E46 REAR BASH BAR AND DIFFUSER

Whether on or off the track, aerodynamics plays a vital role in not only performance, braking and tracking, but also helping in achieving that ‘feel’ with the car. A BMW E46 came in for a rear diffuser install as well as a rear bash bar - a more simple take on the bash bar was set out as it’d come to serve more as a singular lifting point, while also adding some more protection to the rear. No more lifting from the rear diff or removing side skirts to fit a jack underneath.

With the diffuser mocked into place, measurements were taken both fore and aft, as well as raked to be inline with the underside of the chassis as well as the sides of the rear fenders.

With the diffuser now mounted at the front most mounts, minute adjustments were made for optimal performance.

A secondary mount was fabricated to better hold the center-rear most portion of the diffuser. Additional mounting provisions will mount to the outermost sections of the diffuser and tie into the bash bar via adjustable tie rods; opposing heims at both ends will then allow for further adjustments of both lower winglets.

I opted to extend the bash bar mounting plates further down - the reason being, it would allow me to further cut the uprights and maintain full contact with the mounting plate. Trimming and final fitment of the mounting plate will be completed once the bash bar is complete and thus the excess can be removed. The bolts shown are temporary as the finalized versions will have bolts welded to the plate for easier install and removal.

Maintaining continuity in the bend and notch for the rea jack point was paramount as the lower end of this standoff will be cut down and sleeved. It will also pass through the diffuser to allow for jacking up of the vehicle whilst not requiring the removal of said diffuser.

I opted to build this section on the bench for a multitude of reasons. The first being that any warping would be isolated to a smaller ‘scrap’ piece of tube (the same size and wall thickness the bash bar would be built out of), and it would also allow for the overall ease of welding the underside of the 2 adjacent 45deg notches.

Note that the sleeved and bent section of tube is overlayed - the smaller standoff towards the right slots into place. A smaller 1 1/4 tube was inserted, rosette welded and blended out; This inner tube slides into the main section while the larger 1 3/4 sleeve overlays it for dual security when in use.

Here you can see the standoff inserted in and holding in place.

With the bash bar now located, the uprights were tacked into place. Alignment of the jack point as well as the centering of the bash bar was now in order. Additional tabs for quick latch mounting and standoffs which will allow the outer diffuser winglets to be supported and adjusted were then added.

With the jack point bar located and centered, I was able to clearance out the diffuser to allow it to pass through.

Note the bunged standoff that allows the tow strap to be mounted or removed for a sleeker look. The OEM cover on the bumper still snaps in place for a seamless finish. Here you can see the tabs tacked in place for the quick latches and diffuser stiffeners.

The bumper is now mocked up, with the tow point centered through the OEM hole on the bumper. An OMP strap was then added to match the setup on the front bash bar.

With the the bash bar fully prepped, I was able to lay down some paint and get it installed. New hardware was used throughout. Note the side diffuser strut bars are mounted too allowing for full adjustment of the outermost winglets of the diffuser. Last up on the list is to mock the bumper in place and install the quick latches.

Another task on the to-do list was to remount the Recaro Seat. The owner and I had previously mounted the seat to stock slider/riser rails - to utilize all the stock functions and adjustments, it meant that the seat sat relatively higher up. The task, utilize most of the adjustments but now get the seat lower.

For these revisions, I opted to design a flat mount, and trim off any excess of the OEM mount to allow for the seat to sit optimally, and as low as possible.