Custom Corner Light Ram Air Intake Box

The aero duct project began after upgrading the factory MAF to a repined modern unit with significantly lower restriction and reduced sensor latency. Throttle response and power delivery under wide open throttle noticeably improved, but it became clear that the real bottleneck was the lack of consistent cold airflow to the engine. The existing intake setup was pulling in hot underhood air, limiting the gains from the MAF upgrade. 

Initial attempts involved hand-laying fiberglass to form a custom duct, but curing issues with the first resin made the layup unusable. After switching to a better resin, I was able to complete a functional duct using the original corner light housing as a structural guide. This version had improved shape retention and surface finish, making it usable for initial testing.

However, the internal surface was still rough, and the coupler interface wasn’t perfectly round. These issues led to frequent disconnections under NVH and highlighted the need for a more refined approach.

I also tested a simplified version with a smooth exterior and a single 3 inch inlet hole. While it solved the fitment and sealing issues, it proved too restrictive to provide adequate airflow at higher RPMs. These trials helped define the core requirements for the final design: smooth internal geometry, proper flow volume, and secure coupler retention.

To solve the airflow bottleneck, I built a new intake system centered around a 6 inch velocity stack, routing it toward the front corner of the car to pull in cooler ambient air. The system used custom carbon fiber tubing joined with silicone couplers, and I incorporated custom-milled components to retain full functionality of the factory PCV return system.

To improve midrange torque, I also lengthened the intake piping. This change helped increase air velocity and volumetric efficiency in the middle of the powerband, making the car feel more responsive during partial and transitional throttle.

To reduce heat soak, I fabricated a small sheet metal shroud and positioned the intake as close as possible to the ram air duct outlet. While this provided some thermal shielding, the alignment between the intake and duct exit was off, and the entry angles were far from ideal.

I also switched to a filter with a center inlet opening, which allowed air to flow not only around the sides of the velocity stack but directly into its center. This improved the alignment between the ram air duct and the intake, creating a more efficient and direct airflow path. While it was a significant improvement, these changes made it clear that a complete redesign was needed to fully optimize flow, packaging, and thermal isolation.

To kick off the CAD phase, I scanned both the engine bay and the exterior front corner of the car. By merging the two scans, I was able to work in a fully integrated environment, ensuring seamless alignment between the airbox, velocity stack, and future duct geometry.

Rather than immediately modeling the duct, I focused first on positioning the velocity stack correctly. The goal was to create an airbox that aligned perfectly with the planned duct outlet at the front corner of the car, maximizing direct airflow into the intake.

I mocked up multiple silicone couplers with 22, 30, and 45 degree bends to test how the stack would line up with the intended duct path. The 30 degree coupler provided the best alignment, positioning the velocity stack directly in line with the ram air entry point. This orientation also allowed for smooth packaging within the available engine bay space.

I am currently in the process of printing version one of the airbox, which is designed to cradle the velocity stack and guide air into it from the duct. A lid still needs to be designed, but once I confirm hood clearances with the base print installed, I will begin modeling the upper portion of the box to complete the enclosure.

The first printed airbox base confirmed general fitment but revealed a few issues. The ducting was slightly off-center from the ram-air inlet, and several areas around the coupler and bodywork had interference fits. These clearances will be adjusted in the next iteration.

After seeing the mockup in place, I also decided to move away from the open, non-sealing design and transition to a fully enclosed system with a lid to isolate intake air from engine bay heat.

The first printed airbox base confirmed overall fitment but revealed a few issues. The ducting was slightly off-center from the ram-air inlet, and several areas around the coupler and bodywork had interference fits.

After reviewing the mockup, I moved away from the open, non-sealing concept and began developing a fully enclosed V2 design with a smooth, continuous duct. The goal was to better center the intake around the velocity stack to maximize the ram-air effect and take full advantage of the available space for increased airflow volume and efficiency.

The V2 airbox introduced a fully enclosed design with a smoother, more centered duct to maximize airflow volume and the ram-air effect. This version made better use of available space and incorporated revised clearances to eliminate the interference seen in V1.

During printing, a scaling issue caused a slight mismatch between the two halves, preventing them from fully bolting together. The test fit also revealed that I had misdimensioned the velocity stack filter, which kept the intake from fitting properly over the filter. Even with these setbacks, the test fit confirmed that the new duct geometry and overall layout were moving in the right direction.

V3 resolved the V2 scaling and filter-fit issues and finalized the fully enclosed 3″ intake system. The duct elbows and then expands quickly to 4.5″ diameter, using the bend’s natural flow disturbance to absorb the rapid volumetric expansion and distribute air more evenly into the main section.

After the 4.5″ outlet, the duct incorporates a 30 mm hexagonal air straightener, followed by a 150 mm long diffuser section with a continuous 7° wall expansion. This setup straightens and gradually decelerates the flow, minimizing turbulence and pressure loss before entering the main upper intake box.

The main plenum volume measures 7.448 L, precisely tuned for the 3″ inlet’s flow characteristics. At 40–60 mph freestream, the 3″ opening captures approximately 173–259 CFM, closely matching the 3.0 L V6’s mid-rev airflow demand of 190–220 CFM. This configuration maintains strong pressure recovery and throttle response while maximizing airflow efficiency in the 40–60 mph range.

The V3 mockup assembled smoothly, marking the first fully functional fitment of the enclosed airbox system. Aside from a slight bolt-hole misalignment on the mounting V, the assembly bolted up cleanly and all components cleared the hood without interference.

After a test drive with the PLA+ mockup, throttle response was noticeably snappier between 3000–5000 rpm, exactly as intended. The system has been driven a combined 20 miles without issues, confirming both the performance and fitment.

Since PLA+ softens around 55–60 °C (131–140 °F), it isn’t suitable for long-term use in the engine bay. The final version is now being printed in ASA-GF (glass-fiber reinforced ASA), offering a heat deflection temperature around 105–110 °C (221–230 °F) for excellent thermal and structural stability. Once fully printed, the part will be skinned in carbon fiber both to improve heat insulation and to add a bit of visual flair and craftsmanship to the finished assembly.

The V3 assembly printed in ASA-GF has performed exceptionally well throughout testing. The glass-fiber reinforced ASA shows no softening, warping, or heat fatigue, even after multiple heat-soak cycles in the engine bay. Fitment has remained tight and consistent, and the airbox maintains its alignment and sealing surfaces under all driving conditions.

During real-world driving, some fasteners began to loosen due to engine vibration. This isn’t a structural flaw in the design—simply the reality of mounting a composite system in a high-vibration environment. The final version will incorporate blue Loctite (medium-strength threadlocker) on the key screws to eliminate vibration-related loosening and ensure long-term stability.

To refine both the airflow strategy and the overall philosophy behind the design, I reached out to a forum of engineers, motorsport fabricators, and rally drivers for critique. Several pointed out that hex-flow style filters are generally more restrictive than beneficial, especially in sealed intake enclosures where smooth airflow and stable pressure recovery matter more than turbulence-inducing geometry.

Because the filter was designed to be fully removable, I was able to validate this firsthand. After testing the system with and without the hex-flow insert—and confirming the restriction issues—it has since been eliminated from the V3 configuration.

With the restrictive element removed and the ASA-GF structure validated, the V3 prototype confirms the system’s thermal stability, structural integrity, and mounting strategy. Only minor adjustments (threadlocker and fastener updates) are needed for production.