Black & Tan 332iT

[Bry5on]

Okay a little practice and I'm getting better. Once you start adding all the keepout spaces for bolts, wrenches, ratchets, AND sensor and install direction, control arms, tie rods... you can see how BMW arrived at the e60 'bowl' shape design. I'm a few simulations in now and they're all coming in around 2-3kg with 4-7x safety factors in printed/machined aluminum and 5-15x safety factors in Ti. I used some pretty hefty loads, like 2G in braking and 1.6G cornering to build the model. I'm sure there's lots of mass optimization to be had here, but since I'm really trying to optimize for stiffness without invalidating strength, Ti probably won't be much of a benefit at all over Al, practically speaking. I'll keep you all posted.


Example aluminum solves

[Bry5on]

Okay, I couldn't help myself. I'm going to try the built in generative design tool in Fusion. Looks like the e60 hub will package within the e46 available space..

[Bry5on]

Made some progress modeling bank 2:


Interesting to note that as George Hill pointed out - the US bank 2 header crosses over to the *passenger* side of the car, where the euro bank 2 header stays on the *driver* side of the car. Odd!

Edit, some details:
Tube is 40mm OD, 1.5mm wall (37mm ID) and all bends in bank 2 are 40mm radius
Runner length is somewhere around 320mm when you include the length of the exhaust port
A post-step size of a 5/8" OD, .065" wall should work well with the stock pipes
I just purchased an exhaust textbook so that I don't royally screw this up.

[Bry5on]

Thanks to a fellow member here (thank you!), today I got a good scan of a front suspension knuckle for a future project. Figured I'd make it available here for anyone who wants to use it for design purposes: https://s.digital3dcloud.com/space/f...lang=en&loop=1

[Bry5on]

Progress. What's next.....

[Bry5on]

Another couple hours, trying a different technique that's easier to model but basically has to be 3D printed instead of mandrel bent. I'll probably end up doing both techniques in the end, the easier to model for mockup and the easier to manufacture for final version. Bank 2 on the left in the photo is equal length, again just practice. You can see I'm working to get the hang of keeping fastener and tool clearance for installation.

[davidinnyc]

It's all those throttle blip downshifts with the smooth tune

I need this soon!


Sent from my iPhone using Tapatalk

[Bry5on]

It’s all those throttle blip downshifts with the smooth tune

[0-60motorsports]

...or Bryson sends it harder than anyone else on the boards!

lol maybe

[davidinnyc]

The plastic probably got brittle by age and heat.

...or Bryson sends it harder than anyone else on the boards!

[Bry5on]

First couple hours in Fusion 360 logged. Rough but it's a start.

[0-60motorsports]

The plastic probably got brittle by age and heat.

[Bry5on]

I got to meet George Hill this weekend which was super fun, and we scanned about half of the things we wanted to (my fault, I was short on time). But we did get a good scan of the aluminum shear plate and a couple good scans of an s54 in an empty engine bay to get header placement and clearances in the case that I can come up with something clever in the future for an actual equal length and stepped header. Also, if anyone has a loose front control arm with bushing and a loose front knuckle in the Bay Area, let me know. Most ideal if you also have a front strut to scan with the knuckle. Any condition as long as they're not bent, just need to get good scans.

And on my way home last night, I went for a couple repeated downshifts into my favorite local challenging corner and my final downshift into second didn't respond to my foot. I was left to drive the last mile home with about 2% max throttle and the dreaded EML, DSC and BRAKE lights all lit up in front of me. Well today I started digging around and after measuring the TPS sensors decided to just actuate the throttle by hand to rule out an interference. I felt an odd step as I swept through the throttle opening, so I poked the flashlight down into the engine bay and found this, the arm between the actuator and the throttle bodies had cracked and popped off. Pretty cool that the car is fault tolerant of losing the throttle bodies entirely, as I was able to drive home using just the ICV as throttle (this is how the s54 normal operates at light throttle anyway). Clever engineers! New arm should be here in a week or so.





And while I was in there I replaced the Phillips fasteners with hex thanks to heinzboehmer

[0-60motorsports]

I think that F80 M3 is a nice solution. Thanks for posting that info.

[Bry5on]

So I took another e46 friend's advice while I was under the car to swap out some parts.

First, I replaced the header exhaust clamps with a factory BMW part, because a bracket that is braced on both top and bottom of the pipes should be way stiffer than one that's just braced on the bottom. I used PNs 18307850435 and 18307850436 from the F80 M3 which has similar diameter pipes to the SSv1s. Here's what that looks like:





Then I took some measurements of the frequency response of the exhaust while smacking it. I did this in a not-great-but-probably-fine way by holding the iPhone to the exhaust and smacking it locally with my hand in the horizontal direction right next to where the phone was. I used the iPhone's internal accelerometer which only samples up to 50Hz. This produced some plots of oscillation frequencies at various points.

The muffler, as expected a very low frequency under 10Hz, this just is what it is, too low to damp:


The resonator, about 25Hz:


The cat(s), about 20Hz and just above 30Hz:

Then I decided that while I was double-bracketing things, I'd escalate the situation by doubling up the rear strap. This was pretty difficult to get in there, just in front of the cats, but what's done is done. For science.



Then I repeated the not-great-but-probably-fine test to see if there was a difference. Not much, and here are the plots:




I think that if there were another gain to be had, it would be by stiffening up the brace to the transmission and also attaching the brace to both pipes. There's not much room there so this will have to do.

And while we're on the topic of exhausts, I did another fun mini-experiment. I'd noticed that the rasp rpm seems to be lower on cold start than warm start, and I guessed that this was correlated with exhaust temperature. So I watched my EGT gauge while rasp happened and created a few data points:
- 2500rpm at 280*C EGT
- 2900rpm at 460*C EGT
- 3000rpm at 530*C EGT

The equation for the speed of sound is 331.3 * SQRT(1 + (Temp*C / 273.15) ). Let's plug in these temperature numbers and use the 280*C data point as our baseline. We get 471.5, 542.8 and 568.1 m/s. Well, 2900rpm is 16% higher than 2500rpm and 3000 is 20% higher. When you normalize the results of the speed of sound against that 280*C baseline, you see that 542.8 is 15% higher and 568.1 is 20% higher than 471.5 m/s. So, the rasp rpm increases as the temperature in the exhaust increases. I did some more math to see if I could simply correlate this with the difference in header lengths, but alas, nothing simple emerged in front of me. I thought at least it was a fun speed of sound experiment and validation.