continued from above
The OEM roof weighed 96.1 pounds (24.1 for panel + 72.0 for sunroof cassette). The new AJ Hartman carbon fiber roof came in at 6.9 pounds, for a total savings of 89.2 pounds - way up high in the roof! Not only did we lose the equivalent mass of a "young adult" the interior gained about 2.5" of headroom. We also had ample access for building the roll cage.
The CSL carbon roof panel went on easily and bolts in place using 4 factory threaded bolt holes, which fit the roof section perfectly. Ryan had to do zero adjustment, custom fitting, or hole enlargement - it just fit.
Once the cage work is finalized and before paint this will be bonded to the body structure just like the factory E46 M3 CSL roof is, plus there are the four back-up bolts as well.
INTERIOR UNIBODY STRUCTURE REMOVAL
The back seat was never going to be used in this build, so to lose some additional weight we looked at the rear seat bulkhead structure and decided to remove it before the cage began. There is a lot of easy weight that can be removed from the back seat, and in our 2001 BMW E46 330Ci we found
63.8 pounds in the back seats + headliner and another
10.4 pounds in rear speakers and a few trunk brackets.
Compared to my 330, this M3 needed an even sharper scalpel this time. We weren't looking to "skin" this car and put it down over a tube chassis or anything, but redundant structures that could be removed would be. There was some easy weight loss in the rear seat bulkhead perimeter structure and rear window "speaker deck" panel - which would have their chassis stiffness more than replaced with roll cage structure. We will make lightweight interior panels to separate the trunk from the passenger cabin.
There were probably another hundred spot welds that were cut for all of these brackets, panels and sheet metal structures in the back seat area. These were cut into small pieces with a reciprocating saw and pried loose without warping or damaging the surrounding structures.
Of course I forgot to weigh all of this before the scrap metal guys came and picked it all up, but it was around 15-20+ pounds of sheet metal in addition to the back seats, interior panels, and trunk brackets that were also removed (with weights noted on our red 330).
Now the car was ready for a roll cage!
WHAT'S NEXT?
The intro post in this build thread has already run long, so we better cut it short. Nothing really earth shattering done in this first series of posts, just showing the steps needed to remove weight and add longevity to this E46 chassis. Again, my goal weight guesstimate is 2600 pounds soaking wet with a dry-sumped LS stroker, T56 Magnum, giant wheels and tires, wide body work, full aero, and the required door glass + heater + wipers required for street use.
In my next installment in this build thread I will show the roll cage fabrication work. I will also cover seat installation, custom "low profile" door panel construction, subframe reinforcement, the 8.8" Ford IRS diff swap, and more. We will discuss the classes we are building toward in NASA and Optima, and the rules/performance differences between them.
I tend to show details and pictures of this build and more "in real time" on our Facebook page and in our irregular "this week at Vorshlag" videos on our Youtube channel. Look for those and like/subscribe/whatever it is you are supposed to do there if you want to see the progress on this build sooner.
Until next time,