How we worked with 'Construct3D' to develop a bespoke ECU Cover
A blog by Director of Motorsport, Dr. Kieran Reeves
Many of you who follow our journey will know that this year we embarked on an ambitious project to rebuild our Mosler MT900R. Alongside a new engine and a complete overhaul of the mechanical systems, we decided it was the perfect time to replace the entire electronics and electrical system.
After several months of designing and planning the wiring harnesses, I encountered a challenge regarding the ideal placement of the Engine/Transmission Control Unit (ECU) and Power Distribution Module (PDM).
The harness design was intended so that the control modules could be mounted on the firewall, within the cabin. To avoid having to create a harness with wires doubling back on themselves, and due to packaging constraints, the ECU harness needed to run down the back of the PDM heat sink plate and connect to the ECU plugs vertically (Fig. 1), rather than the typical configuration where each harness connects to the two ECU plugs from either side.
This presented a challenge, as 90-degree plugs and covers are readily available from various manufacturers, but a vertical design was not. That’s when I began working closely with Construct3D (https://construct-3d.com).
It quickly became clear that this company could print in a range of materials, and they proudly claim to manufacture the fastest 3D printers in the UK. Construct3D offers in-house design and drawing services, provides material advice, and prints custom components for clients. This sparked ideas for future collaborations with them—especially as their fast-printing capabilities could be useful for producing and supplying 3D parts at the circuit during race weekends. Stay tuned to our blog series for updates on these exciting projects!
Returning to the current challenge, although we have access to CAD software and a 3D printer, I wanted something of production-level quality. I also saw this as an opportunity to collaborate with a cutting-edge company. So, I invited the team from Construct3D to the NMA headquarters to discuss the issue. Therese and Jacob from Construct3D are incredibly knowledgeable about 3D printing, rapid prototyping, and the materials that can be used in various environments.
After initial discussions, they began by measuring the harnesses and clearances while exploring potential solutions. I provided a 3D model of the ECU so that Jacob could create some design options that we both felt would work.
Within a few days, they sent a 3D CAD model for approval, and after giving the go-ahead, they quickly printed a test piece to ensure appropriate fitment. This allowed me to review it in situ and provide any feedback for final adjustments.
The final design comprised three parts: a back plate for mounting to the Mosler’s firewall, a smaller front section secured with M5 bolts to hold the ECU firmly against the back plate, and a harness cover with magnets, enabling quick and easy access to the ECU plug and wiring for diagnostics (Fig. 2).
After initially installing the test piece (Fig. 2), I realised that the magnets might not be strong enough to handle the harsher conditions of kerb-riding and other rigours of the racetrack. To address this, I decided that two of the magnets should be replaced with M5 screws. The areas needing modification were identified and marked accordingly, as shown in the bottom left image of figure 2, highlighted in purple.
The harness cover was also designed with a relatively large clearance for the harness wires to emerge. This was an intentional design feature in the prototype to allow us to assess the required safe clearance once fully installed in the car and report any necessary changes.
Figure 3 shows the initial size and diameter of the orifice, and I determined that it could be reduced by 22mm to achieve a tighter fit.
A quick email, including pictures and a description of the required changes, was sent to Jacob at Construct3D, and the final product was soon produced (Fig. 4).
All three sections of the ECU cover took a total of 3 hours and 40 minutes to print, weighing just under 300g. The material used is Polyethylene Terephthalate Glycol (PETG), a modified version of the plastic commonly found in water bottles. PETG boasts excellent impact absorption and can withstand even the hottest conditions, making it ideal for motorsport applications.
The parts were printed with a hollow structure, filled with a 25% internal lattice. This provides the strength of a bone while keeping the part lightweight.
To ensure durability, I added a seal to prevent water ingress and protect the wiring harness (Fig. 5) before completing the final installation (Fig. 6).
With just some small wiring harness housekeeping left to do, the Mosler will soon be hitting the track in full force during upcoming test sessions.
Stay tuned for further updates on the Mosler’s progress via our social media channels.
I want to extend my sincere thanks to Construct3D, especially Therese and Jacob, for collaborating with me on this project. I’m excited to work on several more projects with them in the near future.
Dr. Kieran Reeves
Director of Motorsport
You can reach Construct3D through their website at https://construct-3d.com/contact/, via email at admin@construct-3d.com, or follow them on their social media platforms by clicking the buttons below.