DIY Budget Short Ram Intake for the Honda Fit

Remove the OEM airbox and intake tubing following the standard Fit airbox-removal procedure. Work the intake air temperature (IAT) sensor free from the factory tube gently — do not knock or drop it. Leave the sensor plugged into the harness; disconnecting it is the usual reason a temporary check-engine light appears. Save the rubber o-ring that seals the IAT to the stock tube, since it gets reused in the new elbow.

Fit the 3"-to-2.5" silicone reducer onto the throttle body with the smaller 2.5" end against it. Push it on fully until it sits flush against the locating tab — going all the way here is what gives the IAT wiring enough slack later. Keep the worm-gear clamp loose for now so the assembly can still be turned into position.

Mark a point near the midpoint of the outer curve on a chrome 90-degree elbow. Cut the sensor port with a 5/8" hole saw or drill bit, then clear away every plastic shaving so nothing gets drawn into the engine. Press the o-ring you saved from the factory tube into the new hole; a dab of petroleum jelly in the groove helps it seat and stay put, since the o-rings can be fiddly.

Slide the drilled 90-degree elbow into the 3" side of the reducer. For best results add a second bend so the filter ends up ahead of the battery and out of the radiator's heat path — most owners run two 90-degree elbows, though a 90 paired with a 45 or a 60 also works. To make room, loosen the battery hold-down and shift the battery toward the driver's side, and reposition the radiator hose clamp if needed. Snug the clamps just enough to hold the layout together.

Push the 3" open-element filter onto the free end of the elbow run and secure its clamp. Check that the filter clears the battery and the closed hood, and that its weight is not leaning on anything that could shake it loose — an unsupported filter has been reported to vibrate and fall off. The dual-bend layout generally makes the whole assembly rigid enough to stay quiet.

Insert the IAT sensor into the o-ring until it is fully seated and snug, sitting as square to the tube as you can manage. A sensor that goes in crooked can leak air and dull throttle response, so relieve any wiring tension first — cutting a small semicircular notch at the edge of the coupler, or sliding the clamp slightly inboard, both free up slack. Reconnect the sensor plug if it was ever unplugged.

Slide the small chrome breather filter onto the metal breather tube that used to join the factory intake. Keep in mind this port vents warm crankcase air; if you prefer, run a length of hose from it downward and rearward, below the engine, rather than fitting the filter directly at that spot.

Go around the assembly with a screwdriver and firmly tighten every worm-gear clamp to seal each joint. Drive 50-100 miles, then re-tighten all clamps once the couplers have settled. If a check-engine light appeared from disturbing the IAT, it normally clears itself after several start-and-drive cycles, so no dealer trip is needed. Clean and re-oil the filter periodically per its own kit, and bag it before washing the engine bay.