2001 5.4L

the throttle body diameter appears to be about 68 mm

the infamous "snorkle" restrictor in the fender well is about 52 mm

a 68 mm hole is 71% bigger than a 52 mm hole!

of course by no means will the system flow 71% more, but we are all thinking it's gotta help, right?

there may be other areas between the TB and fender well that are smaller than 68mm...

But...i'm having trouble understanding, if it does help, why Ford wouldn't have made it bigger in the first place?

i'm not buying the "noise" explanation. Actually, a larger hole with a lower velocity is quieter.

With the "horsepower wars/bragging rights" factor, if they could claim even another 5 horsepower by molding that stupid snorkle a little bigger, wouldn't they do it? If not, why not?

Has anyone done a dyno run before/after with nothing else changed other than the snorkle?

 

Don't have any dyno numbers but I did notice a big seat-of-the-pants difference when I did the modification that removes the portion of the factory housing that encloses the filter. It leaves the filter out in the open under the hood. With the filter attached to the stock intake this way the truck seemed to be doggy off the line and it got worse as the engine got warmer and the outside temperature got warmer. It was much louder also just like in the old days when you would turn the top of the air cleaner upside down.

 

if u just take the snorkle off u will see a difference but nothin like seat of ur pants

 

dont do the poor man's cold air intake mod (one that exposes the K&N filter wide open) it draws to much hot air, I noticed no difference in performance but I lost a solid 1.5-2mpg & I know that for a fact..

 

Alot of what Ford and the others do is because of government regulations. Air restrictions into and out of the engine to meet requirements yada yada.

 

It is done to reduce the interior roar at wide throttle openings.
Doing the same kinds of things to exhaust also reduces noise output.
If it bothers you to much, here is a way to alter it.
At hardware store get a short piece of alum dryer hose the same size as the housing inlet.
Slide it on the housing, cut to about 5" without expanding it's length.
Wrap duct tape around the alum only. Paint black to match the stock color.
Form the inlet end to a rectangle to match the opening in the panel and slide it in then finish forming to the shape of the panel opening and your done,
No more percieved restriction.
I claim no wild hp or mileage increases!!!

 

ok heres what i got.

for every 10*F rise of air temp you lose 1HP. Open filter boxes decrease HP and gas milage, but sounds cool.

If you want to get a little more HP. buy some thermal exhaust wrap (looks like braided cotton but is fiberglass based,) do your intake pipes that are in the engine compartment, and your exhaust manifolds.

heres the "method of my madness"

the colder the air, the denser it gets. dense air = more air can fit in the cylinder = more cylinder compression = more combustability = more horsepower. Nitrous oxide has the same effect just on a HUGE scale. for those of you that think nitrous is flammable your nuts. Nitrous oxide is COLD when released from a pressurized system. All it does is make the air in the cylinder super dense jacking the compression through the roof creating a lean condition, and THATS why it can fry your rings worse than Richard Prior. moral of that story, get one that add gas as well as nitrous. also refered to as a "WET SYSTEM"

the ambient temp under a closed hood is near the 150-170*F range on a spring day ~70*f

the temp out under the fender is ~70*F still right? so if you are sucking 70* air, but passing it through a 150* tube, it raises the temp of intake air.

sorry for the rant.

AS for the size of the tube. bigger is better, but dont cheat and pull the airbox apart. it shows no gain, and will actually hurt performance.

SIDE NOTE: the tornado air thing is dumb. i dont care if the air going into my tb does the irish jig, air is air. spinning air is still air.

p.s. NOS is a brand name.

---NAH2323
Airhead.

 

don't forget that with NOS we are bringing extra oxygen to the party...actually, the cooling effect is good but secondary.

after drigving the truck with the "dryer vent" mod, can I tell a difference? Well, it's hard to say...sure doesn't feel like it lost anything...

Yes, I was also thinking of some type of insulation or double-walled setup to keep the charge cooler.

 

correct nitrous oxide does bring oxygen to the party only to give it combustability. otherwise it would be like filling your cylinder with CO2. NFG.

you will be surprised what the thermal wrap does. some companies have designed airboxes that hold ice to create super cold intake air temps for short periods of time.

dryer vent mod may gain you a lil power, but not enough to feel. its a WOT mod that would be most beneficial during towing, or drag racing.

 

I always go back to the test done by Neal the HP freak, while moving, the temp around an open filter in his truck was within 5* of outside air temp. Yes it is a little doggy off the line after sitting for a few minutes idling, but it doesn't take long to overcome the difference with underhood airflow. Stock snorkel is about 2 inches, the airbox inlet is roughly three inches. Bigger means more volume of air moved = more power. It's not a huge difference, but I could feel and hear the difference. Three inch exhaust pipe will slip over the airbox end without too much work.,,,,98

 

Anyone have a pic of their airbox mods? I don't like the exposed filters to much and I also don't want to chop up my truck either.

 

Mine, please excuse the dirtiness. It's been in the garage since I put the K&N intake back on.,,,,98

Looks huge, but it's just the perspective of the picture. 3 inch exhaust pipe slipped over the end of the stock airbox.

 

it could be possible that the stock intake system is designed as a resonant chamber. I would guess that the resonant frequency would be around 2000-3000 rpm. This would mean that our modification probably moves the resonant frequency way out of the ballpark, taking away low end but adding a bit of full throttle high rpm power. I've seen this theory proven out on other engines, but no dyno info for our F150s. Most folks naturally think that having the least restriction possible will give the most horsepower.


For example, on some motorcycles, removing the stock airbox/intake and running open "pod" type filters will only gain a few hp on top, but will rob power and driveability in all other ranges. I'm not saying this is the case with our trucks, since I have no access to a dyno.

 

Thanks for the pic, that's what I had envisioned.