01/17/2026
This has been sitting in the office waiting for its install on a customer’s car. The CSL Plenum for the BMW S85.
It didn’t arrive yesterday (it landed in the fall), but the excitement is still the same. The S85 “CSL-style” plenum has always been one of those mythical, rarely seen parts tied to the E60 M5 CSL “what if” story, and seeing it as a real, finished product is genuinely special. The team in Great Britain turned that idea into a showcase product.
What makes it different from the OEM S85 plenum?
With the full CSL intake, the side inlets to the plenum are roughly twice the size of OEM, which supports higher airflow potential. Another major change is the velocity stacks: compared to the OEM plenum, they have about a 10% larger opening, and they’re oriented to face the inlets. On the original S85 plenum, space limitations mean some stacks face the lower section of the plenum instead, similar to the S65 layout where everything is aimed toward the single inlet.
This setup requires Alpha-N, but it’s straightforward, and it comes included with the kit, so the calibration path is clearly defined.
This kit also includes closed carbon intakes. The S85 runs hot even during normal driving, so under-hood temperatures rise and intake air density drops. A sealed system pulling air from outside the engine bay helps keep intake temperatures lower and the airflow more consistent.
Bonus part!
This customer’s setup is also getting a TTV Racing lightweight SMG flywheel, dropping weight from 14.3 kg to 8.5 kg. Less rotating mass thus we will get more responsive engine feel, quicker rev changes, and a sharper overall driving character.
Install + footage coming soon.
