I am trying to figure out what size of air filter I need for my truck.

The K&N website says the minimum size filter area (A) can be found by this formula:

A=(cubic inch displacement(CID) X RPM)/20839

I'm pretty sure there is some type of formula to figure out the CID of a supercharged, but I don't know what that is.

Looking in the Turbonetics catalog it says a 9"long by 6" base x 4.63 top K&N filter is good for 625 HP. By my math that filter has about 150 square inches of area. The 12" long x 6" base x 4.63" top is good for 850 HP. By my math that filter has about 200 square inches of area. The 14" long x 6" base x 4.63" top is good for 1000 HP. By my calculations that is about 234 square inches of area.

The formula I used was surface area= (Pi(base radius+top radius)filter length) I think that formula works, but I'm not a math expert.

I'm guessing my max HP is around 600-625 fwhp since my highest dyno was 567 rwhp.

I should be okay with the K&N 9" filter, but why does everyone go with the 12"?

 

People think bigger is always better....

 

And some people think that old addage is always a true *catch all*.

On an oiled filter you want the biggest surface area you can get. The velocity per open cell will be lower and the filtration will be better.

WOT

 

I was thinking about modifying the cool air kit I have for my old 5.3 GMC and using the venturi adapter. I would hook that to the filter adapter, then I could use an RF1041, 150 square inch, or a RF1026 for a 250 square inch surface area.

 

Leonard.......your formula is correct here is the long form:

((2*Pi*R1+2*Pi*R2)/2)*H

So.....((2*3.14*2.315"+2*3.14*3")/2)*12" = 200.37"

--Joe

 

Sal's comments from a while ago: http://198.65.157.241/forums/showthr...erstack+filter

And, here are some different sizes: http://intenseperformance.com/produc...e_filters.html

Dan

 

I'm more interested in the surfacre area that is needed for a specific horsepower, not in what was needed back in mid 2001 or earlier when the biggest supercharger overdrive pulley you could get was a 6lber.

 

Why not go with the biggest filter you can fit? How much HP will the 12" open ended cone filter cover? I can't imagine a bigger filter causing HP loss, since no filter usually allows the most hp. Therefore, a huge filter should filter more and allow the most airflow.

 

I have an RF1041 and wanted to know if it would work and allow enough air for my application. I figured someone would know if 150 square inches would be enough area for 600-650 HP. I also don't want to buy filters from tuners if I can buy them wholesale myself.

 

easter
here's another clue, the K&N catalog says that there filters flow roughly 6 cfm per pleated square inch, and that is at a restriction of only 1.5" H20 ( I think).

I have learned that the MAF is sensitive to the way the air enters it.
In stock condition the MAF is attached to a big air box, with the air flowing from a specific direction.

These are just minor observations.

I will tell you this....back in the old days when the Pro-M 80mm sensor was the rage. I tried one of those sensors and also tried several different filter combos with it. I got rid of the little K&N that came with it and stepped up to a much larger filter, this worked really good but then the S&B Powerstack filters came along. I found an S&B filter that would fit the Pro-M that was about the same size as the K&N I was using, my thinking was that since the filter flowed from the end also, that it would run a little better. I was wrong. Apparently the Pro-M didn't like the way the air was flowing from the filter, cause the truck fell on its face. Another way to say it is that the Pro-M didn't like the way the S&B was conditioning the air. (maybe too much turbulence) I did several back to back tests so I am pretty sure of what was happening.

Sal even told me one time that the sensor seems to have problems with filters with a rubber cap on the end of them (like most K&N's) because they can flutter and cause metering problems.

I guess what I am getting at is that I would run the biggest filter you can get under the hood. This will slow the air speed down thru the filter, but it still has to be pointed in the right direction.

My latest filter setup is a 14" K&N cone filter with a solid plate glued to the end of it. In this case......Bigger doesn't hurt anything.
Dale

 

so... which k&n do most people get.. i want to replace the stock air box, but I'm all stock now, likely wont be adding a chip or pulley any time soon for fear of breaking my $20k liability

 

the filter in the truck works fine for stock. If you want to get a flat K&N go for it. An open filter will do nothing for a stock truck.

 

I have a 2000 Lightning and I am about to order a JDM cold air intake and Silver Bullet Cat-Back Exhaust. I am not chipping my truck yet so are you saying the cold air intake will do nothing for me since I am staying at the 80mm MAF?

Thanks

P.S. Can I expect any horsepower increase with the above modifications?

 

The cold air intake will give you a few ponies on an otherwise completly stock intake / truck.

On my first trip to the track when it was bone stock; I put in a K&N panel w/two holes in the bott of the stock air box as well as removed the rubber snorkle.

Just that alone gave me about 1 more psi and dropped the 1/4 ET by a repeateable 0.1 and the mph went up by 1-1.5.

Where an aftermarket unit will come into play much better is at elevated boost levels.

WOT

 

Catback=no performance gain.
air filter with out at least 3-4psi added boost = hotter intake air temps and no gains.

That is what I have seen. A lot of people like the look of the aftermarket filter and the fact that the blower whine is louder with the aftermarket filter. The cat back will make the truck sound better than stock.