A shadow long cast.

A shadow long cast.

"In this Special Series, I document my CSL airbox experiences. I take you into my unboxing of my various airboxes, the hardware checklist, the tuning dilemma, installation notes and my driving impressions with proper sound clips.

In this entry, I document my unboxing impressions of my 2nd CSL airbox from Haimus: the updated Shadowline trim with a new-to-me gloss finish."


    In Fall of 2022, I embarked upon restoring, upgrading and changing the color of my E46 M3. The change of color to San Marino Blue was a core component of the project. Unfortunately, my previous CSL airbox had been spec'ed with then matching Phoenix Yellow stripes with the Haimus Racing logo. 

    It simply didn't match anymore.

    I also had second thoughts about the Frozen finish on the CSL airbox for this new build. The engine bay was going to be clear coated in gloss over San Marino Blue, creating a stage for the CSL airbox to pop. 

    An OE realignment. 

    Antonio reached out throughout Winter giving me a heads up on a new CSL airbox trim he was working on. His intentions were to take his airbox's finishing further upmarket by matching OEM aesthetics with two key components: black fittings and a superior gloss finish. 

    The market is moving upwards: cars are still appreciating and new owners are taking ownership of E46 M3s. Some of these owners want more than purely CSL noise: they want matching aesthetics and improvements from 20 years of knowledge and technology advancements. 

    The original CSL airbox had black anodized CNC fittings across the airbox. 

    As is common on OEM quality parts, the gloss clear coat finishing was superb across the airbox. 

    The "Shadowline" trim. 

    Antonio and his team had settled on the "Shadowline" nomenclature for this new trim along with the specific improvements from their now discontinued Premium Plus trim. 

    You could now order the Frozen and Gloss finishes in 2x trim lines. Here's a table recapping the available trims. 




    Available Finishes Gloss
    Gloss only
    Bungs Black anodized like OEM airbox Raw aluminum finish
    Finish Warranty 5 years 5 years
    Structural Warranty 5 years 5 years
    Finishing Extra
    • Polished
    • Matched weave pattern on bottom of airbox
    • Extra action to remove any surface imperfections
    • Ceramic coated
    • Polished. 
    • Matched weave pattern on bottom of airbox
    • Extra action to remove any surface imperfections


    My specs. 

    In the Spring of '23, we further chatted about launching the new OE matching trim line. A limited pre-order for 12x spots was offered to EuroConnex members. 

    I got on board the group buy and ordered a new naked gloss airbox and new snorkel for The Phoenix.

    I received the package by early July and grabbed detailed pictures covering the improvements. 

    The gloss aesthetics. 

    The gloss clear coat is a 2 component automotive grade clear. Multiple coats are applied to give the signature depth to the gloss clear. Additionally, the Shadowline trim is now ceramic coated to further enhance gloss quality. 

    The immediate reaction to the airbox is amazement at the aesthetics of a gloss clear coat on a CSL airbox. 

    You can see the smoothness of the clear, and continuous reflection of the lights' pattern. The ceiling mounted LEDs never, ever lie. They tend to emphasize any imperfections in a gloss clear. 

    Sections that you will never, ever seen when mounted to the S54 are still exemplary. 

    Imperfections were found underneath, there was slight clear coat popping underneath by the brackets. We could correct this with sand and polishing prior to installation. I'm frankly unbothered. 

    The carbon work. 

    The box retains the signature pre-preg and autoclave carbon construction, however further attention is put laying the weave to create aligned patterns. 

    Antonio and his team decided on a change from the OEM airbox. They lay the 2x2 weave in the opposite direction to OEM. When looking at the engine bay from the front bumper, the OE weave is laid towards the 3 o'clock direction.

    Haimus' weave flows towards the 9 o'clock direction. 

    When rotating the airbox to inspect every single aspect, you get a sense of the multi dimensional design of the CSL airbox. It's a much more complex piece than V8 carbon plenums.

    You get a sense for the craftsmanship required to rival the OE aesthetics quality of the CSL airbox for sections that will never be visible to any of us once mounted. 

    As the airbox's carbon eventually needs to connect together, the seam is created on the right hand side of the airbox, when looking at it from the front bumper. 

    The mold for each section was also renewed. Cues were taken from customer feedbacks from the previous version on slightly improving sections to ease fitting the OEM CSL air filter. 

    The carbon work is further noticeable on the internal sections near the snorkel opening. The internals are smoothened to optimize for air flow. There are no extra carbon layers visible to disrupt the weave's pattern. 

    The twisted pattern of the trumpets' 2x2 weave is visible from the outside as well.

    The OE+ touches.  

    The intention with the Shadowline trim is to match OEM. A key component was the use of black anodized CNC fittings. All CNC machined pieces are anodized black.

    The trumpets' threaded inserts extending beyond the airbox are the most obvious change in aesthetics.

    The black finish smoothens the overall aesthetic of the box. 

    The black finish hides away little machining details that were into this signature design from HaimusRacing. 

    All the CNC fittings for the crankhose and other fittings are anodized in matte black. 

    Showcasing the CNC fittings underneath the airbox is also an opportunity to remind the improved position of the Intake Air Temperature (IAT) sensor bung.

    It was moved closer to the filter's position to reduce heat soaking experienced with the original BMW M design. 

    Haimus spec'ed matte black bolts connecting the 2 components of the airbox. BMW had spec'ed standard silver bolts. This is highly visible and something I view as a valuable change from the original design. 

    Stepping back from the airbox, you get a perspective for the compounded effects of high gloss, and fully blacked out fittings. Everything is sleeker than the previous airbox I had fitted. 

    The plastic Tuba!

    Last but not least, I also sourced a new replacement snorkel for my airbox. I sold the previous unit to a local member. He wanted it, and it had slight damage from installation. A snorkel is bound to get scratched, you will eventually be disappointed if you opt for a carbon unit from other brands. 

    Carbon snorkels are expensive, and will get scratched. 

    The 3D printed ABS plastic snorkel is modest, subtle and does the job of feeding air from the lowest point of the engine bay. 

    The snorkel is compatible with the OEM CSL bumper ducting and it's original design. 

    The snorkel also comes with the required hardware to bolt into the airbox. The bolts' sleeve is now black instead of silver. 

    Up next: we await the S54's bulletproofing to refit the CSL airbox. 

    We'll revisit the MAP sensor conversion & installation along with final installed pictures, and [...] sound clips!

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