Derestricting Intake - Removing MAF Screen

[Rey]

I removed my MAF (mass airflow) screen 5000 miles ago, and can report no issues whatsoever. It is hard to definitively determine power and mileage increases, but I can report no mileage decreases.
The MAF screen resides at the mouth of the plastic air filter cover. Unlike GM products which are glued in place (and often require destruction to remove), Hyundai merely presses it in place. It takes five minutes to gently press it out - careful not to disturb wires in the MAF. It is even easier to restore.
I did a some research before I did this mod. I even bought a spare MAF just in case I had to destroy the screen for removal. Most of the research on the subject is through GM sites; where owners frequently remove the screen. Basically, the Genesis screen in the Hyundai intake tract is identical to the 2004-07 Cadillac CTS-V. GM introduced the screens on truck intakes with the view of a need to straighten airflow so the signal to the MAF wires would be uniform and constant. They continued this on to autos. Recently, it seems that GM has removed the screens on Corvettes, and perhaps on other models.
As best I can tell the screen restricts airflow at a bit less than 8%. I did not feel a power increase, but generally it takes at least a 10% power increase to be felt by one's "seat of butt dyno".
Lack of a MAF screen potentially can result in low rpm stutter and light throttle tip-in stumble because of tumbling air flow. At WOT (wide open throttle) airflow is comparatively smooth. I have experienced neither of these problems.
As for intake noise, it is very nice in my opinion. There is no hissing or honking intake noise. There is no intake noise at cruise or light throttle increase. At moderate or more throttle increase there is a motor sound, but that is even loud. My wife, who is very sensitive to noise increases, never noticed this change.

 

[JDC]

I'd suspect that with the MAF successfully removed = more air flow = a bit lower MPG as well, if the A/F is being kept constant ratio.

What do you think?

 

[Rey]

Derestricting either exhaust or intake has a general effect of increasing gas mileage, provided fuel/air ratio remains at 14.7, which it does on my car I have a reference quality air fuel ratio meter which confirms this mixture. I did this mod on a recent trip and gas mileage "appeared" to increase. I say this with the caveat that over-the-road experience varies so much from day to day as to blur the measurement of changes. A headwind or tailwind can alone change gas mileage 10% either way.
I did try to establish a personal baseline recently. I did a 100 mile test at a steady 65 mph on flat ground. Here were my test condtiions:
Air temperature: 68F
Wind: from Northeast 10-15 mph. Exact quadrant in degrees unknown.
Test directions: about 40 miles due west and about 60 miles due north.
Speed managed entirely by cruise control. There were several 55 mph construction sections where speed was reduced. Average speed was 63 mph.
Car was fully warmed with at least 100+ miles of driving before test.
Gas mileage over test distance was 34.4 mpg. Note, this was not "real driving". My day to day real driving on highways at 5+ over speed limit with cruise speeds from 70-85 varies greatly, but usually above 27 mpg, except with a stiff headwind where I have seen mileage drop to as low as 23 mpg. My baseline was solely for comparison purposes, and because conditions were comparatively good for such a test.

 

[ctrcbob]

I owned my care for "months" without ever seeing that there was this screen in the upper removable section of the airbox. It is a light green screen and I use the word screen loosely, as it looks more like a foam filter. It passes air very easy, as I can breath through it with no problem. I decided to clean it, as it had been in the car for many miles. Snapped the "cage" that encloses it, removed the screen, then washed it in warm soapy water. No dirt at all. The engine filter does it job as nothing gets to the screen. After I washed and rinsed the screen out, I allowed it to dry in the breeze outside. Installed it back in its cage and snapped the cage into the top of the airbox.

I figure that Hyundai has a reason for this screen, so I leave it in. Because it stays clean, I probably will never remove/clean it again.

As some of you may remember, I also installed a "pre-filter" in front of the air intake, above the radiator which I pre-oiled with filter oil, and used it when I knew I was going to drive through dust storms in Arizona and New Mexico last year. This pre-filter was cut from window A/C filter material and cut to form. After I drove through those three dust storms, I checked the engine compartment and pre-filter, and everything was covered with RED DUST. Pre-filter was loaded with this dust. After I cleaned this pre-filter, and cleaned out the engine compartment, I then looked at the stock engine air filter, and it was clean. No red dust. I have since learned that when you punch the gas hard, a trap door opens on the bottom of the airbox, bypassing the regular air intake (and my pre-filter). I guess when I was driving through those dust storms, I did not hit the gas hard, as no red dust went through the trap door into the stock air filter.

I leave everything stock, (not cold air intake) because when needed, that trap door in the bottom of the airbox opens, and in effect, it becomes a cold air intake.

The guys at Hyundai know what they are doing!