Intake restrictor / insert / reducer / delete from air box

[2016 4Runner SR5]

I made a post in the "what did you do to/in your 5th gen today" thread which seemed to get a lot of attention so I figure it would be a good idea to make a dedicated post about it.

So I was seeing a bunch of people post stuff about a restrictor in the stock air box which was noticed when replacing with an aftermarket intake. I figured there had to be a way to remove it so I messed around with it tonight after work. Removed the lower air box, removed the water shield from the intake box, tapped the restrictor from the inside once with a hammer, fell right out. May have improved midrange power and it has a subtle throaty sound to it now. Not the sound of an aftermarket intake by any means but I do hear a difference. Only other mod is an AFE Pro Dry drop in filter. 10 minutes and free, works for me!

 

[Rightside Up]

Nice. May try.

 

[Eitek1]

May be a helmholtz resonator. You ever ride around in some cars and roll down the window and hear a pulsating noise?

It's because of a pressure pulsation. Sometimes rolling down another window eliminates it. When it happens in your air intake it's counter productive and could be the source of your "throaty" sound. That plastic piece may have been there to eliminate the pulsation.

Or... it's there to decrease the air and stifle the engine for some reason.

 

[wfo9]

I have no idea what you guys are talking about..A restriction? Take the airboxes out a few times. Nothing like that I have ever seen but maybe they were already removed... Odd

Edit.. it is in mine, but that is not a restriction of any type LOL. It's just the inlet trying to keep the dirty air spread across the filter media vs on one spot. Will make no difference in performance IMHO. I would leave it in there.

 

[WallyT4R]

Also posted this question in the other thread before seeing you made a separate thread....Why is that "restrictor" in there? Is it possibly for protection from water infiltration into the air intake? I mean why else would they put something like that into the air intake, anyone???:noidea:

And does the TRD intake have a "restrictor"??

EDIT: Ok maybe I'm being dense here, that happens from time to time...what exactly came out of there? That small looking tube to the right of the airbox in your first pic?

 

[epjfsa]

May be a helmholtz resonator. You ever ride around in some cars and roll down the window and hear a pulsating noise?

It's because of a pressure pulsation. Sometimes rolling down another window eliminates it. When it happens in your air intake it's counter productive and could be the source of your "throaty" sound. That plastic piece may have been there to eliminate the pulsation.

Or... it's there to decrease the air and stifle the engine for some reason.

That's almost certainly what it is, and OP likely lost power as a result. It's very easy for the butt dyno to be fooled by a change to intake sound - it's why "cold" air intakes sell

 

[Bodhi327]

I just pulled my stock air box on a 2016

I did not have the same set up with that part you are labeling a restrictor. The stock intake has the shovel looking thing, the Trd intake has something similar to that but shorted and it’s rubber not plastic.

 

[TRUSTYAXE]

I have no idea what you guys are talking about..A restriction? Take the airboxes out a few times. Nothing like that I have ever seen but maybe they were already removed... Odd

The black "nozzle in the pics above, already separated from the lower air box.

Also posted this question in the other thread before seeing you made a separate thread....Why is that "restrictor" in there? Is it possibly for protection from water infiltration into the air intake? I mean why else would they put something like that into the air intake, anyone???:noidea:

And does the TRD intake have a "restrictor"??

EDIT: Ok maybe I'm being dense here, that happens from time to time...what exactly came out of there? That small looking tube to the right of the airbox in your first pic?

Here are some theories,

Its a nozzle, designed to improve flow like the tip of a drinking fountain etc.

Its a choke, to meter the air flow in the final design process for mpg's or something. Perhaps a FED gov requirement. They wouldn't have to redesign the whole air box just swap this "insert". Perhaps size matched to the throttle body or something.

All WAG's but I can confirm the truck gets more air, can't say I've noticed any noise but I haven't wound it out either.

 

[TRUSTYAXE]

I did not have the same set up with that part you are labeling a restrictor.

Interesting, what does the lower portion of your air box look like. Pic?

 

[1000MPH]

I asked in the other thread too. Was wondering if its function was similar to the intake resonators. My bone stock engine howls at certain high rpms I think it’s around 3k. I might do some experiments as well.

 

[e60ral]

if i remember correctly from engine design, acoustic tuning is generally for top speed or power conditions so congratulations OP, you slightly reduced your top end performance!

looking at the design of this, in simple terms i believe this "restrictor" sticks in so the differentials from the pressure wave can go beside it instead of continuing back out the intake thus making it harder for air to come in so the box works as the resonator instead of having a seperate tee somewhere along the intake

also if i remember correctly from that class, this applies to a pretty narrow RPM range and improving it for one range can potentially make it worse for another, however since efficiency is very important for a manufacturer their tuning is probably better overall than with this removed even if removing it does help in a different RPM range (which isn't guaranteed).

 

[Antman]

Airbox Chop
I chopped mine up soon as I got it lol

It's been through mud pits, deep water, snow, dusty trails for miles with no issues. I like the sound when I get on it.

I also cut out the charcoal filter in the box. 140,000 miles.

 

[1jzgte]

I did not have the same set up with that part you are labeling a restrictor. The stock intake has the shovel looking thing, the Trd intake has something similar to that but shorted and it’s rubber not plastic.

The TRD part that you speak of is a flared port like so. My guess its to smooth out turbulent air flow which gives the TRD intake a cool swishing suction sound rather than a farting sound.

The shovel looking thing is a water guard. I don't understand how it works or how well it works but that's what it is.

Lots of guys from the nissan titan forum have performed a similar mod

If you look at the nissan filter, you can see lots of dirt concentrated in one spot. In theory and practice, removal of the pipe helped evenly-er distribute dirt on the entire surface of the media. However will be more turbulent and become noisier. As discussed in the link below:

DIY - Air Box Mod - Nissan Titan Forum

 

[wfo9]

90% sure the part the OP is talking about is not on all years. Never seen it myself. Also. look at the ARB installation instructions.. no mention of it and that does require modification of the airbox inlet.

http://www.toyota-4runner.org/attac...874889-safari-snorkel-5th-gen-new-ss450hp.pdf

It should make no difference whatsoever besides sound.

 

[1jzgte]

if i remember correctly from engine design, acoustic tuning is generally for top speed or power conditions so congratulations OP, you slightly reduced your top end performance!

looking at the design of this, in simple terms i believe this "restrictor" sticks in so the differentials from the pressure wave can go beside it instead of continuing back out the intake thus making it harder for air to come in so the box works as the resonator instead of having a seperate tee somewhere along the intake

also if i remember correctly from that class, this applies to a pretty narrow RPM range and improving it for one range can potentially make it worse for another, however since efficiency is very important for a manufacturer their tuning is probably better overall than with this removed even if removing it does help in a different RPM range (which isn't guaranteed).

How do you explain the engineering behind the TRD intake? It has no "restrictor" nor any helmholtz resonators. I agree with you to an extent but I don't think this mod is as harmful to the power band as made out.

My experience with this mod has been fairly positive. Butt dyno claims slightly more mid range. I don't spend enough time in the upper RPM range to know whether I've lost any power. Most importantly, mpg has remained the same. I was hoping for mpg improvement but was satisfied that I didnt lose any mpg.

The mod is simple enough to revese so just try it.

 

[wfo9]

I finally see what the OP was talkilng about. The term restrictor really threw me off.

The purpose of it is more about capturing dirt in the box and prolonging filter life than anything else.

Should make no difference either way really. I would leave it in there.. but whatever floats your boat.

 

[spetka]

Kind of reminds me of this Popular Mechanics article I found when someone was trying to talk me into buying one of those vortex devices. Popular Mechanics actually dyno'ed them all.
Looking For A Miracle: We Test Automotive 'Fuel Savers'

Butt dyno is definitely influenced by sound. My old Honda accord with 105 HP felt twice as fast when I put the CAI on it. And my gas milage was cut in half since I just stomped on the gas everywhere to hear the CAI

 

[1jzgte]

I finally see what the OP was talkilng about. The term restrictor really threw me off.

The purpose of it is more about capturing dirt in the box and prolonging filter life than anything else.

Should make no difference either way really. I would leave it in there.. but whatever floats your boat.

yea i wouldnt call it a restrictor either, more like a diverter

 

[TRUSTYAXE]

I finally see what the OP was talkilng about. The term restrictor really threw me off.

The purpose of it is more about capturing dirt in the box and prolonging filter life than anything else.

Should make no difference either way really. I would leave it in there.. but whatever floats your boat.

yea i wouldnt call it a restrictor either, more like a diverter

I think the term restrictor came along after it was determined that once removed, the truck got more air. My truck reacted to it upon first start the next morning. So nozzle, diverter, restrictor, call it whatever you want. It restricts air flow.

Now at high rpm, does it cause some sort of turbulence that others have mentioned, "effectively reducing performance" at high rpm's? Dunno, but I do know my truck rarely gets into high rpms.

 

[e60ral]

How do you explain the engineering behind the TRD intake? It has no "restrictor" nor any helmholtz resonators. I agree with you to an extent but I don't think this mod is as harmful to the power band as made out.

My experience with this mod has been fairly positive. Butt dyno claims slightly more mid range. I don't spend enough time in the upper RPM range to know whether I've lost any power. Most importantly, mpg has remained the same. I was hoping for mpg improvement but was satisfied that I didnt lose any mpg.

The mod is simple enough to revese so just try it.

i'm not positive because i still can't tell which part they are talking about exactly. the baffle is probably for dirt/water. the TRD part is probably designed for consumer preference.