Intake flap mod:

Instead of removing the flap as I wanted, I did the mod the way most people have posted about. The vacuum line from the airbox tank goes directly to the valve, bypassing the VSV.

I looped the extra line back to the VSV. In this way the mod is completely reversible for emissions.

The vacuum tank does hold vacuum with the car off, so the flap remains open even while not running.

I should have reset the computer but I have not yet. The soggy area around 2800-3000 is now gone. The intake sound had a noticeable growl even at low RPM. I also removed the lower resonator connected to the intake pipe under the battery which added to the extra noise.

Also, I did remove the charcoal filter from the top of the airbox.

On other cars where I have done a similar mod, the low end torque suffers. The same seems to be true here, going up a hill at less than 2000 rpm it feels like a dog. Of course when the downshift happens it comes back to life.

I feel that a battery reset and switching to 91 octane should be done to take full advantage. If you lookup “3mz intake flap mod” on youtube, you will see the video with sound results.

 

Front air ducting:

The stock air system is very well designed. The air intake duct sucks in air from under the hood gap, so basically a cool air intake, but only when there is enough speed. Also, this area still gets hot. The hood, plastic cover, and radiator support are all hot items, so you are taking air from heat until you get fast enough to take advantage of the front hood gap. Heat soak is not our friend, and it seems like it takes time for the air temp to get cool in stop and go traffic.

I can never leave well enough alone, so I wanted to see if I could grab fresh air from the front grill since it is so wide.

It is important to note that newer models like the Lexus RX350, Lexus ES350 and other newer models have little grill slits in plastic cover near the air intake.

Original setup breathes from over the plastic cover using the hood gap as the air source.

I cut away a piece for the test, folding it down so that it can catch fresher air from the front grill.

A view from the grill shows that now a portion of the air is diverted directly to the air intake. Unfortunately, the horn is in the way of having a more aggressive duct.

After testing, I found that the stock setup was within 9-10 degrees ambient at 40MPH, which is very good. With this partial duct, I was able to get down to with 4 degrees of ambient temperature and at a faster rate.

I will be moving the horn out the way, so that I can make a really nice duct setup. I only do city driving, so with summer approaching I will need every degree of cooler air for my intake.

Also, yes this is completely unnecessary, but it is fun!


UPDATE 4/20:

I moved the drive side horn out of the way (bolted now to the hood latch area), so now there is more room. I made the duct bigger and more aggressive, basically as big as it can be using the stock plastic as a guide.

 

That’s clever!

Sixto
‘04 LE FWD 209K miles

 

As you may have witinessed in the other thread, my intake hose is TOAST. I had planned to replace it anyway with a straight 3" pipe, bypassing the resonator.

Ideally, I would like this pipe to be plastic, just like the TRD intake pipes available for Tacoma, 4runner, and Scion. Since I am in a rush, I am going to just use a single 3" silicon hose from the TB to the airbox. While a polished pipe might look shiny and cool, it will just become a heat sink. Since I am using a straight hose (temporarily), there will be no port for the pcv vent. I am not a fan of shooting the oil vapors on the throttle body, but I do want this modification to be OEM like. This portion is yet to be determined.

Speaking of the throttle body, since we have some downtime, I decided to clean it. Here is how it was to begin with. Not horrible, but there was a decent amount of gunk around the edges of the throttle plate.

With the throttle plate open, you can see the blackness has covered the edges of the throttle plate. Also visible is the intake manifold screen which drives me nuts. Why is it there? Even on Corollas this mystery screen is present. My guess is that it catches some oil so that it is easier to clean than the intake manifold.

After a good dose of carb cleaner and wiping, she is now all clean!

You can also see the coolant lines that run through the throttle body. I will be bypassing this as well when I do remove the throttle body. I do not need 200 degrees of coolant heating up my intake source.


The throttle body and airbox are 3" on each end. This is much larger than what I am used to working with. They are not quite pointing straight towards each other. There is about a 15-20 degree difference in height. I am hoping by having the 3" silicon tube, there will be enough give to not have to modify it.

See you in a couple of days!

 

My silicon intake hose has arrived. I was in a hurry, so I did not find one that has the port for the PCV valve. I hope to find a permanent solution, but this one fits perfectly. No more boxy resonator.

The distance between the TB and airbox is about 9-10 inches.

I can add a PCV port in the intake hose via an add on bung or I might add it to the airbox itself to keep the hose as a single piece.

As I mentioned, I originally wanted a plastic hard pipe, but I am now digging the single hose which would have just 2 clamps instead of 4.

 

I'll be interested to see if any codes pop up as a result of this mod. I've seen people make mods (on other vehicles) out of black PVC pipe to make forced cold-air induction setups and every one of them end up with codes. Usually, they are modifying significantly more, including changing the mounting location of the MAF. One that was particularly sad was a guy who spent a couple thousand dollars on a highly polished stainless forced cold-air intake setup (plus mods and a second version) and, in the end, had to revert back to the factory original version with a simple airbox delete.

BTW, the screen could be there for any number of reasons, however, I saw only video where someone (with a Sienna) went in with stalling and it was found that a mouse had shredded the air filter and paper (from the filter) was clogging up the throttle body. That screen is probably the only thing that saved the engine from death!

 

One of the most common issues when creating a custom intake is that the person would use a 3" maf adapter. The stock MAF tube is not 3", so you are now reading less air and can cause a lean condition. I will be posting later when I test out a 3" cone filter and pipe. Still, I feel that this airbox setup will be more enjoyable and less likely to cause issues.

This project was meant to be just fun and reversable, should you decide to sell the car later. I tried to get as close to possible as what TRD would have offered if they made the same kits they offer for Tacomas and 4runners.

The last pieces of the puzzle arrived today.


K&N style panel washable filter

Resonator and stock hose vs silicon replacement. (The cracked one is missing).

As for the crankcase port, you can find an add on fitting that works with silicon hose. It sort of looks like a valve stem from a tire and bolts in with a nut and washer from inside the hose.

Another option is to have a 3" aluminum pipe with a 15mm fitting, which would allow you to use the stock crank case hose. The original sizes are 12mm (1/2") at the valve cover and 15mm at the intake pipe. You could just leave the resonator there as well, since most argue that it is beneficial to overall performance. In that case, you could just replace the OEM ribbed hose with universal silicon 3" pipe and call it a day.


I was going to add a 1/2" fitting to the plastic part of the airbox for the vent hose, but I want to experiment with a catch can setup, so I will be going that route for now.

Total costs:

$20 3" Silicon hose 12" long (you only need 9")
FREE Charcoal filter removal
FREE Intake flap forced open
$27 Spectre washable air filter HPR9360 https://amzn.to/40ABJ5S