heinzboehmer's 2002 Topaz 6MT Coupe

[smee123]

Surface prep is king with 3m structural adhesive just like the importance on the loctite and their activators. Maybe trivial on an oil pan drain time sert l, but on anything that experiences any pulling loads or any inherent vibrations, I cant stress it enough!!

[heinzboehmer]

Maybe I missed it...any reason you chose 07333 vs 08115 (panel bond)?

Based on 3Ms own recommendation

07333 is for structural stuff, 08115 is for non structural body panels:

3M Panel Bonding Adhesive Designed to meet specific strength requirements for outer
sheet metal panel replacement; panel bonding adhesive is
typically used in conjunction with welding, rivets or hem
flange joints. Panel bonding adhesives do not offer the same
level of impact resistance as impact resistant structural
adhesives and should not be used for structural repairs unless
recommended by the specific automotive manufacturer.

3M Impact Resistant Structural Adhesive
Designed to meet specific strength requirements for parts
such as frame rails, strut towers, sills, pillars and other
members where impact resistance is important. This type of
adhesive possesses a much greater ability than traditional
bonding adhesives to absorb and manage energy under a
variety of forces, especially peel and cleavage stresses in
extreme temperature conditions. Typically
impact resistant structural adhesive is used in conjunction
with rivets, spot welds or mechanical fasteners.

Document where that quote came from is attached.

[bigjae46]

Oooohhhh! Now I understand how it fits. I've looked at the part and never understood how it would mount. lol

Maybe I missed it...any reason you chose 07333 vs 08115 (panel bond)?

[heinzboehmer]

Bonding time!

Started by clearing everything I could out of my way. This essentially amounted to airbox, blower motor, blower motor housing, engine beauty cover, wiper linkage (just moved that out of the way) and windshield cowl. I also covered up any openings that metal shavings could fall into:



Removing the blower motor absolutely sucked. It's like there was no effort dedicated to serviceability of that assembly when it was being designed. I did do it all with the windshield mount roughly in place, just to make sure that it was still doable. Fortunately, it didn't get in the way at all.

Gonna do my future self a favor and document the best way I found to remove the blower motor:

1. Remove the front cover. One screw up top and two clips at the bottom. I still don't know how BMW expects you to get that piece past the firewall, but with enough swearing and bending, it'll come out.



2. Remove the passenger side cover. Undo the three screws holding it in (circled) and remove the two linkages attached to it. Take note of how the linkage for the secondary flap is clocked so that it goes back together in the same way.



3. Unhook the blower motor (no need to undo the four screws of the mount) and wiggle it out through the passenger side. Be careful to not catch the vanes on the front cover clips and damage them. Also, the engine harness has to be moved out of the way for it to clear.



Anyway, back to prep.

Started by test fitting the aluminum piece for the final time and then tracing its outline on the chassis:



Then, time to sand. Started manually, but very quickly gave up. Dremel made fairly quick work of it:



I followed that up by sanding with 220 grit, then a bunch of acetone wipes to get rid of all debris and finally an IPA wipe. Adhesive next.

And then this happened:



Bad picture, but one side of the adhesive cartridge blew out the back and leaked everything that was in there.

Admittedly, this was entirely my fault. Turns out the applicator I have does not fit the 07333 cartridge. I didn't realize this until today, so I decided to fix the issue with some zip ties. It worked great until it caused one of the cartridge pistons to spin inside the cylinder and cause the mess above.

Lesson learned. Next time I need to jerry rig an applicator, I'll throw some sockets into the cartridge cylinders to spread the load.

Replacement adhesive (and appropriate applicator) ordered. Will give this another shot in a few days....

[Bry5on]

That’s weird… m3 strut brace fit under my M3 wagon hood without any cutting/trimming 🤔

Mine cleared statically but contacted (just barely) dynamically. Good times!

[heinzboehmer]

Wow there really is a lot more clearance under the M3 hood. I had to cut my non-m hood a little just to clear the factory strut brace.

Mask off the area well before sanding, it’ll be worth it. And don’t skimp on adhesive - wet each surface first then S shaped or fishbone shaped beads to allow air to flow out while you install will give you the best chance of a good bond with fewest air pockets. I always prep with acetone then one directional IPA wipes right before bonding as well.

Good luck!

Thanks! Will do that.

Airbox is just loosely set in place in those pictures. Both that and the blower motor are coming out for the install. Gotta make sure I have the most access possible.

Also got myself a cheapo space heater that I'll throw in there to help with the curing.

[Obioban]

Wow there really is a lot more clearance under the M3 hood. I had to cut my non-m hood a little just to clear the factory strut brace.

Mask off the area well before sanding, it’ll be worth it. And don’t skimp on adhesive - wet each surface first then S shaped or fishbone shaped beads to allow air to flow out while you install will give you the best chance of a good bond with fewest air pockets. I always prep with acetone then one directional IPA wipes right before bonding as well.

Good luck!

That’s weird… m3 strut brace fit under my M3 wagon hood without any cutting/trimming 🤔

[Bry5on]

Wow there really is a lot more clearance under the M3 hood. I had to cut my non-m hood a little just to clear the factory strut brace.

Mask off the area well before sanding, it’ll be worth it. And don’t skimp on adhesive - wet each surface first then S shaped or fishbone shaped beads to allow air to flow out while you install will give you the best chance of a good bond with fewest air pockets. I always prep with acetone then one directional IPA wipes right before bonding as well.

Good luck!

[heinzboehmer]

Timeserts installed and fitment of hardware validated with 3D printed fasteners:




Looking good!

I need to temporarily swap back to the stock airbox this week for, uh, no reason. I'll likely bond this in when everything is out.

Okay, I lied a bit with this post. Timeserts were dry fitted, not actually installed. Couple notes from the real install:

1. By complete coincidence, smee123 made me aware of the fact that Loctite threadlocker is only designed to work on what they call "active" metals. Important thing to know is that if you're using threadlocker on aluminum (or other "inactive" metals), you should also be using their activator, so I did.
2. The clearances on the back hole are tight. I designed it so that a bottoming tap would be needed to cut the thread for the insert. The tap in the timesert kit seems to be a custom diameter, but an M10x1.25 tap is very close and cuts those last few threads just fine.

Piece is actually ready for install now, will be doing the bonding tomorrow. Quick picture of all the hardware needed:



I also modeled some wedges to hold the piece against the chassis while the adhesive cures. Currently being printed:



Moving on to the the strut tower brackets...

One concern I have is that the stock pieces will be spaced up slightly when all is said and done. How much displacement depends on the amount of material I machine off. If I use the 3.75 mm value, that means the brackets and bar will end up 1 mm taller. Additionally, the replacement studs will stick up 2.25 mm more than stock, so max height change will be +3.25 mm.

This is a small amount, but I still wanted to be sure that it wouldn't cause an issue. So I grabbed some modeling clay and squished it in between the hood and potential contact points:

Test setups:




Results:





Honestly, wow. That's way, way more clearance than I was expecting. Not even gonna bother measuring, my stuff will fit just fine

[heinzboehmer]

Wow, just seeing all this wonderfull stuff, great work!

I am very interested in the CSL ducting, what a great idea. Would there be the possibility of having one that let's some air past for brake cooling?
Maybe I could just get this one and cut out a small section in for that purpose.

I would imagine the IAT would see lower temps as a result, very cool. The strut brace project is cool as hell too, I may have to get into this stuff.

You need to talk to Bry5on about the duct! No need to integrate brake cooling in the duct if you also install his Porsche-style brake cooling scoops.

Let me know if you're ever over here! Welcome to drive the car and feel all the bracing for yourself.

[Cubieman]

Wow, just seeing all this wonderfull stuff, great work!

I am very interested in the CSL ducting, what a great idea. Would there be the possibility of having one that let's some air past for brake cooling?
Maybe I could just get this one and cut out a small section in for that purpose.

I would imagine the IAT would see lower temps as a result, very cool. The strut brace project is cool as hell too, I may have to get into this stuff.

[heinzboehmer]

Where do the E86 strut bars boit to? One of the existing press in studs?

I still have to figure out where/how I want those to land, so I haven't modeled the studs in yet. But they'll go somewhere in the protruding yellow surface. I printed up a prototype, so I'll do a test fit and post up some pictures in the coming days.

You can eliminate the S shaped wall because you’ve otherwise boxed the shape in by attaching it to the aluminum strut brace. Pretty sure that little wall will not have much contribution to strength and you can avoid weakening the material by eliminating welds. You might wind up just redesigning strut tower bases entirely when this is said and done though

Oh good call! Completely overlooked the weakening of the material. Will incorporate that suggestion into the design.

And yes, I'm doing my best to keep the stock look, but there is a decent chance that I abandon that entirely and just redesign the entire thing.

If you’re doing new bases, you could also add fastener locations on the fender side for future gusseting to the corners of the windshield too. You know, for a future project..

I do love me some scope creep!

[Bry5on]

You can eliminate the S shaped wall because you’ve otherwise boxed the shape in by attaching it to the aluminum strut brace. Pretty sure that little wall will not have much contribution to strength and you can avoid weakening the material by eliminating welds. You might wind up just redesigning strut tower bases entirely when this is said and done though

If you’re doing new bases, you could also add fastener locations on the fender side for future gusseting to the corners of the windshield too. You know, for a future project..

[bigjae46]

Where do the E86 strut bars boit to? One of the existing press in studs?

[heinzboehmer]

Some updates.

First, my CD53 is back from the UK (with nothing changed), so I tested that in my car. Audio sounds as good as it did with the junkyard radio! This leads me to believe that the HK amp was the culprit after all. So, my PSA for the day is: service your HK amp!

And now the bigger/longer update. 3D scanner got put to use and I started designing the replacement strut bar brackets for the E86 braces. Here's both stock brackets scanned:



Before I started doing anything, I wanted to verify that the profiles of these are indeed symmetric (brackets themselves are not symmetric, passenger side has some extra clearance for the positive terminal):



Nice.

With that out of the way, I moved onto the actual design. As a reminder, my plan is to machine down the bosses on the stock brackets and sandwich them in between my brackets and the stock bar.

The only real constraint (besides the obvious spatial ones) is that I can't machine the brackets down too much. The passenger side one gets fairly thin where there's clearance for the positive terminal:



My plan is to fully machine down the bosses and just barely skim the rest of the surface to get it fairly flat. Quick measurements say that I'll be taking about 3.75 mm of material off, but I won't know for sure how much it ends up being until these are on the mill. I'll start with the hard one (passenger) and then copy whatever I do over to the other one. Hopefully I can get down to the shop soon.

Anyway, here's my initial approach for the bracket. There's a decent chunk of stuff to work around in these areas, so the funky geometry is a result of that:






These are designed to be laser cut, bent and welded. M8 press in studs will be used in my bracket and I'll drill the threads of the stock brackets out so that the new studs can pass through. M10 stud for the E86 brace is not shown, but it'll go somewhere in the protruding yellow section. I'll have to fit a prototype up in the car to see if that section is long enough, it might not be as is.

I still don't know if this current design is manufacturable, though. Some of the bends look like they'll be hard to pull off. Fortunately, I should be able to extend any problematic walls and then cut the piece down myself post bending.

The other concern I have is that the stock brackets don't leave a lot of room for gusseting the section with studs to the flat section that goes on the strut tower. I did my best with that S shaped wall, but there's no room to do much more than that. I think it should be fine, mostly because of these reasons:

1. Plan is to get these brackets made out of 4.75 mm thick 304 SS, so they should be tanks.
2. The stock brackets will help with the stiffness of the entire assembly. Remember I'm really only machining down the bosses, so they should be as strong in bending as they are now.

And that's about it for now on these. I really can't do much more until I get myself in the shop and machine the brackets.