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Automotive Tech

Bumper Cover and Resonator Removal ('99 Si/SiR)

Removing the resonator from your stock airbox will allow it to breathe a bit easier, and will make for a much louder intake noise under load and WOT (wide open throttle). This modification will NOT make the engine significantly more powerful. As well, it will expose your airbox opening to a bit more debris and water than the stock setup does. At this point I have not heard of anyone having a serious problem with this modification, but it will likely mean replacing (with stock filters) or cleaning (with washable aftermarket filters) your filter more often.

Resonator removal is a necessary procedure when installing an aftermarket "cold air" style intake. Resonator removal is not necessary when installing an aftermarket "underhood" style intake, unless a cold air feed from the front bumper area is desired.

The procedure listed below includes removing the front bumper cover. Some have mentioned that the resonator can be removed through the passenger side fenderwell, but I find it much easier to do it with the bumper cover off. As you will see, bumper cover removal is not terribly difficult.

Note: The usual disclaimers about safety and responsibility apply here. This procedure may lead to undue wear and tear or damage to your engine. This procedure is to be done at your own risk.

Bumper cover removal:

    Pic: Fender Bolt Location
  • Open the hood and remove the pop-up fasteners from along the top of the grille. This is easiest with a small screwdriver. Pop up the middle of the fastener with the screwdriver, then pull both pieces out. Do not forget the two on the very sides that sit a bit lower than the rest. Do not lose any of these as they come off in two pieces and are lightweight.
  • Unsecrew the four bolts that hold the bottom of the bumper cover in place. These are located aft of the bottom lip, two with phillips heads towards the outside, and two with 10mm socket heads closer in. Make sure to distinguish these from the bolts that hold the Si/SiR specific front lip in place. The front lip comes off with the bumper cover, so it can stay attatched.
  • Unscrew the two bolts on either side of the car located in the fenderwell. They are located on the leading edge of the fenderwell and screw upwards (arrow in picture) just behind the lip of the bumper cover. Once these two bolts are removed, each side can be unhooked by gently pulling downward and outward right where the last two bolts were removed.
  • Once both sides are unhooked, the bumper cover can be pulled away by lifting and pulling from the middle of the grille.
  • Place on a clean, soft surface (carpet, grass) to ensure the cover is not scratched.

Airbox removal:

  • The resonator and intake piping is much easier to remove if the airbox is removed first. Unhook the radiator overflow reservoir by sliding it upward from its mount. It can be placed on the header without disconnecting it from the radiator (just be sure the header is not hot and be sure to put it back in its place when done or it WILL be melted once the car is started).
  • Undo the two bolts that bolt the airbox to the shock tower. When reinstalling these, be careful not to cross thread them.
  • Undo the intake piping downstream (leading to the engine) of the airbox by squeezing the tube and working it off.
  • There is one more rubber mount holding the airbox down. The airbox can be gently but firmly popped off of this rubber mount. Be careful, as some have broken the tab off of the airbox when doing this step.
  • Make sure no debris goes into the airbox or the intake tube that leads to the engine, as this debris will be sucked up by the engine at startup and may cause undue wear or damage. A clean rag can be stuffed into both openings to prevent this from happening.
  • The opening in the bottom of the airbox will have a rubber adaptor in it that mates the intake tubing to the airbox. This can be removed.

Resonator and intake tubing removal:

    Pic: Resonator
  • The resonator is held in place by three bolts indicated by the red arrows. The arrows show the direction in which the bolts screw in. Undo all three bolts at this time.
  • The yellow arrow indicates the bolt that holds the resonator to the intake piping. Remove this bolt and pull the resonator off of the intake piping.
  • At this point it is a matter of wrestling the intake piping out. Removing the rubber bushings from the right most bolt (in this picture) can help in getting the resonator past some of the tubing in the engine bay. I found that pushing down on the tube from inside the engine bay works best use force but be sure not to damage anything in there!
  • At this point some dryer hose or pvc tubing can be fabricated to supply the airbox opening with cool air, or, in the case of installing an aftermarket system, the new filter and tubing can be installed now.

Airbox reinstallation:

  • Remove any clean rags used to prevent debris from entering the airbox or tubing
  • Place the airbox into position and work the intake tubing back onto the airbox. Make sure that the U shaped tab on the intake tubing butts right up against the tab on the airbox, and that the tube is evenly on all the way around. Any leaks here will allow unfiltered air into the engine.
  • At this point the airbox needs to be pushed back onto the rubber mount at the bottom of the front. This can be done by applying downward force and working the box back and fourth until the rubber mount pops back in place.
  • Reinstall the two bolts holding the airbox to the shock tower. Again, be careful not to cross thread these if any resistance is felt when first screwing them on by hand, back them out and try again until no resistance is felt.
  • Replace the radiator overflow reservoir.

Bumper cover reinstallation:

  • Carefully lift the bumper cover into place holding it from the middle. At first it can be rested in place in its approximate position until the sides can be popped back into place.
  • Go to each side and push the bumper into place where the side bolts will eventually hold it in place.
  • Underneath, along the edge of the lower lip and to the sides, are two tabs that help hold the lower part in place. Make sure the lower part of the bumper engages these two tabs.
  • Gently push the cover into place and replace the pop up fasteners along the top of the grille.
  • Replace the bolts on either side at the fenderwell. The bumper cover has a hole at this point that engages a white colored flange that points downward. If the hole does not engage the flange, the bumper cover will not butt up against the fender properly if there is too much space, make sure the hole is lined up with the flange.
  • Replace the four bolts along the bottom of the bumper cover.