Black & Tan 332iT

[Suspension Decoder]

Bry5on, greetings!

Our uber-moderator recommended I contact you. In a brief review of the first and last pages of your build thread, I can see you're extremely thorough. It also looks like you're in San Diego? I would love for you to experience a Fat Cat Motorsports suspension - I have the top-end Stage 3 Ultimate on my E46 330i right now (baby M3, not S54 swapped yet like your wagon, but lightened and tuned for track/autocross). The balance between grip and comfort is very good for a track/autocross-focused suspension.

I am leaving CA in a couple weeks for a relocation to Birmingham, AL, though would love to drive down (perhaps to LA?) and meet up with you! First, a phone chat would likely be a good start. My cell is 408-221-8247.

Cheers,
Jalal (Shaikh @ Fat Cat Motorsports)

[Bry5on]

Bry5on, greetings!

Our uber-moderator recommended I contact you. In a brief review of the first and last pages of your build thread, I can see you're extremely thorough. It also looks like you're in San Diego? I would love for you to experience a Fat Cat Motorsports suspension - I have the top-end Stage 3 Ultimate on my E46 330i right now (baby M3, not S54 swapped yet like your wagon, but lightened and tuned for track/autocross). The balance between grip and comfort is very good for a track/autocross-focused suspension.

I am leaving CA in a couple weeks for a relocation to Birmingham, AL, though would love to drive down (perhaps to LA?) and meet up with you! First, a phone chat would likely be a good start. My cell is 408-221-8247.

Cheers,
Jalal (Shaikh @ Fat Cat Motorsports)

Nice to see you in here! Big fan of the spreadsheet you’ve been hosting for ride calcs. Thank you. If you’re interested, I’ve modeled roll, jacking and travel earlier in this thread as well.

I’ve been chasing chassis (vs suspension) stiffness and have roughly doubled the torsional rigidity of my e46 at this point. I’m actually pretty happy with the stock M3 ride frequencies and travel (my touring corner weighs very similar to an M3), just not in love with small bump sensitivity performance. The stiffness increases in the chassis have been super eye opening for grip, chassis and suspension/tire control. Next, if I can make the front struts act more like a constant cylinder than a wet noodle by redesigning the front knuckle, I figure I can set myself up to best position the dampers up for success by reducing some stiction and undamped flex.

I was actually pretty local to you for the past 8 years and only moved to San Diego two months ago. It would have been great to A/B drive both cars. Maybe I’ll come back to visit and can take a rain check.

[Suspension Decoder]

Nice to see you in here! Big fan of the spreadsheet you’ve been hosting for ride calcs. Thank you. If you’re interested, I’ve modeled roll, jacking and travel earlier in this thread as well.

I’ve been chasing chassis (vs suspension) stiffness and have roughly doubled the torsional rigidity of my e46 at this point. I’m actually pretty happy with the stock M3 ride frequencies and travel (my touring corner weighs very similar to an M3), just not in love with small bump sensitivity performance. The stiffness increases in the chassis have been super eye opening for grip, chassis and suspension/tire control. Next, if I can make the front struts act more like a constant cylinder than a wet noodle by redesigning the front knuckle, I figure I can set myself up to best position the dampers up for success by reducing some stiction and undamped flex.

I was actually pretty local to you for the past 8 years and only moved to San Diego two months ago. It would have been great to A/B drive both cars. Maybe I’ll come back to visit and can take a rain check.

Glad you've found those calcs helpful - I'd be happy to check out your modeling. Any idea what pages / what part of your build thread to aim for when searching??

Chassis stiffness is magical. I learned this from my Miata days. Interesting how much room for improvements exists on the M3 as well. Your M3 dampers are jacking down into the bump stops, have a TON of compression and rebound in the rear, and have ZERO high-frequency softening capability (which is what my Ripple Reducer provides, inspired by off-road racers who have been drilling small holes in their pistons for decades to filter road rumble). The behavior isn't unique to the E46 M3, but it's all to familiar when I look at sport sedans / sport coupes.

I would be happy to meet you in LA sometimes before I go if you want to experience first-hand what I consider a well-optimized GT / Dual-Purpose suspension (frequencies around 1.9 Hz / 2.1 Hz). I'd have the bulk of the drive so it's your call. I've had a lot of people decide to work with me without demo rides. Obioban / Ian has a setup from me on his E46 M3 and I'm doing to build one for his 128i that includes more recent enhancements to my Ripple Reducer per conversations and calculations with an Mech Engr customer.

The rain check would be driving to Alabama so I've got two weeks if we want to make a meet happen. I can drive during the week so it's not limited to weekends. Maybe sleep on it and see if this appeals to you?

[Bry5on]

Glad you've found those calcs helpful - I'd be happy to check out your modeling. Any idea what pages / what part of your build thread to aim for when searching??

Chassis stiffness is magical. I learned this from my Miata days. Interesting how much room for improvements exists on the M3 as well. Your M3 dampers are jacking down into the bump stops, have a TON of compression and rebound in the rear, and have ZERO high-frequency softening capability (which is what my Ripple Reducer provides, inspired by off-road racers who have been drilling small holes in their pistons for decades to filter road rumble). The behavior isn't unique to the E46 M3, but it's all to familiar when I look at sport sedans / sport coupes.

I would be happy to meet you in LA sometimes before I go if you want to experience first-hand what I consider a well-optimized GT / Dual-Purpose suspension (frequencies around 1.9 Hz / 2.1 Hz). I'd have the bulk of the drive so it's your call. I've had a lot of people decide to work with me without demo rides. Obioban / Ian has a setup from me on his E46 M3 and I'm doing to build one for his 128i that includes more recent enhancements to my Ripple Reducer per conversations and calculations with an Mech Engr customer.

The rain check would be driving to Alabama so I've got two weeks if we want to make a meet happen. I can drive during the week so it's not limited to weekends. Maybe sleep on it and see if this appeals to you?

Here’s the spreadsheet - for accuracy with roll and travel you’ll need to enter CG height as well as the corner weights. It seems a stock M3 is around 21” and a weight reduced track M3 might get as low as 19” based on the measurements I’ve seen so far. The sheet will also calculate new weight distribution numbers for added/removed mass in x, y, z coordinates. Some of the assumptions that simplified the model came from my 3D model of the suspension geometry, which I think is hyperlinked from the excel doc somewhere in there.

Im pretty busy with my day job (I’m also a mechanical engineer, mostly rockets, spacecraft and automotive body in white work to date) so I don’t think I’ll be able to coordinate anything within the next couple weeks but maybe heinzboehmer and or tlow98 can take you up on that as they’re local to you on the peninsula. They’re both also engineers with similar OCD and are quite familiar with my car and its various developments.

Personally I find 1.9/2.1Hz a little high for me but I’m open to new takes with more appropriate damping. Prior cars in the last two decades have had lots of custom suspensions (all pitch balanced, roll centers in the right place, I did my homework) and I usually find that for my daily driver I enjoy about the 1.6 Hz range. Any more than that and it seems to trend too far down the “GT3 daily driver” spectrum for me. My last 991 911 had an aftermarket controller on the sport PASM dampers which helped a lot during daily driving but ultimately I wished for a softer/longer spring even so. I think that car was up to 1.7/1.8 or so in the rear if memory serves?

In any case, excel sheet here: CG location change_332it.xlsx

[Suspension Decoder]

Here’s the spreadsheet - for accuracy with roll and travel you’ll need to enter CG height as well as the corner weights. It seems a stock M3 is around 21” and a weight reduced track M3 might get as low as 19” based on the measurements I’ve seen so far. The sheet will also calculate new weight distribution numbers for added/removed mass in x, y, z coordinates. Some of the assumptions that simplified the model came from my 3D model of the suspension geometry, which I think is hyperlinked from the excel doc somewhere in there.

Im pretty busy with my day job (I’m also a mechanical engineer, mostly rockets, spacecraft and automotive body in white work to date) so I don’t think I’ll be able to coordinate anything within the next couple weeks but maybe heinzboehmer and or tlow98 can take you up on that as they’re local to you on the peninsula. They’re both also engineers with similar OCD and are quite familiar with my car and its various developments.

Personally I find 1.9/2.1Hz a little high for me but I’m open to new takes with more appropriate damping. Prior cars in the last two decades have had lots of custom suspensions (all pitch balanced, roll centers in the right place, I did my homework) and I usually find that for my daily driver I enjoy about the 1.6 Hz range. Any more than that and it seems to trend too far down the “GT3 daily driver” spectrum for me. My last 991 911 had an aftermarket controller on the sport PASM dampers which helped a lot during daily driving but ultimately I wished for a softer/longer spring even so. I think that car was up to 1.7/1.8 or so in the rear if memory serves?

In any case, excel sheet here: CG location change_332it.xlsx

Thanks for the spreadsheet and notes. Understood on your time constraints. I'll ping heinzboehmer and tlow98 individually or see if we can coordinate a group meet. There's an event on Sunday in Morage 'Estate of Mind' I'll be attending as a vendor. We'll have Christina there plus an F31 328xD wagon with FCM Elite Stage 3 Ultimate at ~1.6 / 1.8 Hz.

I agree that for more comfortable daily-driving, capping the rear at ~1.8 Hz is ideal. Transmissibility starts to increase rapidly above 1.8 Hz. I used to daily 2.2 / 2.4 Hz and with all the wizardry I can employ, it was quite tolerable. Now, with even more enhancements to high-frequency noise reduction (Ripple Reducer) and further optimization of damping ratios (it's amazing how little you really need when you get Flat Ride set up properly), at ~1.9 / 2.0 Hz Christina feels better than most sports cars from the factory - and has more grip as well. 1.3g on 255's (200 treadwear BF Goodrich Rivals).

The 991s when you include bump stop interactions are well north of 2 Hz. Those Porsches are a bit of a mess. Even on springs alone, Porsche has continually increased the base ride frequencies every generation. I think the 991 is the first when they didn't overdamp the holy heck out of the suspension, but it still has a strong rebound bias and is far from optimal.

If / when I meet up with the Peninsula M3 crew, they can report their observations back to you.

[Bry5on]

Test fit of the heat shield went well, miles of clearance to the tie rod and control arm. Definitely room to play with ackerman if one so desired, or to move KPI and scrub radius a bit.

Anyone here have a 3D section model of the CSL/ZCP or regular M3 brake rotor? Looking for a few key dimensions to verify clearance as I modeled my shield off of a factory M3 heat shield scan.

[Bry5on]

Alright, I forked out the $400 for a Fusion subscription and generative design tokens and finally ran the double clamp version of the steering knuckle.. You'll note in this version that we've reduced displacement at the top of the strut tube to 2mm, which now means <.2 degrees of camber loss at 1.6G corner loads, and we've introduced a simpler to machine pair of inserts in the control arms and tie rods. You'll also see that I didn't explore the saddle clamp idea as it would have been a mass penalty. This double clamp version is only .15kg heavier than the single clamp version and there's technically room for me to optimize this even further to get down to weight-neutral.

Anyway, lots of pictures of the parts tell the story:


And on to the simulation results:

[Obioban]

Alright, I forked out the $400 for a Fusion subscription and generative design tokens and finally ran the double clamp version of the steering knuckle.. You'll note in this version that we've reduced displacement at the top of the strut tube to 2mm, which now means <.2 degrees of camber loss at 1.6G corner loads, and we've introduced a simpler to machine pair of inserts in the control arms and tie rods. You'll also see that I didn't explore the saddle clamp idea as it would have been a mass penalty. This double clamp version is only .15kg heavier than the single clamp version and there's technically room for me to optimize this even further to get down to weight-neutral.

Anyway, lots of pictures of the parts tell the story:


And on to the simulation results:

Freaking amazing.

... we need a configurator. Choose your own caliper/steering rack :P

Have you priced out metal 3D printing a pair?

[Bry5on]

Freaking amazing.

... we need a configurator. Choose your own caliper/steering rack :P

Have you priced out metal 3D printing a pair?

Ha, yeah. The easiest addition is actually the F80 M3 brakes, as it's just a matter of moving the brake caliper mounting bosses 3mm toward the inside of the car and re-running the analysis. And honestly I'm not sure why anyone would really prefer the ZCP/CSL steering ratio over the non-m ratio

I've priced out printing, yeah - it's a few grand per pair, then you need to add the four machined 4340 inserts into the picture.

We've now shaved it down to a .09kg weight penalty vs the single clamp version - I think I'm going to call this done:

[Obioban]

I'm not sure why anyone would really prefer the ZCP/CSL steering ratio over the non-m ratio

To keep the DSC happy?

[Bry5on]

To keep the DSC happy?

Just manually write the non-m ratio into the DSC using NCS expert, and done. No problems with DSC

[YoitsTmac]

That thing is spooky! Nothing like anything I've seen. Is your 1.6G load testing peak or average load test? What happens when you hit a hard bump at full load?

What is the issue re clearance to ZCP rotor? Isn't your rotor mounting surface distance to the tie rod equal to stock when looking down on the Z axis? If geometry is staying the same, then those parameters should all be equal, including clearance, no? I'll have to give you my stock clearance of my BBK, which Heinz notably pointed out the PO cut the shield or else I'd give you the measurements you're looking for

[Bry5on]

That thing is spooky! Nothing like anything I've seen. Is your 1.6G load testing peak or average load test? What happens when you hit a hard bump at full load?

What is the issue re clearance to ZCP rotor? Isn't your rotor mounting surface distance to the tie rod equal to stock when looking down on the Z axis? If geometry is staying the same, then those parameters should all be equal, including clearance, no? I'll have to give you my stock clearance of my BBK, which Heinz notably pointed out the PO cut the shield or else I'd give you the measurements you're looking for

Yeah the output is pretty wild. I used some conservative numbers in there (full half car weight on the strut), extra loads for dynamic steering inputs at the limit, and also chose 1.6G as a pretty conservative limit case. The rest is taken up by the safety factor.

Clearance to the ZCP rotor is really just for verification purpose as I never scanned a rotor, even though it's the same as stock (plus those heat shields were a little bent . Trying to make sure I validate all possible mistakes here before I place any expensive orders. I got a STEP file of the ZCP rotors so I'll print a section and do a digital and physical test fit shortly!

[enjoy_m3]

Very cool, so many cool parts comming between you and the carbon doors. Excited about building my wagon, funding not so much, lol. I have a set of f80 brakes sitting if you need to test fit.

[D-O]

Wow. Just wow...