MTL_4runner

No it won't. Driving style affects fuel mileage, airflow does not.

rimpainter.com

Because filtration capability is diminished. The top flap holds in the top of the filter. You run the risk of the engine inhaling harmful particulates with the flap up or off. Also, you lose the ram air effect of the deckplate, albeit a small one.

Dyno tests show 5HP with an open deckplate and I love the sound. For me, it's a no-brainer: The deckplate stays open unless I am crossing a stream or in serious dust. I guess you could say I am addicted to the sound at WOT.

fs8459

to be honest with you, I did the elbow mod, which is similar to the deckplate and I do notice an increase in fuel mileage. The reason behind this is because of improved airflow into the engine so the engine can run more efficient which means better fuel mileage. my rig can now go an additional 35 miles on full tank after the elbow mod. I did the ISR mod at the same time and the sound is wonderful.

RockComa

Im missing something then. Here's my theory. You cut a deckplate so your filter is filtrating from the botom. What's different about opening the lid and letting it filter from the top. How a hole in the front makes a ram air setup as you say is beyond me

rimpainter.com

I should clarify my wording as I have had to do before (my fault). A better couple of words would be "direct path" for the air getting into the airbox and up through the MAFS vs. air entering the top of the box (less filter area).

I have a 6" deckplate, taking up nearly the entire front of the airbox. More filter area is exposed - way more.

However, no matter the theory, you can't get around the inferior seal created by opening the box lid to the airbox. That would be my biggest concern.

Cardesign

i think im gonna go with the elbow mod.

ewarnerusa

The lid seats the filter in place and holds it there with little clamps. when the lid is open the filter is not being held in place and you can have blow by of unfiltered air.

MTL_4runner

Christian is just using the wrong terminology but has the right idea. The path of the airflow is crucial in determining the gain (or loss) seen in the flow rate of the air as it moves through the pipe (ie past the filter and into your engine). The less restriction there is, the more efficiently the air moves and thus you will increase the ability for the engine to create power (power is directly related to airflow in this case). When you force the air to make a sharp bend or turn such as in the case of the elbow mod or even more so with leaving the top open on the airbox, this change of direction will cause some loss in airflow to take place. It is nearly impossible to calculate (you'd need to verify empirically) but it is there. The deckplate is basically a hole in the side of the airbox which allows the most direct path for the air to follow and while it is really not a true "ram air" setup (I have seen a few attempts at this) it does provide the least amount of obstruction to the incoming air's path. This is a simple example of fluid dynamics which can even be seen in something as simple as installing a dryer vent. Typically when the vent pipe has to make a 90-degree turn to pass through the floor, wall or ceiling, that 90-degree elbow is equal in restriction to a five-foot section of vent pipe. The same principle is at work in both instances.

Cardesign

MTL...are you saying the elbow mod is no good?

MTL_4runner

Not at all....just that by the laws of fluid mechanics, the deckplate is marginally better.
....exactly how much is anyone's guess.

X-AWDriver

I like the deckplate cause I can show it off to my friends,the elbow removal just isn't that impressive.

Grimace

I agree with Rick. My MAF had so much crap on it from the KN air filter, it made my gas mileage worse. I got tired of cleaning it and I now stick with the stock filter. If you you do use a Amsoil/KN filter, make sure you blow out as much oil as possible before you install it. It will save you time in the future.

DOT3

The mod decreases the resistance in your air intake. However, the HP required to move the combustion air through your intake plenum is insignificant (<< 0.1 HP) and any improvement in the flow path would lead to insignificant gains in HP. You will not get a noticeable increase in gas mileage. However, as others have said, you may gain HP at higher throttle settings due to the potential for increased air flow.

arjan

I also went back to the stock filter, didn't notice any difference and the maf stays cleaner. I just have more faith in the paper filters.
The deckplate sound good though.

Uneasy Rider

I have a K&N FIPK on my 01 Dub Cab Tacoma 3.4. While there wasn't a major difference in HP, some maybe...throttle response imroved & I picked up a few mpg. Worth it in my book. The only drawback is that it is alot louder than the stock box....not alot louder than the decplate mod though.

Tacotex

There are good dyno results on the air box mods, as well as links to filtration tests covering most of air filter brands discussed on this site. I didn't save the links, but my experience concurs with the accepted comparisons. We own 2 3.4Ls, and I have noticed similar hi rpm hp gains, but the deckplate sounds louder and is easily sealed for deep water. hp gains @ the wheels were similar. I sold both of our aftermarket filters and returned to OEM after I started watching for blowby. The stock airbox on your Toyota has a nice, soft rubber gasket that's designed to seal against a smooth, plastic frame (as in OEM). My obervations are that the greatest benefit overall is either airbox mod, and stick with the OEM air filter.