It could be more of a filter restriction than a box restriction.

When my filter was new I could pull the filter minder down about a third of the way at WOT. I took the filter out, removed the gauze fiber thing over the paper filter and have not seen the filter minder move since. I know it is there for prefilter or so the filter can hold more dirt but if I remove the filter and clean it by lightly tapping once and awhile I can accomplish the same thing and get a better flowing air filter.

 

in/h20 is a mesurment of vaccume, just like in/hg, just on a smaller scale. ie in/lb vs. ft/lb.

a flilter that flows 100 cfm @ 1 in/h20 will out flow a filter that flows 100 cfm @ 10 in/h20.

its the same way carbs are rated. ie holley rats 4v carbs at 1.5 in/h2o but rates the 2v's @3in/h20. if you look at the throtle area on a 600 cfm 4v and compare it to the throttle area of the 650 cfm 2v, the 4v has quite a bit larfer throttle openeing than the 2v.

 

So how many cfm does our turbo flow? You only need to be able to move that much air through the intake. Having an intake set up that flows a bazillion cfm does no good if it's not usable air.

 

Almost any setup will flow what the engine needs, the questions should really be, how EASILY it allows that CFM and for how long will the filter support that CFM in it's life.

My question I'd like answered is what the stock ratings are. AK Ram says:

But that doesn't seem realistic to me comparing it to filters of similar surface area. I beleive it's 452 CFM at 6" H2O which makes more sense.

 

To you guys that have drilled out your air boxes, Do you notice more turbo whistle?? The only mod Im looking to do on my rig is, drill the stock airbox for a little more air, and replace my intake tube with that pipe from Air Flow Systems. Im looking for a little more whistle, little better air flow, for little dollars!! Not looking for a huge difference, what ever gains I get, is more than I had.

 

I didn't drill out the bottom like most guys. I cut out the whole front side. I cannot here any difference than before in turbo whistle or any air noise at all.

 

Drilled my holes last night and I can not beleive the difference. There is no additional noise that I can tell, but what I can see is the performance. From a dead stop I could chirp the tires, now with the holes in the air box the turbo spools up much quicker and when it does the tires break loose, both times I backed off, I do not have extra $ to throw on tires but I had black marks for 30+ feet. Another thing that I noticed is that I have not seen any black smoke? Maybe is was starving for air. I have not checked my filter minder yet to see if it has moved.

Thanks for the idea.

 

I'm going to do this mod tomarrow along with the tone ring. A buddy is comming over & helping (hold my beer) to see the results & maybe do his 05.
I've been telling myself I'm going to leave this truck stock to keep my warrenty since I got it in august.
Has anyone done an oil sample to see if the silicon levels are ok with holes drilled & stock filter?

 

I just drilled out about ten holes in the bottom of air box replaced filter with a wiks.Driving up to phx tomorrow . long and flat drive hopefully this will help a little more.

 

Badd Dogg,
When I installed a 4" drain pipe elbow on the bottom of the airbox it didn't do much for the turbo noise. What made the big difference was removing the silencer ring on the turbo and replacing the air tube silencer with a piece of 5.5" aluminum tubing. Now she sings!

MikeyB

 

I took out my silencer ring and replaced my intake tube with a piece of 5.5" aluminum intake tubing also, i thought my turbo sounds was awesome... well my buddy just got done putting an MBRP 4" exhaust and an AFE PG7 intake on his 04 6.0 PSD , HOLY COW!!!!!!!!! that turbo is almost annoyingly loud!!!

on a side not, he also just put on a juice/attitude and that replaced his superchips, im actually not impressed with the juice compared to the superchips...

 

Regarding filter restriction numbers - when it says 100cfm @ 6" h2o, that means it takes a 6" of h2o pressure difference across the filter to flow 100cfm. If another filter flows 100cfm with 4" restriction, it flows "better" in that it takes less pressure across the filter for the same flow. Keep in mind that for air to flow through a filter you must have "vaccuum" (less than atmorspheric pressure) on the intake side, the question is just how much to get the required flow.

Also - inches of water is just a unit for measuring small pressures drops, and is commonly used for air filter restriction because they are small numbers. 1" of water = 0.036 psi.

Mathew

 

or 1"hg = 13.596"h2o

 

The more I learn the less I know ... I talked again with Fleetguard technical assistance but it wasn't much help.

I was told the stock filter provides an initial restriction of 4.66" H2O right up until it plugs where it hits 16" H2O. Riiggghhht. So what happens when the engine (a bombed 5.9) demands more than the 452 CFM it was designed for? Dont know but my guess is either the filter implodes (haven't heard too much of this happening) or the restriction must skyrocket. Anyway, it's designed to deliver 452 CFM and thats it, clean or dirty.

This I guess is where the benefit of standard BHAF comes in. It's designed to deliver 687 CFM all day long. Sure it's at a higher restriction, but maybe that's not the big deal some of us think it is. The turbo is going to suck the intake track to a vacuum if it needs to to get the air it wants. The extra work needed to get it maybe doesn't effect the performance enough to matter.

I still don't see the benefit of opening up the stock air box. What CFM does that fender opening support at a reasonable restriction? I would think it's far more than any modified 5.9 would need.

 

I don't know. I'm waiting for someone else to do all of the research and then just tell me what to do.

In the meantime, the combination of my modified air box and homemade torque tube seem to be getting the job done.