Black & Tan 332iT

[Bry5on]

What would it take to get / make a Mullet tune for those of us w/ CSL airbox + CSL software and different cams (288/280s)? Been doing a LOT of reading about datalogging, tuning, etc.

Mike

Realistically pretty unlikely. Either an engine dyno and a lot of time, or I’d need to daily that setup and iterate for several months. Sorry!

[Bry5on]

If I understand you correctly, you are saying previously you thought the hub pivoted off of the inner control arm joints and the trailing arms just set toe. But in actuality the hub pivots off the front trailing arm location and the control arms just set camber?

Not exactly, but something close to that yes. Previously I assumed that the rear control arms inboard termination point was close to the axis of the hubs. If that were true, you could calculate the instant center and roll center pretty accurately without factoring in the location of the trailing arm bushing.

The e46 hub is always pivoting around an axis that includes the trailing arm bushing on that axis. The second point that defines that axis is a virtual location where the upper and lower control arms meet (I’ll get to this in a second). If you extend that axis in three dimensions, the instant center is the point where that axis crosses an imaginary vertical plane that intersects both rear wheel/hub centers. Then the roll center is the intersection point of the left and right instant centers.

Ok, so that virtual point where the control arms meet (above). It’s always moving with suspension travel, it’s not technically fixed in space like a true semi trailing arm. However! Because the two inner mounting locations are SO close together, that point baaarely moves as we sweep through suspension travel, which effectively approximates a static point, like a semi trailing arm.

So in conclusion, the e46 is not technically the same as a semi-trailing arm rear suspension, but practically speaking it behaves the same with a very small deviation. That amount of small deviation is related to providing the degrees of freedom necessary to easily adjust camber and toe without changing the suspension geometry much at all.

So, for all intents and purposes, a semi-trailing arm suspension that has adjustable camber and toe. Hopefully that was followable.

[nuc1]

What would it take to get / make a Mullet tune for those of us w/ CSL airbox + CSL software and different cams (288/280s)? Been doing a LOT of reading about datalogging, tuning, etc.

Mike

[George Hill]

2) Tonight's realization after modeling the e46 rear suspension: The e46 suspension is just a semi-trailing arm suspension that accommodates camber and toe adjustments. It's really just an evolution of the e30 and prior designs. Suspension behavior is much more in line with a semi trailing arm than a multi-link suspension due to the placement of the members. Can't believe I hadn't realized this until now, duh.

If I understand you correctly, you are saying previously you thought the hub pivoted off of the inner control arm joints and the trailing arms just set toe. But in actuality the hub pivots off the front trailing arm location and the control arms just set camber?

[heinzboehmer]

2) Tonight's realization after modeling the e46 rear suspension: The e46 suspension is just a semi-trailing arm suspension that accommodates camber and toe adjustments. It's really just an evolution of the e30 and prior designs. Suspension behavior is much more in line with a semi trailing arm than a multi-link suspension due to the placement of the members. Can't believe I hadn't realized this until now, duh.

Looking from the bottom of the car, the lower dashed line in this picture depicts the axis of rotation of the 'trailing arm' as the instant center is basically stationary throughout suspension travel:

Woah, mind blown.

[Bry5on]

A few things:
1) Euro Mullet tune v26 seems to be on the money now. I'm happy with cold start operation and a couple days in it still seems to be butter smooth everywhere in the rev band. More seat time to come, but hopefully this is the last rev

2) Tonight's realization after modeling the e46 rear suspension: The e46 suspension is just a semi-trailing arm suspension that accommodates camber and toe adjustments. It's really just an evolution of the e30 and prior designs. Suspension behavior is much more in line with a semi trailing arm than a multi-link suspension due to the placement of the members. Can't believe I hadn't realized this until now, duh.

Looking from the bottom of the car, the lower dashed line in this picture depicts the axis of rotation of the 'trailing arm' as the instant center is basically stationary throughout suspension travel:


3) The hubs are slightly rearward of the diff output flanges, about 20-30mm. This is probably to keep from passing the CV joint through its center axis position if I had to guess.

4) There is quite a lot of anti-squat in the e46, but we already knew this. Wheel hop!

[Bry5on]

awesome thread and nice daily that you are building. what kind of program did you used to compare the binaries? it's time consuming with tuner pro and loading different xdfs all the time.

Oh boy. Tuner pro, excel, a bit of Python. For logs, megalogviewer, datazap.me, excel. And lots of time, it’s definitely time consuming.

[Zekarus]

awesome thread and nice daily that you are building. what kind of program did you used to compare the binaries? it's time consuming with tuner pro and loading different xdfs all the time.

[D-O]

Well, I picked up myself one of these 3D scanners finally, so today was time to get my first scan and model created. The rear suspension.


Here's a link to the results, this is a scan at factory ride height, suspension compressed. You can peruse around yourself, take measurements, etc: https://s.digital3dcloud.com/space/0...0155&sharePwd=


I wanted the geometry and locations of the diff/axles for the next project, a proper multi-link rear suspension. Current plan, which looks pretty doable, is to build a custom subframe with e39 rear suspension pickup points. Then bolt in a full e39 rear suspension with some e60 wheel bearings/hubs and I should be able to just bolt my wheels back on and go. Piece of cake.

You will undoubtedly make it look like a piece of cake.

Really impressive build. Thanks for sharing.

[Bry5on]

Well, I picked up myself one of these 3D scanners finally, so today was time to get my first scan and model created. The rear suspension.


Here's a link to the results, this is a scan at factory ride height, suspension compressed. You can peruse around yourself, take measurements, etc: https://s.digital3dcloud.com/space/0...0155&sharePwd=


I wanted the geometry and locations of the diff/axles for the next project, a proper multi-link rear suspension. Current plan, which looks pretty doable, is to build a custom subframe with e39 rear suspension pickup points. Then bolt in a full e39 rear suspension with some e60 wheel bearings/hubs and I should be able to just bolt my wheels back on and go. Piece of cake.

[Bry5on]

Now that the weather is cold again, I’m using the heated seats a couple times a day. And once again noticing the aftermarket-ness of the elements that were stitched in when the leather was done.

Two things bother me:
1) The stock seats heat up super quick, these take forever to get to temp
2) They don’t work when the seats are cold! Kinda defeats the purpose.

So I decided to take matters into my own hands. I purchased e39 heated seat elements a while back and decided I was going to reverse engineer the heated seat elements to make my own. Well, I took all the measurements and ended up deciding to just modify the e39 elements as they were a pretty close size match for what I wanted.

Some specs (measurements are close enough, used my fluke DMM):
AMX elements, 4.6 ohm total impedance. 9.2 ohm seat bottom and 8.1 ohm seat back
e39 elements, 1.2 ohm total impedance. 2 ohm for the bottom and 2 ohm for the back

The factory elements are rather simple, just a stranded plated copper 28-29AWG wire with a very thin, likely teflon, jacket. The seat bottom has a thermocouple that I didn’t bother measuring, but that’s it. The back and bottom heating elements are wired in parallel.

The measurements explain the slow heating story, the 4x impedance means that they heat with 1/4 the power (P=V^2/R in this case). So the math agrees with the butt.

The seat bottom mostly fit without major modification, but the back needed a bit of extra work. What started as a rectangular piece went through a transformation to an element that supports a nice warm hug. Some photos below.

Overall, works like stock now. Happy with this.

[0-60motorsports]

CSL Cams and Valves, Only thing missing from my car LOL

[Bry5on]

Finally tackled the oil pan gasket. Fun job!



Also while I was at it, I replaced the AC condenser, as a last ditch effort at helping the car cool better on steep uphills on hot days. If this doesn’t do it, the logical last thing to check would be the head gasket, but there’s no lost coolant over tens of thousands of miles, so I’m a bit stumped.



Also in the interest of getting the cooling system in line. The M3 belly pan has a plastic support bonded to its top side. This bonded piece supports the bottom of the radiator duct to prevent it from blowing air under the oil cooler. Well, the non-m belly pan sits about 3/4” too low to support this, so I blocked it up with foam to achieve the same effect as the M3. Anyone with a swap car should do the same!


And last, swung by a friend’s place and found two very clean LSB CSL replicas there. One in the middle of getting CSL cams and valves. Nice cars.

[George Hill]

Ah so let's say if you're pulling the front seats from a desirable complete interior, someone is well within their rights to swoop by and snag the rear?

The car is yours, the etiquette IMO is to ask the person pulling parts what they are getting and if its not something you want then tell them what you want and if you aren't in their way go ahead and pull them with their permission.

[usdmej]

First come, first served.

Ah so let's say if you're pulling the front seats from a desirable complete interior, someone is well within their rights to swoop by and snag the rear?