The info below will be broken up in to two pages.
Page one here will be the info for '99 to '02 rigs, while page two will deal with '96 to '98 rigs.
There is a difference in the methodology on how to do this mod between the years.
10/18/2002

This article details an inexpensive way to get some more Horsepower and Torque out of a 99-02 4Runner with the 5VZ-FE engine by making a modification to the intake system. If you own one of these trucks, this article will be of interest to you. There will be a companion article for the 96-98 4Runners as well, but we are still working on that particular truck because the intake system is different. Before we get into this modification, I'd like to give a bit of background on myself.

I am 38 years old and I live in the Portland, OR metropolitan area. I repair computers for a living. I used to wrench on cars for a living, and I even went to school in the Bay Area of California at a place called Sequoia Institute for Automotive Mechanics. After doing that for a few years, I found that I didn't want to work on cars to support myself, but I still enjoyed fixing my own car; and friend's vehicles on occasion. I don't know everything there is to know about engines, but I'm not new to an engine bay either. I've owned several Toyotas, 4 to be exact. I currently own a 2000 4Runner SR5 V6 with a 5 speed manual transmission. I bought it used from a Toyota dealership in December 2001. It had just under 34,000 miles on it. It was immaculate.

My last vehicle was a highly modified 1987 Supra Turbo with a Dyno-tested 355 RWHP. It was an extremely powerful car and very, very fast. All of the performance components that were installed on that vehicle were basically bolt-ons, with a few exceptions. I had to get rid of it because I had cracked the rear sub-frame section that holds the rear suspension together and to the rest of the car. I shouldn't say cracked, I severed the sub-frame in half actually. This is rather common in these cars when you add over 150HP to them. The rear end just torques itself apart. I had welded some plate steel to it at one point when it had weakened, and drove it that way for quite a while. But it came apart during some “hard use”. I just didn't have the heart to put any more money into it. So, I sold it to a wrecking yard.

Moving from that car to the 4Runner was quite a leap. The amount of power that it came with was a bit lacking, for me. So, I set out to get a bit more oomph out of it. This article is about my latest mod. It's easily one of the most cost effective performance enhancements I've made to it or any of my other vehicles for that matter. I first posted this in a 4Runner forum. It has since been edited a bit. Here it is:

Here's what we're removing:

Here's a picture of the intake system taken apart: (Thanks goes to JA for this pic.)

Every vehicle I've owned has had its stock intake system replaced or modified by me for better performance. In every instance, I've been successful. My reasoning for believing that removing this component will help is this: It takes time to fill that chamber with air. The air coming into the engine is not a constant stream. It is pulsing with engine RPM’s and the load placed on the engine. Inside the Silencer is a “slot” which traps the intake pulses acoustically and filters out the low frequency, large amplitude pulses. I believe the silencer reduces the maximum velocity that the air can achieve entering the intake polonium.

Here's a pic of the Slot inside that tunes out the pulses:

Air in motion is cooler in temperature than still air. Air of a higher velocity has even more of a cooling effect. I think everyone reading this knows about “Wind Chill Factor” and the effect of a cooling breeze on a warm day. Cooler air is also denser and it contains more oxygen. By increasing the velocity of air entering the engine, the air is cooler and more oxygen rich. The intake system contains an IAT (Intake Air Temperature) Sensor which tells the engines ECU what the temperature is of the air entering the engine. When the air is cooler, the ECU can run more aggressive timing curves which result in better performance. You ever notice how “peppy” your engine is in the morning when you first fire it up? This same cooling effect is the reason behind why the DeckPlate mod works. A larger amount of air, moving at a higher velocity, and therefore cooler air, is entering the engine with the DeckPlate off versus a stock airbox.

There have been some counter-points to this line of reasoning brought to my attention. Here is a link to some excellent articles on the subject. You can draw your own conclusions. I just wanted to make sure you had both sides of thought about this. I will say this about those articles; every engine is different, so not all of that information and testing in those articles applies to every engine. They're still worth reading all the same. Part of this counter-point is that if anything, removing the Silencer will change the torque curve and cause a loss of low-end torque. That has not been my experience. Read on.

I was speaking with Loosehead, another forum member about this mod before doing it. He has a 1998 4Runner with the 5VZ-FE in it. The intake plumbing is a bit different on the 96-98. He's the guinea pig for the 96-98 models. Anyway, I had taken measurements and knew the size of pipe needed, but I was having trouble tracking down the appropriate size. I wanted to use ABS or PVC, but no one had any that was the right size. Loosehead suggested I talk to a muffler shop. Great idea! I called a local shop, Master Muffler. They have several locations in the Portland, OR area. I told George on the phone what I was trying to accomplish. He was very helpful and even gave me ID and OD diameters for the various pipes he had in stock. None of what he carried was the correct size, either. However, he said we could expand the pipe to the right size. He told me to come on down and see what we could do. (I knew I had talked to the right shop.)

When I got there, we removed the Silencer to take some final measurements. We used 2.5" OD 14G pipe and expanded it on the pipe bending machine to the correct diameter and cut it to length. Then we cleaned up the burrs and brushed out all the stray pieces of metal.

Here are the dimensions needed for the piece of piping to replace the Silencer box:

Length - 5.625"
Diameter - ID - 2.5"
Diameter - OD - 2.625" ~ 2.75” (Larger than 2.75” OD will be a tight squeeze.)
Pipe is 14G Mild Steel.

George was awesome. He spent about 30 minutes with me working on this. I asked him how much for the pipe. "5 dollars." was his answer... I couldn't believe it either. Like I said, I knew I went to the right place. I gave him $6 because that's how many "ones" were in my pocket. I'm a big spender.

Here's what it looks like installed:

Here's another shot:

A close-up: (You can see my Magnacor wires in this one.)

After talking about this with some folks on the forum, I decided to get the pipe powder-coated so that it wouldn't rust. I think it gives the install an OEM appearance.

Okay, now that the pipe was installed, I needed to put the FPR hose somewhere since I lost the nipple on the Silencer. On the front of the intake plenum is a nipple with a small hose coming off of it. I purchased a ¼” Plastic Tee and about a foot of 7/32” hose. I cut a short piece about 2” long to attach the Tee to the nipple on the plenum. I attached the hose that was formerly on the plenum to the right side of the Tee and attached a 6” piece of 7/32” hose to the left side of the Tee and the other end of it to the FPR Tubing that runs under the plenum to the FPR.

Here's a pic:

I also purchased a new hose for the EVAP system. It's the hose that runs across the engine bay and attaches to the Airbox just Upstream of the MAF. It's stiffer than the stock hose and it doesn't “droop” onto the engine. The stock hose drooped when I removed the Silencer. I think this looks much better.

Here's a pic:

Total cost for Tee & Hose:   $5.78
Total Cost of Pipe:     $6.00
Total Cost for Powder Coating:  $20.00

Total cost of Mod:  $31.78

Okay, so now that this is all done, what did I notice?

Off the line and all the way through redline there is a noticeable difference in the engine's performance. It's more than I expected it to be. I think my estimate of 5-7 RWHP was a bit low. Acceleration at all speeds is improved. Throttle response is punchier and more immediate. Not only that, but the Intake Growl sounds awesome. It even beefed up the exhaust note. It's pretty Hot-Rod sounding. Of course, this could all be in my head, but I'm intimately familiar with the way my truck runs and sounds. Also, I was running a tank of Mid-Grade Octane to see if I noticed a difference and with the stock intake, I couldn't tell. With this new intake setup, I could induce pinging, which to me is a good thing because it means that the Ignition Timing is more aggressive and more air is entering the engine. It was back to Premium gas for me. This might have been caused by winter blend gas, but there was a difference. A tank full of premium gas ceased all pinging, by the way.

One other thing I noticed as I got to drive it a bit more and with more time on the freeway: The exhaust note at cruise is even quieter now. It's as if the engine had to "labor" more before to sustain the same speed than it does now. It's almost silent. When you get on it however, it has more of a growl than before, which to me is the best of both worlds. Quiet at cruise, but wakes up and announces it's presence with authority when you want it to.

After driving it around for about a week, I decided to install the DeckPlate mod to see if there would be a difference. Oh. My. God. I hate to sound like I'm making things up or exaggerating, but you gotta do this mod with the DeckPlate. I previously had been running with the Elbow removed because I didn't want to punch any holes in my shiny new truck. But now that I've got a few "unexpected modifications" from playing and other stupid stuff, I thought, "What the hell?" Again, I was not prepared for the amount of power gain from these two simple mods.

There is so much more power (at all RPMs) "On Tap", than before. It's amazing. The midrange especially is a godsend. Also, the engine "spools" much more quickly. So quickly in fact, that it makes me wish there was a bit more headroom before Redline. Another 500-800 RPMs up top would be really nice. Larger Cams will probably help with that. EL Prototypes is milling cams for these engines now, in case you weren't aware.

A caveat: If you do this mod in combination with the DeckPlate mod, the intake noise at large or wide open throttle settings is much, much louder than with the Silencer in place. It's similar to a large 4-Barrel Carbureted V8 with an Open-Element filter on top. It's very deep and throaty. I personally love that sound, but some may not. At lower throttle settings and at cruise, you can't tell a difference. If you do the Elbow mod in concert with this mod, it's not too bad.

Speaking of the Elbow mod in combination with this mod… It is my experience that the combination of the Elbow Removal mod with the Silencer Removal mod yields more power than the DeckPlate mod alone. This is just an FYI.

Another counter-point some people have made about all of this is that I'm “Fooled” into believing the engine has more power simply because it is louder. That would be true were I a fool. However, I am not. All my other senses do not stop working because my ears hear a loud noise coming from my engine. My eyes still notice how much more quickly my engine revs by looking at the Tachometer. My body still notices how much more quickly my truck accelerates and how much harder it pushes me back into the seat with the mod than without it.

Please take this article for what it's worth: My opinion and experience. I would never do something that I thought was going to harm my engine or give it worse performance. I certainly wouldn't recommend that other people to do the same. I am confident that this mod is worthwhile and that it adds a measurable amount of HP and Torque. People have requested that I Dyno test this mod. That will happen in the near future. Please check back for the results.

I am going to make some videos that will show how my truck performs in some “rolling acceleration” tests with and without the mod in place. I am confident that the videos will speak for themselves. Please check back for those really soon.

So, there you have it. If you own a 96-98 V6 4Runner, please wait for the companion article. I Hope this is helpful. If anyone tries this, please post back with your results. Also, if you have any questions, well, I'm sure you guys will ask.  :D

If you want to email me, you can reach me here
Peace!
Dr. Z

If you choose to do this mod good luck and if you have any questions  (Dr. Zhivago) on the Yotatech Forum.

Please click here for the info on '96 to '98 rigs.
New information has been brought up on doing this to the 2002 3.4 engines. Please click here for more info.