Reference
Splitter Extractor Cowl
Bolt-on undertray extractor: a flat countersunk flange with a single smooth swept cowl rising off it into one large tunnel-shaped exit. Vents the high-pressure region under a splitter or flat floor out over the flange's trailing edge.
Printing it
- Material
- PETG / ASA
- Minimum wall
- 1.6 mm
Print flange-down with supports inside the cowl only. The outer surface is self-supporting -- the flanks lean outwards the whole way up -- but the tunnel roof is a shallow overhang for its full length and will droop without support under it. To avoid supports entirely, stand the part on its exit face with a brim: nothing then overhangs, at the cost of a tall, tippy print. The default 230 x 200 mm flange fits a 256 mm bed; the Fusion original's 400 x 310 mm does not. PLA is fine this far from brake heat, but PETG or ASA survives stone strikes and summer tarmac better.
Parameters
Every number this part is generated from. The geometry is built from these rather than scaled from a fixed model, so a value you can measure off your own car is a value you can type in.
Mounting flange
| Parameter | Range | Default | What it does |
|---|---|---|---|
| Flange width | 120–400 mm | 230 mm | Across the car. The Fusion original is 400 mm, which exceeds a 256 mm print bed; 230 mm fits one. |
| Flange length | 120–340 mm | 200 mm | Fore and aft, in the flow direction. The cowl exhausts over the trailing edge, so this is also how far forward of the exit the flange reaches. The Fusion original is 310 mm. |
| Flange thickness | 4.5–10 mm | 5 mm | Has to be thicker than the countersink is deep, so larger fasteners need a thicker flange. The Fusion original is 5 mm. |
| Corner radius | 3–60 mm | 25 mm | The Fusion original is R25. Generous radii stop the corners lifting and peeling at speed. |
Cowl
| Parameter | Range | Default | What it does |
|---|---|---|---|
| Cowl height | 20–110 mm | 42 mm | Peak of the cowl above the flange's top face, measured at the exit. The Fusion original is 64 mm on a 310 mm flange. |
| Cowl width | 60–320 mm | 170 mm | Width of the cowl where it meets the flange at its nose, its widest point. The cowl narrows by 17% from here to the exit, as the original does. Must leave room for the side fastener rows. |
| Cowl length | 60–300 mm | 150 mm | From the cowl's nose back to the flange's trailing edge. A longer cowl is a shallower ramp, which stays attached better; a short one has to be low to match. |
| Wall thickness | 1.6–6 mm | 3 mm | Shell thickness of the cowl, measured normal to its surface. The Fusion original tapers from about 5 mm at the base to 3 mm at the exit; this one is constant. |
Fasteners
| Parameter | Range | Default | What it does |
|---|---|---|---|
| Fastener size | M4 countersunk · M5 countersunk · M6 countersunk · M8 countersunk | M6 countersunk | Heads countersink into the underside so they finish flush with the airflow. Holes are ISO 273 normal-fit clearance. Hole count and spacing are derived from the flange size at a maximum 60 mm side pitch and 160 mm leading-edge pitch, matching the original's 13-hole pattern. |