The Master Mold Creation Process

The Master Mold Creation Process

"On April 29th 2022,  I launched a crowdfunding project to create a new 1:1 E46 M3 CSL carbon diffuser option on the market. 30x members backed the project in a few days 🙏

In this special series written in collaboration with René at, I document the entire ideation, development, master & negative mold production process along with my unboxing impressions and final fitment

This journal entry documents the unboxing impressions and my ordering recommandations."


How this differs from all currently available CSL diffusers. 

All current CSL diffusers on the market are made by creating a negative mold of a CSL diffuser. 

This is good, but not perfect.

The CSL diffuser used to make the mold can have aged and warped. The negative mold has a limited capacity for production. After it is worn, you need to make another negative mold by sourcing another Genuine CSL diffuser.

Some molds were clearly made from an aftermarket part as is often the case with eBay & Alibaba suppliers.  

It is why many eBay & Alibaba diffusers do not fit well. The prices are low, the initial craftmanship is poor and the return on Investment is made by extending the lifetime of the negative mold beyond its normal lifespan. 

CarboProject's master mold.

This positive mold is an actual 1:1 replica of the Genuine BMW CSL diffuser. 

The milling process was executed over multiple days on a 3 and a 5 axis milling machine. 



The original model is now finished with milling. 

It will get a high gloss epoxy resin coating after which it is ready to make the negative mold. 

The negative molds themselves will be made from pre-preg & autoclaved carbon fiber. It is from this mold that the CSL diffusers will be made from. 

With the master positive mold completed, we will now have a reliable, durable source for 1:1 Replica CSL carbon diffusers. 

Epoxy specifically made for pre-preg carbon.

René uses UREOL® epoxy resin. It is optimally tailored to the requirements of carbon composite mold making. Its applications are in the temperature range up to 140°C, especially well suited for prepreg carbon manufacturing. 


The release agent application & precise milling in preparation for laser cutting. 

As of June 2nd 2022, René has applied the 8x coats of release agent in preparation for the negative mold creation. 

The process takes over 4 hours of careful application. 

The positive master mold was then further CNC milled on the edges and brackets to prepare for the final laser cut. 

This process requires extreme precision and is a major component to the OEM fitment we aim for. 

You can see the precise milling in orange on the picture below. 

Negative Mold Creation.

As of June 8th 2022, René has created the 1st negative mold. Made from carbon fiber, this mold will be used to create the actual production units!

The mold is further reinforcement by adding carbon fiber plates to ensure the mold stays true during production and autoclave process. 

The negative mold will now be finalized by applying the various layers of release agent needed to start production. 

The 2nd Negative Mold.

René is re-investing the initial revenue into further production capacity by developing a 2nd negative mold for production. 

This will enable the community to get their hands on this carbon diffuser en masse with respectable delays. 

Shout to René for supporting EuroConnex and investing in the future. 

The First Pre-Production Units

The cookies are finally out the oven and icing got applied :) 

There it is! My Phoenix Yellow 1:1 CSL Carbon Diffuser with CSL matching 1x1 weave pre-preg carbon fiber is produced, painted and currently curing before shipment. 

There were lots of questions surrounding the paint like. The answer from René was this would be naturally dictated by the ridge. 

It was difficult to understand for most, understandably so. 

I'll let the pictures speak for themselves :)


Up next: unboxing impressions and my recommandations on specs. 



Leave a comment

Please note, comments must be approved before they are published

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.