought i could sell the alcantara one locally and......

[Obioban]

The euro wagon/sedan pillar covers are also much tighter to
the chassis. Running euro pillars gave me notably better sight lines (A pillars) and more shoulder room (b pillars).

never checked the coupe’s Bs, but sadly there was no similar gains to be had for the As.

[bigjae46]

I'm thinking that with an accurate CAD model, anyone can CNC route the shape out of something like pink insulation foam board and then pull a mold. Maybe bigjae46 or Karbonius or Mile End will want to get in on this? Would love to see a quality replica of this parts available in the future.


Also weighed the part out of curiosity. Came in at 1959 g. Not bad at all! I honestly doubt a CF version could be made lighter, but being able to buy something is definitely worth compromising a few hundred grams for.

Interesting. I'd have to use a CNC service. Is it possible to use the CAD model and then the CNC service make it in 3-4 parts that I can bond together? A carbon part should be about 33% lighter. You'd have to figure out what areas need to maintain the original part thickness and add some layers along those edges - which would add weight.

[heinzboehmer]

The euro wagon/sedan pillar covers are also much tighter to
the chassis. Running euro pillars gave me notably better sight lines (A pillars) and more shoulder room (b pillars).

never checked the coupe’s Bs, but sadly there was no similar gains to be had for the As.

Looks like the same part numbers for all the coupe pillars between euro and USDM, so unfortunately no upgrades to be had.

Checked the E82 as well, since the giant A pillars on it are one of my biggest complaints, but again, no difference.

Interesting. I'd have to use a CNC service. Is it possible to use the CAD model and then the CNC service make it in 3-4 parts that I can bond together?

For sure.

But honestly, I think finding someone local with a CNC router and routing it out of pink insulation foam is gonna be way easier and way, way cheaper. That's how most of the RC plane people build their stuff, so maybe someone in that space can help out.

Random video pick, but jump to 4:20 for an example: https://www.youtube.com/watch?v=o6FMjOl0TRA

A carbon part should be about 33% lighter. You'd have to figure out what areas need to maintain the original part thickness and add some layers along those edges - which would add weight.

How did you get to the 33% lighter figure? Scan measures in roughly at 1.5 m2 for surface area of the part. A layup with 4 (to make the part thickness ~1mm) 210g 2x2 3k layers would weigh ~1260 g dry. Leaves very little margin for the weight of the resin + fabric, unless 4 layers is way overkill.

Also, the part is made opposite to what you're describing (and what I expected originally). The thickness is ~5 mm throughout most of the part (sans fabric), but the edges are "crimped" down to ~1 mm to fit under the other trims in the interior. I'm guessing the increased thickness in the middle is for either stiffness or NVH. If the carbon part is stiff enough, it could likely be made at 1 mm thickness throughout. NVH is easy to address with the "recycled jeans" insulation (51488229733 + 51488229734) that you can get from BMW.

[bavarian3]

Few updates:

Update 3:

1. I managed to get my hands on some unobtainium:

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20260504_200205.jpg","data-attachmentid":35356}[/ATTCH]
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20260504_212759.jpg","data-attachmentid":35457}[/ATTCH]
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"20260504_214123.jpg","data-attachmentid":35458}[/ATTCH]
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"original_9b24949e-b155-46de-89f5-6d3277b4ce90_20260504_214139.jpg","data-attachmentid":35459}[/ATTCH]

A never installed, NOS, 2021 production date euro slicktop headliner, courtesy of ridebikes. Incredible!

Gonna be kept in storage until I get the carbon roof project going, but I did do one thing before putting it away:

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"Screenshot 2026-05-05 at 1.11.57\u202fAM.png","data-attachmentid":35430}[/ATTCH]

Can check out the scan here, if you're curious: https://s.digital3dcloud.com/space/f...b-56687ab66f9f

Interesting to see how different the euro part is to the USDM one, especially from the back. Here's an internet picture of the USDM headliner, for reference:

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"IMG_5909.jpg","data-attachmentid":35461}[/ATTCH]

This makes me think that the foam and aluminum honeycomb structures are there for crash safety and not NVH, like I originally thought. Maybe it has to do with the extra US regulations for unbelted passengers?

Anyway, it seems dumb that these parts are so hard to get now. I'll try to spend some time recreating the scan in CAD, both to practice my surface modeling skills and also to try to make it as enticing as possible for composite manufacturers to start making replicas of these parts.

I'm thinking that with an accurate CAD model, anyone can CNC route the shape out of something like pink insulation foam board and then pull a mold. Maybe bigjae46 or Karbonius or Mile End will want to get in on this? Would love to see a quality replica of this parts available in the future.


Also weighed the part out of curiosity. Came in at 1959 g. Not bad at all! I honestly doubt a CF version could be made lighter, but being able to buy something is definitely worth compromising a few hundred grams for.

I was hoping you picked this up! I almost bought it but shrugged it off after he upped the price behind the scenes.

These definitely need to be replicated, even just as an non-upholstered blank. Though I've removed 3 of these recently and there does needs to be some flexibility in the part for R&R. Also, unless the windshield is pulled, it's a pain getting it through the door.

[heinzboehmer]

I was hoping you picked this up! I almost bought it but shrugged it off after he upped the price behind the scenes.

These definitely need to be replicated, even just as an non-upholstered blank. Though I've removed 3 of these recently and there does needs to be some flexibility in the part for R&R. Also, unless the windshield is pulled, it's a pain getting it through the door.

Yeah, it was silly money, but what are you gonna do. Seller got a higher offer than mine, came back to say that I was still first in line and that if I could match the offer, I could have it. Free market and all that. I blame BMW for not making these anymore more than anyone else

Also, I'm hoping the ridiculous price and non-existent availability will be a net positive for the community. Would have never thought to try and recreate this part had either of those not been true.

Anyway, appreciate the insight on the R&R! I've only ever done this job on a wagon, which is cheating cause the whole rear of the car gets out of your way. I know this is tough to quantify, but how flexible would you say it needs to be? Needs to shrink to 95% of its width? 80%? 50%?

Could you conceivably get it into the car with zero flex if you remove the door and seat?

(I know that last bit sounds kinda insane, but both of those components are surprisingly easy to pull on this chassis)