Black & Tan 332iT

[kaiv]

Progress continues..


After that insert as practice, I turned to the real project. A ZHP bumper brake duct to CSL airbox inlet duct and accordion flex boot. First I masked off the area to get some good measurements and a 3D scan with the iPhone faceid lidar sensor, which gave me the local area and surfaces I needed to route a duct:


Then off to the 3D printer for a first iteration. I used the entire build height of the printer, and actually needed a few mm more, so I nipped the top 5mm off of the printed part of the duct. You'll see below why this didn't really matter after installing the TPU printed flexible accordion boot. This is actually version 2:



It helped having an extra CSL flap to get dimensions, as this is an odd shape:


And after adding some mounting points to V3, we're in business. This piece uses two factory mounting points to secure in place along with the bumper opening to locate itself in 3D space. From there, the CSL airbox is installed from the top just as it is on the factory CSL. The flexible TPU piece in between has a groove that locks into the CSL flap just like stock, and is flexible enough to snap/pop in place on install. It also has double walls to locate on the duct itself to make sure it stays positioned, even as the engine vibrates at high revs. So, here it is:



You can see here how the flexible boot fully encompasses the section of print I had to notch out:

Incredible work Bryson! Can't wait to get mine! 😄

[Bry5on]

More rainy day projects, I started working on a brake duct that'll be much much better than the one I removed to install the CSL intake duct. Here's a first draft in CAD, and tomorrow afternoon I should have the prototype all printed up.

https://www.youtube.com/watch?v=m5zYhd987Ds

[0-60motorsports]

More rainy day projects, I started working on a brake duct that'll be much much better than the one I removed to install the CSL intake duct. Here's a first draft in CAD, and tomorrow afternoon I should have the prototype all printed up.

https://www.youtube.com/watch?v=m5zYhd987Ds

Oh Will this fit cars with OE CSL intake setup and CSL bumper?

[Bry5on]

Oh Will this fit cars with OE CSL intake setup and CSL bumper?

This will fit all M3s, and will provide effective brake cooling for a car with a CSL bumper especially. It's also designed to clear 17" wheels and the highest possible wheel offsets that won't hit the strut. Bigger wheels will just have more clearance.

[0-60motorsports]

This will fit all M3s, and will provide effective brake cooling for a car with a CSL bumper especially. It's also designed to clear 17" wheels and the highest possible wheel offsets that won't hit the strut. Bigger wheels will just have more clearance.

Thats awesome! Looking forward to it. I would love to return brake cooling to my CSL Bumpered M3 again.

[Albino09]

Is this effectively an air scoop grabbing from the bottom of the wheel well? I can kind of make out the rough shape of the tire and the control arm but having trouble figuring out my xyz reference.

[Bry5on]

Is this effectively an air scoop grabbing from the bottom of the wheel well? I can kind of make out the rough shape of the tire and the control arm but having trouble figuring out my xyz reference.

Precisely. Test fit yielded a few tweaks for clearance at full lock. Otherwise it’s looking good.

[Bry5on]

Well today I was home sick with a cold, so in between meetings I installed v2 of the scoop duct and did some highly scientific testing. This version has some tweaks to make it print better, and to clear the tie rod boot and tie rod itself at full lock in either direction. In the process of this I also eliminated the shroud on top, which means this duct is now compatible with the OEM brake ducts (I tested the flow outlet location using the method I'll outline below).

First off, here's clearance at full lock in either direction. It's extremely close duct-duct in one direction, and duct-tie rod boot in the other direction. I wanted to maximize function, so I set these to be super close.
Full lock left (view from front of car looking back):

Full lock right (view from top down, showing the tightest clearance which is duct-duct):


Here's what it looks like when you're driving straight ahead, again from the front of the car looking back:

https://youtu.be/oP8onVb59pE

No problems there, everything looked good, so I moved on to validation testing. I tested two configurations: one where the air/water deflector attached to the pork chop is in place, and one where it was folded back, out of the way. I chose these two as the lower edge of that deflector and my scoop are both between 85-90mm off the ground, meaning there would be a good chance this deflector would prevent the duct from functioning.

The test setup was an electric leaf blower and some yarn telltales:




I did a round of testing with the wheel locked full left so I could witness the telltales, then repeated the two tests with the wheels straight ahead so I could see the telltale on the outer rim of the rotor (spoiler, it moved!) and through the wheel barrel/rotor. Here are the results:

https://youtu.be/8Zhji8t9YA8

So we learned that yes, the water/air deflector does prevent the duct from functioning correctly (at least the under-car scoop function), and we also learned that once that's out of the way it effectively moves an incredible amount of air through the rotors. I put a telltale on the outlet vein of the rotor, *away* from the highest pressure source, and the telltale moved when positioned at the vein, and also when I draped it over the 'Swiss cheese' holes in the CSL rotor. This was also confirmed by simply placing my hand outside of the spokes of the wheel and feeling the air rushing out (some of this was likely bypassing the duct I'm sure).

So following that testing, I trimmed the water/air deflector back on the inner edge to expose a nice clean air path to the duct.
Before:

After:


Next up will be some controlled speed/hill descent braking tests followed by IR temp sensor readings of the left and right rotors, as I didn't install a duct on the passenger side so I could get a proper A/B test. Stay tuned.

[YoitsTmac]

Very impressive. I like the thoroughness of your tests. Keep up the great work!

[Albino09]

I've always liked the look of the CSL rep bumper without an intake duct. These would nicely complement the deletion of the factory brake ducts.

[Bry5on]

I took my IR temp gun with me and drove the long way home for lunch. This allowed me to really put the brakes to their test on a 1,400ft descent. While on that descent, I made a point to hammer on the brakes (only in a straight line), drag them at WOT in second gear, downhill, accelerate, decelerate, etc while maintaining an average speed of around 40mph. Since the speeds are so low, I figured this would be a nice conservative test.

At the bottom of the hill, I turned off and drove for 1/2 mile or so at <15mph, then parked the car without using the brakes much. I recorded max temps of the rotor somewhere between 750-800F (very hot, visibly blue), then waited 6 minutes for the temps in the rotors to saturate. After saturation was leveled off, I measured 575F for the left rotor (the one with the scoop) and 600F for the right rotor (the one with the factory duct). I went back and forth about 10 times in that six minute period and the 25F temp delta was consistent for the duration.

I then drove back up the hill at about 30mph (off the brakes) for 4.5 minutes, pulled off and took another temperature measurement. The left rotor (scoop) had settled down to 310F and the right rotor (factory duct) had settled down to 325F.

I then turned off the datalog and drove leisurely ten minutes home under 25mph the whole way. Rotors recorded 210F +/-3 degrees or so once I pulled into the garage, and I couldn't really discern a difference between them at that point.

Datalog here, if you'd like to verify just how much I was on the brakes (positive longitudinal G is braking in my logs): https://datazap.me/u/bry5on/brake-sc...g?log=0&data=4

So it appears at first test that this scoop duct is an improvement over the factory design, even after eliminating the factory duct that would otherwise feed it. Also, the duct next to the brake shield didn't melt at all, surprisingly.

[Bry5on]

Alright, the passenger scoop ducts printed successfully so I installed those and performed a couple additional tests to see how they perform with the factory brake ducting in place.



First, the design clears the headlight sensor as expected, so we're all good there.



Here are a couple shots of the clearance to 17x9 et46 wheels at full lock. This is the smallest wheel and highest offset barrel that will fit on an e46 M3, so every other wheel and tire setup will clear these ducts:



Lastly, and most importantly, I repeated the leaf blower testing in two conditions: One through the factory duct and one from underneath the car as designed.

The test through the factory brake duct was enlightening, especially because this is the designed behavior of the Vorshlag duct that's already on the market. The air flows basically right into the scoop via the factory duct (perfect), but it hits a brick wall with little flow guidance. As a result, what appeared to be at least 50% of the air flows downward and back under the car. I have no reason to believe this would be different when using the factory ducts to the Vorshlag scoops - if you're using those and you're reading this, you should probably trim the water/air deflectors at the bottom of the pork chops to pick up some clean air from under the car. You can see below how the scoop manages the flow of the air underneath the car really well, in contrast.

The tell tales tell the tale here. Air coming through the factory duct, blowing every which way:


And air coming from underneath the car, a nice organized flow:


Very pleased with how these came out! Hopefully the data here is helpful.

[ARCHBID]

Well it was rainy all day today, so that means house and car work. The 6001 bearing at the bottom of the pinion shaft didn't feel so great, so I finished off the rack rebuild other than replacing this bearing (which arrives this week). I didn't bother replacing the PTFE seals as I don't have tapered tools to stretch/install them properly. Yet another concession that I hope I don't regret down the road..





I also got to painting the ground control lower control arm replacements. I haven't been able to get camber in spec on either side (maxing under 1.6 degrees on both sides), and I figured I'd try a set of arms with a ball joint a la CSL. The ground control arms are a nice shade of red, but I'm not exactly jazzed about having some red arms showing from underneath my car as folks follow me. It just screams 90's Honda Civic to me. I also found it a bit odd that the two arms are using what appear to be different brand ball joints.

Where did you buy the rebuild kit?

[Bry5on]

Where did you buy the rebuild kit?

I think it was ECS? It was made by Gates

[Bry5on]

Okay, let's get rid of some more NVH. Vibration this time.

I pretty much got the SS headers and section 1 to idle as well as stock by strapping the two pipes together, but after more driving I still wasn't satisfied with what I was perceiving to be some persistent exhaust natural frequency resonances. There were three frequencies that were bugging me; one at very near, but not quite, idle speed, one at about 1700rpm and one at about 3300rpm. I figured these were associated with the first, second and third natural frequency modes of the exhaust.


So let's do something about it to arrest those modes. Well, what's the best way to neutralize them? To shorten the unsuspended length of the exhaust and shift the frequency modes much higher, way up or out of the excitement of the RPM band completely. You can see using the above math that the natural frequency scales to 1/L^2, where L is the length of the unsuspended exhaust in this case. So let's use a trick from several other non-s54 BMWs used before, during and after this generation. We're going to make a bracket that ties the exhaust to the back of the transmission, using its existing but unused mounting bolts. Since the transmission and exhaust are both rigidly mounted to the engine, these parts already move together, and tying them together should not introduce any weird relative motion. And since the transmission is significantly further toward the rear of the car than the headers, this will effectively reduce the length of the exhaust left to vibrate 'freely' (note that the exhaust hangers don't do much to arrest natural frequency induced oscillations, that's what those non-m e46 cylindrical dampers do). The one thing to keep in mind is that the exhaust grows as it heats up, so the flexural orientation of the mount, and giving it enough length to bend elastically, is important.

After an iteration of carboard engineering, to borrow a term from Heinz, I designed a three bracket system, laser cut it and bolted it to the transmission. I then used one of my now favorite 2.5" exhaust clamps to attach the flexural brace directly to one of the exhaust tubes. The 'bang on the exhaust with my fist test' noted a massive reduction in vibration of the exhaust.

https://www.youtube.com/watch?v=uvz95Sx9ySc

Here are a few shots of the brackets installed:




And with the splash guard in place, showing full clearance everywhere:




What's the verdict?

Very big improvement, I was genuinely surprised at how effective this is. A bigger and broader improvement from this change than the other two I'd made to clamp the pipes together. It idles more like an m54 now than an s54, which I think is a very good thing and it's essentially imperceptible when switching the AC on and off, which wasn't the case before. The resonance near idle and at 1700rpm are absolutely completely gone, and the resonance at 3300rpm seems a bit attenuated and spread out a little, now between 3100-3300rpm. This might be the exhaust's new first excitation mode.

Here's the thing though, it affected essentially the entire rev band under 5000rpm in a big way. The engine is so much smoother when revving, and it's especially noticeable when blipping the throttle, or when engaging the clutch and pulling away from a stop. I hadn't noticed or pinpointed this previously, but there was a 1-2 oscillation change in the exhaust when doing those things. Unnecessary sloppiness. Now the engine makes rev changes and pulls away from a stop like a 330i - smoothly and without any secondary motions. Also more like my previous porsches, responsive with the only motion being the motion that matters. And to top it off, some of the resonance and vibration above 5k stayed, so it still has a bit of that raw supersprint header feeling when you're really on it and high in the rev band. Personally I think I'd rather it be smooth, but I expect most folks would appreciate keeping the feeling of those higher frequency vibrations.The whole rev band is very noticeably smooth now under 5k, even under load, with the exception of a less prominent bit of vibration between 3100-3300. And this is going to sound crazy, but I can swear I hear the lower frequencies in the stereo better.

I've got a complete 2.5" supersprint exhaust here (-20lb), as well as a 330i ZHP muffler (-10-15lb) that I'll likely swap in to drop the mass at the end of the exhaust to help raise the natural frequency even more. I'd still like to eliminate the 3100-3300rpm subtle vibration to make it non-m-smooth cruising on the highway, as that's 75-80mph for me. An added bonus with the ZHP exhaust is that it has a vibration damper already on it that I can swap out to tune out that last vibration mode.

I really want to A/B this against a stock M3 (will do soon), as I'd bet this is smoother than the M3 came from the factory now. And this is with 75k mile, 10 year old motor and trans mounts. I'll be A/Bing against a freshly built motor with all new mounts, so this should be a conservative comparison. I also have new mounts waiting for the oil pan gasket job I'm putting off.

So the ultimate daily driver gets even better. Hope you enjoyed this and I'd recommend doing the same to your car if you have 2.5" SS headers and section 1.