Bob_98SR5

Intake Silencer Removal Mod
Christian (<96 Runner> on the forums) shows you how he did the infamous ISR mod for his 3rd Gen 4Runner. NOTE: This info is for the years stated above. Please see Dr. Zhivago's ISR write-ups in the Tech Section for other years as well.

Update: Christian has submitted a supplement to go along with this write-up, and it can can found in post #4
-------------------------------------------------------------

Parts Required:
HOME DEPOT
(1) 1.5” NIBCO SCH 40 PVC Cap Part # 447-015
(1) 1” NIBCO SCH 40 PVC Cap Part # 447-010
(1) .5” NIBCO SCH 40 PVC Cap Part # 447-005
(2) ¼” x 1/8” I.D. Hose Barb to MIP adapter Part # A-192B
Flat Black Spray Paint (fast drying)

NAPA Auto Parts (or similar)
(1) 12” L x ¼” vacuum or fuel tubing (match up vacuum line with hose barb)
Napa Part # H-459



Tools Required:
3/8” Ratchet
Extension
10mm socket
Drill with 3/8” bit
Hammer
7/16” Deep Socket (optional, but very helpful)
Supplies
Flat Black Spray Paint
JB Weld

--------------------------------------------------------------
Removing the intake tube and all associated parts
Using a ratchet, extension, and 10mm socket…
Loosen the hose clamps at each end of the intake track.
The first clamp is located at the throttle body.



The second clamp is located by the mass air flow sensor.



Remove everything attached to the intake tube or silencer boxes – this is necessary because the entire intake tube will be coming out. Once everything is clear and removed, remove the intake tube by pulling the end at the throttle body off, then slipping the end at the mass air flow sensor off.



To get a grasp for what we are doing, take each PVC end cap and match it up with its new home on the intake track. Lay out the new vacuum line by the 1.5” PVC end cap (this is where it will be attached later).



Paint the end caps black to match the intake tube.



The caps when finished.



Now, drill two holes using the 3/8” drill bit in the 1.5” end cap.
Hole placement is important. Drill the holes exactly as shown, or the PS vacuum line will not reach.



A vise is very handy.
The 1.5” end cap has a tendency to fly out of your hands when the drill bit catches the PVC.



And the second hole.



Test fit the hose barbs in each hole. This is where the 7/16” deep socket comes in very handy. Because the hose barbs are threaded, screwing them in to the newly drilled hole should be easy. If the hole is not big enough, slightly widen the hole. Repeat as necessary.

Hint: Once the hose barb begins to catch, use the 7/16” deep socket the rest of the way.
When you are confident that both hose barbs will screw in to the end cap with minimal effort, go on to the next step.

continued...

Bob_98SR5

Remove all loose shavings and dirt from the end cap. To ensure a leak free fit, coat the threads of each hose barb with JB Weld.



Once again, screw-in the JB Weld-coated hose barbs. Screw-in all the way till the hose barb bottoms out.



This is what the other side of the end cap should look like once you have threaded the hose barb properly.



The finished 1.5” end cap, with hose barb fittings in place.



The other side of the end cap. Now is a good time to wipe off any dirt or excess JB Weld from the protruding threads.



Moving on to the .5” end cap. This cap is a very tight fit. In fact, the fit is so tight that you will need a hammer to tap it in to place. The original hose clamp is not necessary, but if you desire the added assurance, put the hose clamp on first.



Tap it into place. Be sure to keep tapping until the end cap bottoms out.
Don't worry, there is a lip on the intake track preventing it from going in too far.



The J-pipe silencer end cap is a loose fit. The best way to gauge how far in the 1” cap should go, is by looking inside the intake pipe while moving the cap back and forth.
I found the 1” cap to stick out about .5”. When you are satisfied with the placement, crank down the hose clamp with the 10mm socket.


Note: Our main objective is to streamline airflow, therefore all end cap placement is important. Again, look down the intake track while placing the end caps. Make the fit as flush as possible to the intake walls.

...continued

Bob_98SR5

Now, the most important end cap. The two holes need to be vertical. Again, look down the intake track to check the fit.When satisfied, tighten the hose clamp with the 10mm socket. Re-install the intake tube on the engine.



Hook up the power steering vacuum line to the lower hose barb. The fit should be snug. Use a small hose clamp for added assurance if desired.



Hook up the new 12” FPR (Fuel Pressure Regulator) vacuum line to the top hose barb. Hook the other end of the new FPR vacuum line to the brass FPR fitting under the intake manifold (as shown). Again, use hose clamps if desired.



This is what the 1.5” FPR/PS end cap should look like installed.



Look, no big ugly black silencer boxes!



Pull the 15A EFI fuse for 15 minutes, and plug it back in. While this practice is still up for debate, popular belief is that your ECU will learn the new airflow and adjust quicker than it would if left alone.




Testing:
On a 96 Toyota 4Runner 3.4L 5-speed, with the ISR mod and the deckplate open, the 30 – 70 3rd gear WOT throttle ET dropped .2 seconds when compared to stock.
The ISR mod works.

Notes:
The performance potential of the ISR mod is best realized when used in conjunction with either the deckplate mod, or the elbow mod. If sound is a concern, use the ISR mod in conjunction with the elbow mod. With the deckplate mod open, the ISR mod is extremely (and pleasantly) loud at WOT.

An alternative to hooking up the FPR line as shown, is to cap it off. Testing has shown that this creates a rich condition, mainly because it maximizes the FPR at all RPM. Capping off the FPR created a loss in performance when compared to the line being hooked up. Without proper tuning equipment, the FPR line should remain hooked up (as shown).

Running premium fuel for those at sea level to 4000 ft is also recommended. Some claim to experience pinging while running 87 octane with the ISR mod, and others do not. For those that do not experience pinging while running 87 octane, the knock sensor may be retarding the timing. By running premium fuel at lower elevations, the full potential of the ISR mod is being realized.

END

Bob_98SR5

Christian has submitted a supplement for his ISR mod, and here it is:
---------------------------------------------------------------
Parts Required:
1. 2" radiator hose clamp (instead of the stock clamp) $1.79/pair
2. 2" PVC cleanout plug (from Lowes) $.67
---------------------------------------------------------------


Before painting:

• Drill two holes using a 9/32 bit into the square portion of the end cap (as shown).
• Screw in the barbed hose fittings (test fit). Using a deep socket will make this much easier.
• Remove the hose fittings.
• Paint the cleanout plug if necessary.

After painting:

• Install the barbed hose fittings.
• Install the hose clamp on the intake track.
• Install the new intake plug.
• Tighten the hose clamp.
• Install the PS vacuum line and FPR vacuum line.
• Pull the EFI fuse for 15 minutes, reinstall and drive!

If you choose to do this mod good luck, and if you have any questions (<96 Runner>) on the Yotatech Forum.