Building a Custom Sealed Airbox and Cold-Air Duct for a Short Ram Intake (Honda Accord Euro CL9)

Unbolt and remove the standard airbox and the resonator, then install your short ram intake and pod filter following the relevant kit or removal procedure for the CL9. Confirm the pod sits where you have clearance to build an enclosure around it before committing to any dimensions.

Measure the space surrounding the pod and sketch the enclosure as a set of flat panels: two sides, a top cover, and a lower panel that closes off the space beneath the pod's intake arm. Size that lower panel a little smaller than the piece it tucks against so the two seal cleanly. Redraw each panel full-size on cardboard and cut it out, leaving about a 5mm margin on every edge so you can trim for a tight fit. Test-fit as you go and tape the pieces together with masking tape. Expect to cut a second set of templates; the first usually gets trimmed past the point of fitting well. Note that different pod brands need different box dimensions.

Choose which panels will be riveted into a single unit for better sealing and which stay separate for serviceability. A larger assembly seals well but is harder to fit and remove. A workable split is to join the two side panels into one piece while keeping the top cover and the intake-arm seal as removable parts.

Transfer each cardboard template onto the 1.0mm sheet aluminium with a marker and cut the panels out. The 1.0mm sheet is too heavy for tin snips on tight radii, so rough-cut with the snips and switch to the rotary tool with a cut-off wheel for curved edges and awkward corners. Dry-fit each panel in the engine bay and trim until it seats correctly. Deburr and smooth every cut edge with sandpaper.

Mark rivet positions along the mating edges with a permanent marker. Set each mark with the hole punch and hammer so the drill bit cannot wander on the smooth metal, then drill. Fit the first panel back in the car and use it to mark the matching holes on the panel it joins to, so the holes line up. Join two 1.0mm panels with the 4-1 rivets; step up to the 4-2 rivets wherever the stack is thicker.

To stop the aluminium chafing paint or the stainless intake pipe, slit the 5mm tubing lengthwise with small sharp scissors and press it over the exposed edges, holding it with a light contact glue such as UHU. Where panels grip the intake pipe, size them for a firm friction fit. Then cut a length of the 2-3mm aluminium bar and shape it into a bracket that anchors the top cover to the chassis using the original airbox mounting hole.

Bare aluminium absorbs and re-radiates engine heat into the trapped air, so line the inside faces of the box with the 1.5mm sheet rubber; placing it on the interior means incoming air contacts the cooler rubber rather than heat-soaked metal. Punch, drill and rivet through the rubber, working from one end, and seat a 1/8 inch washer on the rubber side of each rivet so the head cannot pull through. Trim the excess with a sharp knife. Roughly 20cm x 150cm of rubber covers this box with material to spare.

The added rubber thickens the walls, so re-check that the whole box still clears surrounding components and adjust the lid edges until it closes over the insulation. When everything fits, finish the aluminium with high-temperature black engine enamel for corrosion protection and a factory-like appearance, then reassemble.

Feed cool air to the box through the approx. 10cm aluminium ducting pipe run from the front bumper to the base of the airbox cavity. On an 04 base model without foglights, the foglight cover is the entry point; cut openings in it with the rotary tool at a LOW speed, because high speed melts the plastic and it re-fuses. Raise the front of the car and support it on stands, then push the stretched pipe up through the chassis hole from below. Cars with foglights or 06-model front bars need an alternative entry through the front-bar intake or corner cover.

Slip the hose clamp over the pipe before fixing the bumper end. Wrap a band of masking tape around the pipe where a cable tie will pass through, pierce it with a sharp screwdriver, and tie the pipe to the foglight mounting hole; the tape stops the tie cutting into the soft aluminium. Use the nearby headlight ground point and the hose clamp to anchor a thin aluminium tab that holds the pipe to the chassis. At the engine-bay end, relieve the pipe edge so it can fold flat against the chassis. Refit the bumper trim, making sure the lower clips and screws catch the wheel liner as you tighten. Finally, fit a fine metal flyscreen or mesh over the bumper opening to keep insects, bark and road debris out of the filter.