I asked this on Ck5.com but thought id thought it out here to see what ya'll think

I currently have an open element air filter on my Blazer with a K&N prefilter thingy around it. Ive been thinking of going with a dual ram air utilizing the stock pieces up in the grill and running hose to a dual ram air filter system. The kit I can get will cost $250bux, this includes the complete dual ram air filter assembly, hoses and clamps. I dont want to junk yard or piece this together, I can do the one stop shopping for these parts. But does the dual ram air have major benes over the open element. 1) Will HP increase or decrease with Ram air over open element. There is less surface area for air, but the air coming in should be cooler 2) Ram air vs open element for off roading applications such as some water (not enuff to need snorkel), dust, rain, mud etc. Im running clutch fan if that matters for slinging dirt and mud inside the engine bay. 3) Will the air indeed be cool coming thru an ram air design? Wont the air filter housing be heated up by the engine bay and thus heating the air coming in?

A proper ram air setup will always outperform a plain jane open air filter. The temp difference  can be a lot more than you think. As for the heat of the actual filter housing, the air is moving at such a rapid rate, that it doesn't have time to warm up that much. You're going to be moving a couple hundred cubic feet per minute through that housing.

I did a ton of research on this (for my 2001 Dodge Ram Quad Cab Long Bed 2500 4x4, 5.9L 360 V8), he we go:

I have checked around, and have been doing some research lately, on air filters and air intake systems. For simplicity, and over best results, I initially wanted to use an open element style kit, using a 10" or 14" round air filter.

In order to get enough CFM flow (for my wants), I would have to use a 14"x3" size filter element. There is no way I could fit a 3" tall filter on my truck. A 10"x2" K&N is only capable of doing about 690 CFM. The 10" filter also looks pretty small when mounting on a 360 V8 motor.

I tried fitting a K&K GenI FIPK, which I believe uses a 14"x2.5" filter. The fit was too tight for my liking, and I was concerned about the s-bolt (I am using a 1993 Dakota stock air filter housing bolt, which I modified and inverted), and general maintenance concerns with being able to easily access the filter, the TB, and the dist. cap/rotor.

So my research project began..........
Stock 5.9L 360/5.2L 318 Throttle Body: 635 CFM
Fastman 52MM TB: 825 CFM

I ditched the stock paper panel filter and I am currently using a drop-in K&N, until I can get all the proper parts for my own intake.

K&N Drop-In stock replacement panel filter: -#33-2084
-13.5” x 6.625” x 1”
-536 CFM

Even though I am sure the drop-in K&N flows better than the paper filter, as you can see, it still only is capable of handling 536 CFM. For $20 (what I bought mine for), it is a decent upgrade.

I then researched the K&N FIPK cold air intake kit for my truck. I really like the fact that K&N uses a large diameter flanged air filter, 4". However, if I would spend $300 on the FIPK, I was hoping it would flow more than a mere 659 CFM.

My goal was to make an intake that will be matched to the Fastman 52MM TB, and never starve for air flow.

K&N FIPK
-Kit #57-1511-2
-Filter #RC-4680 659 CFM
-Filter specs:(4” flange)6”base x 4”top x 7”long

AirAid CAI Kit
-13”x3.5” Tube
-Filter #700-420; 3.5” Flange
-6”base x 4-5/8”top x 9”long

I will have to say the K&N is very customer service friendly. Leon Collins has been great with providing myself with technical info and CFM ratings for all their filters. AirAid stated it is a rule that the CFM ratings are NOT to be released concerning all of the filters they use and sell. How pathetic! Anyways, I would imagine the #700-420 filter, that comes with the AirAid intake for my truck, ‘should’ be capable of flowing around 800 CFM.

Misc Filter:
K&N RE-0810 (3“ flange): 833 CFM
-Size: 6” base x 4.625” top x 9” long
-$46.95

Since I used a 360 Air Intakez Big Mouth Air Hat, I am only concerned with air filters that utilize a 3.5" mounting flange. I have found a few other nice air hats, but they are $200.

K&N Round Tapered Filter Cones (3.5“ flange):
#RC-5112(rubber lid); 8”base x 6.625”top x 8”long
-CFM: 1102
-$50.99
#RE-0920(rubber lid); 6”base x 4.625”top x 9”long
-CFM: 800
-$43.95
#RE-0950(rubber lid); 6”base x 4.625”top x 6”long
-CFM: 600
-$39.95
#RC-3690(metal lid); 6”base x 4.5”top x 9”long
-CFM: 890
-$46.24
#RF-1004(metal lid); 5.5”base x 4.5”top x 8”long
-CFM: 1222
-$55.95
#RF-1045(metal lid); 5.5”base x 4”top x 8”long
-CFM: 715
-$43.95

K&N Round Straight Filter Cones (3.5“ flange):
#RX-4140(X-Stream lid); 4”base/top x 5.75”long
-CFM: 357
-$51.95
#RU-5114(rubber lid); 5”base/top x 5.625”long
-CFM: 612
-$38.69
#RU-1785(rubber lid); 5” base/top x 8.5”long
-CFM: 800
-$37.95

****prices are taken from Summit Racing’s website

If ended up not buying and not using a K&n filter, since it appears as if the straight cone style filters do not have enough surface filering area, and thus cannot flow enough CFM. I did look at the RC-5112 (a little too big in size) or the RF-1004 are the top filters of choice from the K&N filters.

360 Air Intakez and Intense Performance both use S&B Power Stack band air filters.

S&B filters are really nice because, unlike K&N filters, the top of the filters are not capped off by either a solid rubber or metal plate. The S&B filters have a design in which the top is also a filter, which increases the flow rating and surface filtering area. Plus, the air can flow through the top of the air filter, rather than only being able to flow around the circumference of the filter's body (aka K&N style).

Lastly, I have found a local tube/pipe supplier that stocks both aluminum and stainless steel pipe in the 3.5" diameter that I used. This way, the air filter would use a 3.5" mounting flange, the pipe would have a 3.5" diameter, and the Big Mouth air hat also uses a 3.5" 'mouth'. This way, there are not any restrictions or reductions, nothing but smooth flowing air.

There is no way a 536 CFM drop-in filter will perform the same as 1000 CFM filter, I am going to use.

The problem with all of those expensive $200-$300 intake kits is the fact that the entire kit can only flow the the filter is capable of, and mostly likely is it still only 650-700 CFM. The air hat they use are very restrictive also.

The 14" round filters are a great simple air intake setup, if you can get a tall enough filter onto your truck. A 3" tall filter flows around 800 CFM. However, like I said, without a body lift there is not way a stock truck can safely fit that tall of filter. Add an xtreme lid and 60% of the filter lid is blocked and ineffective by the cowl and other engine parts. Once again, if you have a body lift, without a doubt get a 14"x3"-4" tall fitler and forget about it.

Take a look at the stock intake though, the air has to travel a long way before going into the TB. It has to pass up the inner passenger side fender, and who knows what kind of restrictions are in there. It then has to run through the intake tube from the passenger side fender and into the rectangular air filter housing. The long intake tube is like a 2' section of 50 speed bumps. Finally, the air can enter the air filter housing before it can be fitlered and inhaled through the TB.

I think about, the round open element filter works better for you because, air is 'there, on-demand, and 'endless'. You have 360 degrees of air going into the TB. The TB bores open up, and the air flow is instantly sucked through the filter and down into the TB. There is no waiting time for the air to have to travel through all that stock air intake nonsense.

Actually, the larger the filter.....the better the flow in the top end. If you listen to the pitch the filter makes.....you can kind of tell how its  flowing........okay......maybe I spend toooo much time dealing with intakes and filters.

The smaller filters will give you decent throttle response......but they will peak out way to early.  The pitch will change at below cruising speeds.  

The filter I used is a 6" base x 9" long filter. It gives great throttle response and off the line performance.......and yet will still flow great til about 90mph.....then the pitch changes. It still flows above that.....but not as great......but hell, I never drive that fast.

A smaller filter will probably peak out around 45 or 50mph.

One other item to keep in the equation is the intake tube size. A smaller tube will give you better offline performance but will cut out (peak) at the top end. If you haven't noticed this, the K&N/Mopar Gen-II Intake System uses a 4" tube and a 6" base x 4" top x 7" long cone filter. This system has the potenital to flow almost 900CFM, but the small filter (rc-4680)is only capable of 659 CFM.

Our trucks (94-01 Rams) use a TB that will flow up to (approx.) 600CFM on the V8's. (Modified...they'll flow even more.) However, 900CFM is a lot for a stock
(or even slightly modified) engine and we'll never see that high anyway unless we're pushing 5500+ RPM's.

I used the 360 Air Intakez Big Mouth Air Hat. No internal restrictions and it is built very well. It was about $60, shipped.

Since the intake mouth of the air hat is 3.5", I used a T6061 aluminum 3.5" OD tube.

I ended up using the S&B Power Stack 3.5" flange filters, in the 7" length. It has the top filter intake plate, that would be similar to a 9" long K&N with the flat top.

The 7" Power Stack is about $45.00 and the 3.5" aluminum tube is about $20.

I believe I stated in the above post why I am going with a 1000 CFM filter. I do not need to flow 1000 CFM and I understand and realize that my truck's motor will not use 1000 CFM.

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My rational is that I wanted to make sure I have a large enough filter that will not 'top-out' or 'peak-out'. I am running a 52MM TB that is CAPABLE of flowing 825+ CFM and I want to make sure I have an air filter that is CAPABLE is flowing atleast what the TB is CAPABLE of flowing. This way, filtered air will always be available, 'on demand'.

My on-demand theory goes back to the 14"x3" (or whatever size round filter you are using) round open element filter setups. These filters work so well because they have filtered air available, on-demand. There is unlimited air available from 360 degrees around the filter and around the TB. Air does not have to travel 3'-5'+ through a restrictive intake setup before finally hitting the TB bores (and before hitting an air filter that is only CAPABLE of handling 536 CFM).

Like I also said above, I ran a 6"x9" cone filter on my V6 Magnum truck. My Dakota ran completely different after the 1000 CFM air filter was installed. The truck pulled hard all day, throughout the RPMs.
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I now havea 2004 Dodge Dakota Quad Cab with the 4.7L motor. I bought the K&N FIPK II air intake kit. This is a very well engineered and very well built kit. However, the filter that came with the kit only flowed 675 cfm. I replaced this filter with a slightly larger S&B Power Stack filter, that flows 935 cfm.

true ram air is absoulutely useless in low speed applications.  "ram air" is a natural boost where the incommming air produces 1-3 psi of boost.  you cant get that unless youre going around 200+.  a CAI or cold air intake on the other hand will gain power

Well im running a 4" tall 12" round open element right now.

I like how my vortech rams air into my mustang

I'm setting up a carb with a functional cold air intake: Taller stud, 2 stacked 3" air filters, hole in the hood, bond-on scoop. I'm an old-skool kinda guy.

height=8

Quoted: I like how my vortech rams air into my mustang

I took a K&N to my cousins shop(engine machine) and put it on a flow bench.

I can't remember all the data, but on my stock 4.6 V8 F150 It was worth about 3hp over paper element.

Taking the volume of each cylinder and I think it was 1.5 cfm per horsepower, the flow rate difference was minor. You would be hard pressed to "outflow" your stock paper element unless you vehicle was significantly modified to a point you needed a new fuel system.


A reduction of 4mm vacuum in the intake system was good for about 10hp. This would be like adding 2 psi to the airbox, so if you hook up a pressure gauge to the airbox you would need to see 2psi for a 10hp gain, guess what............. it isn't going to happen very easily. You may see 1 psi at 80-90 mph.

An open element underhood is also a power robber, a drop of 1% for every 10 degrees. Underhood temps can easily be 130F in 80 degree weather netting you a 5% loss, as hotter air is less dense, and equates to less o2 available. Not to mention most fuel injected motors have intake air sensors, that monitor intake charge temps. A hotter air charge will result in the EEC pulling out timing advance, which means even less power. I think my 93 Mustang (Supercharged)at 100 degrees pulled out 6 degrees of timing, easily 20-25 hp .

K&N filters suck, well not just K&N any that tout themselves as high flow. Bottom line is they let more dirt in your motor. While they say it stops 98% www.knfilters.com/filter_facts.htmof dirt according to the SAE J726 or ISO 5011, there are 3 sections of the test. A course(J726C), medium(J726M) and fine(J726F) particulate matter, they only test it to the course section of the test, very misleading.(from their website)" The ability of an air filter to protect your engine is generally measured in accordance with testing procedure ISO 5011.  We subject a sample of our filter designs to this test procedure using Coarse Test Dust, which includes particles ranging in size from less than 5.5 microns to 176 microns" so the medium and fine shit go right into your motor.

Ask anyone who gets oil analysis done, put on a K&N and watch the silicon (dirt)content go up.

Have a look, I didn't make this shit up

www.duramax-diesel.com/spicer/index.htm

Oh, yea I have one(K&N) on the Mustang, it needs high flow with the Supercharger, and if I was worried about longevity I wouldn't have put a blower on it . Yes I change the oil often