Honda Fit (GD): Injen Cold Air Intake Installation
Introduction
This guide covers fitting an Injen cold air intake to the first-generation Honda Fit (GD). The Injen kit is a convertible design that can be run as a full-length cold air setup, with the filter tucked low behind the front wheel arch for cooler intake air, or reassembled as a short ram unit. On the Fit the cold air routing requires the front bumper cover to come off and a small section of wheel-well liner to be trimmed, which makes this more involved than a typical bolt-on filter. Owners running the intake report a slightly leaner air/fuel trim, consistent with the extra airflow, and the kit is CARB exempt in both configurations. This procedure applies to the Fit's 1.5-litre L15A engine in the GD chassis. Adapted from a community writeup by dmxsoulja3 on FitFreak (https://www.fitfreak.net/forums/fit-engine-modifications-motor-swaps-ecu-tuning/8460-diy-installing-injen-cai.html), including corrections from the follow-up discussion.
Reference
Tools Required
- Socket and ratchet set
- Combination wrenches
- Phillips and flat screwdrivers
- Trim/panel clip removal tool
- Pliers
- Dremel or rotary cutting tool
Parts Required
-
Injen cold air intake kit for the Honda Fit (intake pipes, silicone couplers, hose clamps, air filter)
-
Vibra-mount isolator bracket (supplied with the kit)
Safety Warnings
- ⚠ Hydrolock risk is set by the height of the open pipe end, not by how high the filter sits. Once standing water reaches the level of the pipe it can be drawn into the engine and destroy it, so avoid deep water regardless of filter position.
- ⚠ Disconnect the negative battery cable before beginning work under the hood.
- ⚠ Cutting the wheel-well liner is permanent; measure and test-fit before removing any material.
Step-by-Step Instructions
1 Disconnect the battery
Before removing anything under the hood, loosen the clamp on the negative battery terminal and lift the cable clear of the post. Tuck it aside so it cannot spring back onto the terminal while you work. This removes the risk of an accidental short during the install and lets you cycle the engine's air/fuel learning once everything is reconnected.
2 Remove the factory airbox
The stock intake assembly is held by roughly two mounting bolts plus a small number of hose clamps and connectors. Loosen the clamps, unplug any sensor or breather connections, back out the bolts, and lift the airbox and its intake tube out of the engine bay. Keep the fasteners together in case you ever want to refit the original box, which can be reinstalled in about ten minutes.
3 Remove the front bumper cover
Cold air routing runs the filter down behind the wheel arch, so the front bumper cover must come off. Release the row of plastic push clips along the top edge under the hood (about four), then remove the screws inside each front wheel arch (roughly two per side) and the screws and clips along the lower edge of the bumper. With the fasteners out, free the side tabs where the cover clips to the fenders and unhook it from beneath the headlights, then draw the cover forward and off. Treat the counts as a guide and confirm each fastener visually before pulling.
4 Choose the intake configuration
The Injen kit can be built as either a full cold air intake or a short ram. For the short ram path, stop after the airbox is out and assemble the pipework in the engine bay. For the cold air path, continue with the lower pipe routing below. Decide before assembling couplers, since the two layouts use the sections differently.
5 Assemble the upper pipe section
Following the kit's own instructions, fit the silicone couplers, clamps, and the first short length of pipe at the throttle-body end. Leave the clamps only lightly snugged at this stage so the assembly can still be rotated and shifted once the lower section is joined to it.
6 Trim the wheel-well liner
The kit instructions call for a small notch to be cut in the plastic underliner so the intake piping can pass through cleanly. Mark the area against the pipe path, then remove only the minimum material with a Dremel or rotary tool. Test-fit before enlarging the cut, since the trim is permanent. Deburr the cut edge so it does not chafe the pipe.
7 Relocate the ground wire
A factory ground strap sits where the intake needs to run. Undo the body-colour bolt securing it and move the ground to its new location per the kit, then reinstall the bolt. This frees the original mounting point for the intake's isolator bracket in the next step.
8 Route the lower pipe and mount the filter
Feed the second, longer pipe up from underneath the car toward the top of the engine bay rather than pushing it down from above, which scratches the finish. Seat the Vibra-mount isolator bracket at the point vacated by the relocated ground so the pipe is supported, and position the filter down behind the wheel arch.
9 Join the sections and align the intake
Connect the upper and lower pipes at the coupler, leaving a little gap inside the joint so the two pipes are not forced hard together and cannot bind under engine movement. Shake and reposition the assembly to confirm it clears surrounding components, set its final alignment, then tighten all clamps evenly.
10 Reassemble and test
Refit the front bumper cover by reversing the removal sequence, reconnect the negative battery cable, and confirm every clamp and fastener is tight. Start the engine and let it idle, listening and checking for any intake leaks or loose joints before driving. Re-check the clamps after the first drive as the couplers settle.
Pro Tips
- 💡 Servicing the filter does not require pulling the bumper again. Fold back the front wheel-arch liner, the same access used for changing a headlight bulb, and the filter is reachable from there.
- 💡 The kit is CARB exempt and converts between cold air and short ram layouts, so you can change configuration later without buying different hardware.
- 💡 Expect the air/fuel reading to trend slightly lean after the install, which matches the added airflow; light-footed driving can help fuel economy.
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