Toyota 4Runner Topsites

Jason's 4Runner Limited - Deck Plate (Airbox mod) If you don't already know, I have an accessory site and sell wood dash kits, real carbon fiber/synthetic carbon fiber dash kits, euro clear lenses, etc, for 4Runners.  Better yet, look at the link below.

There are a few ways to get more air flow in your truck. Some people have done their own testing, and have found that the K&N open air intake shows a decrease in HP. This is only when the setup is used in the 4Runner or Tacoma . This is why I've stayed away from this setup. The other way is to remove the airbox elbow that goes into the fender. I didn't want to do this, in fear that water could be sucked into the filter with no way to stop it. The only other way would be to remove and reinstall the elbow. I also wanted a simple way to revert back to the stock performance configuration. This is why I liked the idea of the deck plate. I have never removed the elbow prior to this mod and it is still in place. I've also had the Amsoil filter in place for about a year.

This mod  involves cutting a 4.25" hole in the front of your stock airbox. A lot of Tacoma owners started doing this modification and the word is spreading. I found the instructions from this page, (thanks to Bratik and Tacoma Territory) You will see that some info was copied & pasted.

A 4 inch deck plate can be found at any marine/boat store and they run around $10, (the plate and cover). A deck plate is typically used as a cover that will not open that gives a complete watertight/airtight seal. More info on deck plates and what they do.



Above you see the stock airbox before removal.  To remove: Take off the three bolts holding the air box in place. Use a ratchet with a long attachment. This will make it easier to get the bolts out. Remove the big round air tube. Loosen the clamp using a phillips screwdriver and then carefully unplug the sensor on the right. Now remove the tube from the box. Next remove the smaller tube to the right by grasping the metal ends to loosen. Now you are ready to remove the whole air box. You may have to jiggle it a bit to get the side elbow (on the left) to come out. After you pull the box out, it would be a good idea to remove the Mass Airflow Sensor. It's attached with two bolts to the end of your airbox. This is a very delicate/sensitve component which costs hundreds to replace if damaged. After you remove the sensor, cover both ends with some duck tape to keep the dust out.

Next pull the EFI fuse from the fuse box in the right side of the engine compartment and leave it for now. Pull the small 15 amp one - not the big one. This will reset your EFI computer so it will relearn your air intake settings. Be sure to replace the fuse when finished with this mod. 

Warning: After the fuse is reinstalled, your shifting patterns will be a little screwy until the ECU learns to accommodate for the new amount of airflow. It usually takes about one tank of gas to adjust completely.  You should do this after any mod that will affect performance.

Above you see the stock air box removed, with a 4"  inch  pencil template. 

Luckily, I had access to a 4.25" hole saw, a tad bigger than the pencil template above.  For this reason, no filing or trimming was needed for the deck plate to fit in place. This made the cutting a cinch! It took about 10 seconds and it was done.  You could also use a Dremel, but it will take much longer.  Cutting through the waffle style backing will take some time. If you use a Dremel, take your time. I also lined the inside of the box with saran wrap. This will keep all the plastic shavings from getting into the airbox.  Plastic shavings in your engine is the last thing you want.

Here is the outer ring of the deck plate with the clear cap in place. My deck plate came in white, but I decided to paint the outer ring gloss black to compliment the airbox.

Next you need to mark the holes where your screws will go. Dry fit the ring in the hole. I used a pencil to mark the box. Now you can pre-drill the holes using a small drill bit. You will need 6, #8 stainless steal screws ($1) from your local hardware store. I painted the tips with a black paint marker to finish them off.  Before you put the ring back in place and put your screws in, put a bead of acrylic adhesive on the inside of the ring. This will give an air tight/water tight seal when the cap in screwed in place.

Above you can see the deck plate with the Amsoil air filter lurking in the background.

Above, the clear cap can be seen screwed in. You will only need the cap in place when offroading or coming in contact with high waters.  The cap also makes an easy way to dyno test this mod. Cap on, cap off, which take about 5 seconds. From what I hear, this mod adds about 7 HP on the dyno powered from a naturally aspirated Tacoma. The Tacoma uses the same 3.4 liter engine as the 4Runner. Remember, when the dyno is done the truck is at a standstill. When moving, the warm engine bay will be flushed with cooler air. The cool air from under the headlights and front grille should give even better results.

Above is the airbox reinstalled with clear cap off, for performance driving!

Above is the airbox reinstalled with clear cap on, for the offroad at heart!

I took a short drive after the install and did "notice" a power increase at about 3,300 rpm before it shifts into 2nd. Also at about 25-45mph, but I didn't get on the highway yet. 

On the second test, I had three people in the truck.  It seems I can feel the power even more, especially when first staring out from a stop. 

The only noticeable difference in sound is at W.O.T. (Wide open throttle) You do hear more of a roar -- the scream of a lion that wants out of its cage.  It's by no means overbearing.

The shifting patterns are still adjusting due to the removal of the EFI fuse. I will have more to report later...

site created by Jason Burtman (WebMaster)