Black & Tan 332iT

[Arclitgold]

Wow this car keeps getting better and better! Nice work and keep it up!

houses are endless sources of… well lots of good and bad! Haha

[Bry5on]

Alright, I had a few free hours this morning and there was an open lift, so here we go!

How it started:


A few minutes later:


And another 30 minutes after that, we're all buttoned up again and ready for a test drive:


This is the F80 driveshaft that EthanolTurbo had modified with e46 M3 flex disc and CV joints. It is exactly 5mm shorter than a factory M3 driveshaft. Because it's shorter, I did not have to unbolt or drop the diff or subframe to install it, as you can see above. This is a tradeoff, as there will be less spline engagement with the driveshaft and CV joint. I think 2-3mm shorter than stock would be the sweet spot if you're not using the telescoping F80 version of the shaft (which is a better solution overall, in my opinion). Install was easy, just like any other driveshaft, only made difficult by the shitty supersprint header joint.

We measured before that this shaft is 80mm OD, versus the 75mm max OD stock shaft, so the math says that this carbon shaft should be much stiffer (bigger diameter, 50% stiffer material, likely also thicker wall) than the original and also bring in some of the inherent damping that carbon weaves have that steel does not. It's also one piece, although I don't think this is likely to have any real noticeable effect from the seat. We measured that it's 3.5lb lighter than the steel part, which I also don't think will be too seat of the pants noticeable, because inertially these math out to be very similar due to the larger OD of the carbon shaft.

Because this shaft is larger OD, it's a very tight fit. This is only suitable for cars with non-raised, solid subframe bushings. My car has *non-raised* & solid subframe bushings with reinforcement plates (4-5mm thick, which helps gain clearance) and I had about 8mm clearance to the transmission tunnel. Any displacement of the subframe/diff under acceleration or due to adding subframe raising solid bushings is likely to put you at risk of hitting the transmission tunnel and disintegrating your driveshaft. Consider this fair warning if you choose to go carbon, and I cannot stress this enough. Carbon does not fail subtly or slowly.

https://youtu.be/umdLZ_PUL_w

Good news, I did not have to make any clearance to my unmodified exhaust heat shield.

So what's the verdict? My initial thoughts say a very minor positive difference versus steel.

First of all, since I'm in San Diego it's easy for me to make a quick trip to Mexico where I tested the car up to 120mph (with stock gearing) and had absolutely no noticeable vibration. I'm sensitive to vibration. Sort of OCD about it. In fact, I'd say that the car is ever so slightly quieter at speed. I was expecting this as it's a common noted difference, so there may be a bit of placebo here.

When I initially took the car for a drive, I was pretty hopeful because I couldn't detect any semblance of the m-clunk. This changed once the car had warmed up. I'd say this was a mild improvement to the clunk (more of a thud now in my car), definitely less of an improvement than the rear end bracing made (my touring cabin X-brace and subframe-v-brace). Any improvement here is welcome, but it's not a magic bullet. Shift & shifter quality is largely the same, just with slightly less of the thud on a hard 1-2 shift.

There is also an improvement during clutch take-up, it just feels smoother and a bit more direct - in the direction of, but not equivalent to, a Porsche. This is maybe the most detectable and biggest difference.

There is no perceptible increase in the car accelerating quicker or revving faster that I can tell. Note that the math also generally agrees with this.

On just one occasion, it did seem that I was able to excite some natural frequency somewhere around 40-50mph under WOT second gear acceleration after a 1-2 shift. It felt similar to a failing CSB, but I wasn't able to reproduce this, so it could have been coming from the road, as I was on a highway onramp in a landfill area.

So overall I'd say this is mostly a smoothness, directness and NVH improvement, in that order. All effects are relatively minor but if you're OCD about NVH and needed a driveshaft balance like me anyway, I'd say go for it. It's an improvement. If you don't need a driveshaft, maybe wait until your next 'while I'm in there' opportunity. If you're debating whether to do this or a chassis stiffening mod first, *definitely* do the chassis stiffening mods first, you'll feel those a lot more.

Hope that's helpful!

[heinzboehmer]

Still struggling for blocks of time - setting up the house is taking priority.

Man, I feel that. It's no fun.

X brace looks great in black though.

[Bry5on]

Still struggling for blocks of time - setting up the house is taking priority.

But I did get a chance to powder coat the rear x-brace, and while it was out I had to drive the car without it for a week, on my regular commute, so I’ve got some reverse observations.
1) the car is smoother on hard impacts without the brace but there’s more after-bump ‘noise’ that’s not generated by the road. Sort of like a ripple after effect.
2) steering precision with the brace is definitely better
3) the m-clunk came right back on removal and turned back to an m-thud on reinstallation. I’m convinced that the clunk is exacerbated by the flexy trunk floor. Constraining it with the combo of the rear x-brace and the subframe-v-brace does the trick, and I think you need both to net the results. This also supports my theory that bracing to the center isofix attach point is necessary.



Next up we’ve got to see if the carbon driveshaft from EthanolTurbo eliminates the rest of the clunk because of the damping effect that carbon has.

[Bry5on]

Print a fixture! Then a boring bar on the lathe/mill and good to go.

Always coming at me with the logic. Of course!

[heinzboehmer]

3) I opened up the strut clamp bore on the new part and probably shouldn't have. The holes came in a little ovaled, and now I think I'll need to find an actual solution to this problem to make them round. Aluminum tape will do for shimming the oversized hole, but I'll need a way to fixture it straight which could be challenging.

Print a fixture! Then a boring bar on the lathe/mill and good to go.

[Bry5on]

Okay, good news and bad news. Good news is that I ordered the other side printed knuckle and it's already on its way over the pacific to me.

Bad news unfortunately is more than the good news:
1) I neglected to realize that I couldn't simply mirror the ABS mounting orientation, as the sensor is not centered through its bore. I'll need to come up with a solution for this, have some ideas, but it's an annoying problem to have.
2) The large hand reamers showed up and I reamed the bores for the LCA and tie rod inserts. The bores *did not* clean up with the reamers. So it looks like my caliper measurements were wrong and the bores did not come in undersized like I thought. We'll see if the next batch is the same. Currently debating whether I order some adjustable hand reamers, or chance it and use a press-fit adhesive to take up the slack.
3) I opened up the strut clamp bore on the new part and probably shouldn't have. The holes came in a little ovaled, and now I think I'll need to find an actual solution to this problem to make them round. Aluminum tape will do for shimming the oversized hole, but I'll need a way to fixture it straight which could be challenging.



I also got to an oil change this weekend. Well, turns out that the preventative timesert that I did in my oil pan drain plug hole didn't swage in properly, or I used the wrong grip length. It was pulling out instead of the fastener.

I wasn't prepared to deal with that problem, so I change the oil from the top by sucking it from the dipstick tube. And well I use the CSL dipstick tube, so that meant removing the Slon brace and the front half of the intake. Normally not a big deal, but the vacuum port on my karbonius airbox had debonded a while back, and I knew I'd have to fix this next time the airbox was off, or I wouldn't be able to reconnect that vacuum tube.



So, some epoxy later and that was fixed. And that 15 minute oil change was done 3.5 hours later.



I also learned something very interesting. The e46 cabrio uses different seat mount points. Mount points that are 40mm narrower on the outside vs the non-cab. *checks math* - why yes, that's the same dimension as the e90/f80/etc seats.. so you're telling me there's a way to run the lovely vented/heated M3cs seats in the e46 if we use cabrio seat mounts? I'm intrigued.



And one more thing. Thanks to EthanolTurbo I've got his F80-e46 M3 modified carbon driveshaft on the bench to measure and test. More detailed numbers here: https://nam3forum.com/forums/forum/m...945#post318945

[Bry5on]

This is such an incredible project! 2005-me would have been blown away to imagine this being in the realms of possibility for an individual to achieve!

Seriously, that makes two of us. Very cool to have been able to use both generative design and 3D printing for a personal project! The last 3D printing project I was involved with was very much more complex than this, it’s pretty incredible what you can do nowadays.

[karter16]

This is such an incredible project! 2005-me would have been blown away to imagine this being in the realms of possibility for an individual to achieve!

[Bry5on]

First Article has arrived. Overall it looks pretty good, feels very beefy, and they didn't take too much off anywhere for cleanup of support material. Even the M6 threads printed out reasonably well and just needed cleanup with a tap - pretty wild. All hole bores came in under by ~0.2mm, so I'll open up a couple of the clearance holes before printing the next part, but other than that, I think this is ready for prime time.

Next up, have to machine the LCA and tie rod inserts, heat treat/quench the part, open up the hub locating bore, finish the bores of the LCA and tie rod mating interference fits, then this thing is ready for install. Wild!

Thanks to all the folks running the mullet tune, the proceeds have made this project possible.

[Obioban]

Need to get a scan of the CSL's in the mix.

[Bry5on]

Oh, clever!

Kinda blown away by the findings. They're far more different than I though they were.

Honestly, same reaction I had. Almost didn’t believe my eyes as it’s clearly a derivative but a totally different forging.

First principles has the on center steering ratio at 16.33:1 for an M3 CSL/ZCP and 15.4:1 for my knuckle. Recall that the 992 ST is 15:1 in center, but 13.5:1 after accounting for wheelbase differences. So even with the ratio shorter than the non-m, we’re still a ways off the sports car.

[heinzboehmer]

Oh, clever!

Kinda blown away by the findings. They're far more different than I though they were.

[Bry5on]

I lined them up on the mounting bosses for the heat shield as I believe that’s a shared part number. Lots of geometry tweaks, ones I’ve noted (M3):
- Caster (increase)
- Trail (increase)
- Inner tire clearance (slight increase from moving strut inboard)
- Ackerman (decrease)
- Scrub (increase)
- Bump steer (hard to say direction, but probably decrease)
- Caliper clocking, radial- and back-spacing

[heinzboehmer]

Huh, that's surprising. Static camber and caster (and toe?) look different too?

I would trust the geometry of the pickup points for the LCA, tie rod, strut and caliper brackets in the scan. Not sure I'd trust the relation between the hub and the aforementioned features, though. The heat shield was hard to wrap the scan around.

What happens if you line the scans up on the LCA/caliper bracket mounting points? I would think those are the same between the M and non-M knuckles. Almost looks like the non-M tie rod pickup point would end up higher than the M one, resulting in a slight change in effective LCA to tie rod distance.