The filter and air flow is such a big factor which contributes directly to the HP of the engine and so easy for an engineer to calculate that Ford is not going to screw that up. It's a simple as; would you put a newspaper in front of your home fan when you are trying to cool off? I'm sure there is a fine line between passing enough air at high RPMs and maximum filtering with a cushion for a dirty filter and I am sure they dialed the funtionality in very well.

 

Wow, there sure are alot of dummies throwing money away on 6637 filters.

Those 'covers' add a second level of filtration. The 'filter' allows more air into the intake. As you call it, warm underhood air, entering the air filter is a moot point. What do you think happens to the air when it hits that hot turbo?
That's why we have intercoolers... to cool the incoming aircharge.

The 6637 filter is for the turbo diesel. On a gas motor, yes you want to keep your intake as cold as possible because the colder the air, the more oxygen it has in it.
On turbo diesels, you can still try to cool your incoming air but the turbo warms it up enough to make the intercooler neccessary... to COOL the aircharge before entering the intake.

The 6637 filter is worth the trade off, heat vs additional air. Especially on a modded set up.

 

You are missing an important factor when OEM's design vehicle intakes and that is noise and resonance or vibration. probably 90% or more of buyers are more interested in it being smooth and quiet than getting that little bit more performance... for example you can hear the turbo whistle after doing a 6637 mod or Zoodad mod that would be unacceptable for most vehicle owners ... Enthusiasts excluded . Thus there is a trade off to get that quiet smooth air intake

 

The mechanism of filtration? No-one mentioned that yet.

A K&N filter is oiled, and so its characteristics are different. If I remember correctly, straining filtration is worse than stock paper filters, but impaction and impingement are better, as are diffusive means of filtration, because of the oil.

Think that is right, it has been a while.

Of course, if a K&N is not maintained, it ceases to provide adequate protection. The increase in air flow is facilitated by a lower pressure drop and this means lower straining filtration efficiency. Lose the impaction, impingement and diffusive advantage because the oil is gone, and you're worse off than with a paper filter.

However, and over oiled K&N can wreak havoc with the MAF sensors on modern vehicles. I only use them on carbureted stuff.

The Mann filters I use on my BMWs are now starting to add a foam prefilter over the paper pleats, really nice filter. Best disposable I've seen.

 

I am more familiar with gas motors but it doesn't make since that Ford is going put an inefficient filter in any engine. Cold air will benefit any engine because it contains for oxygen but I guess diesels can't benefit from it.

 

You will never convince me that Ford compromises their horsepower for noise and vibration reduction. The proper size and design of a filter and it's induction system will acommodate those problems.

 

Really??? Did you not read my post at all??? I said cold air contains more oxygen. You obviously know zero about turbos. Go pop the hood and touch a turbo right after it's been run hard, then, after you peel your hand off of it maybe you'll understand what I'm saying.
Southpaw is right, Ford, Chevy, they all do it. They build the cars to fit most buyers. If this wasn't so, there wouldn't be the aftermarket support there is today. Your average soccer mom who buys an Excursion doesn't want to hear turbo wine or the intake sucking sound of a gasser with an open element filter. Should I even mention exhaust?

The air is already hot AFTER the turbo. Cold air coming into the filter will HEAT up as it runs through the turbo. Hence the INTERCOOLER .

I have no words for this at all. Unbelievable, I need some asprin.

 

I know a little about turbos. So you are saying Ford builds diesel trucks to please soccer moms? I'm going to have a taquila sunrise.
Wait! I get it; Ford carefully designs their cams, combustion chambers, induction system, fuel injectors, etc, for maximum horsepower per cubic inch while still maintaining decent gas mileage and then they sabotage it all with an inefficient air filtration system. That's it!