Lazarus-F150

Hi Everyone,
I've been thinking about making the switch to a K&N open air set-up for a while and finally had the time to do it recently and thought that I would post some pics and a parts list in case anyone else was thinking about it. Here goes:

K&N universal filter (#RF1012)
3" OD to 3" ID exhaust pipe adapter x 2 (AutoZone, not shown below)
3/4" to 1/2" brass barbed reducer (Lowes)
9/16" to 17/16" stainless steel hose clamps x 2 (Lowes)
3/4" x 1/8" aluminum flat bar (Lowes)
1/4"x20 stainless steel nuts (Lowes)
1/4" stainless steel lock washers (Lowes)
#8 x 3/4" TEKS screws (Lowes)
Angle grinder with cutting and grinding disks
Metal file
Drill and drill bits


Start by separating the intake tubes from air filter box. The filter box lid can then be removed (four screws at the four corners) followed by the bottom by removing two screws in the middle of the box. After removal of the box, you will see the metal mounting bracket.



The metal mounting bracket also supports the washer fluid and coolant overflow reservoirs, so it cannot be removed. Instead, I decided to cut the portion that served as the mounting point for the old filter box using an angle grinder with a cutting disk. I cut the small pillar mount (yellow circle) first to make some more space to work, then cut the two joints with the remaining part of the reservoir bracket (red circles). Be careful here as there is a wire bundle immediately below the cutting point closest to the body (red arrow). After the cuts have been made, remove the mounting screw (blue circle) and this part of the bracket can be removed. The cut edges were pretty sharp, so I took a grinder to them to prevent future injuries...



I took a second to wipe the fender well off (me being neurotic, not required)



Next, assemble the new filter and adapters. Insert the 3/4"x1/2" brass reducer in the PCV port and secure it with a hose clamp. Insert the narrow end (3" OD) of each 3" OD to 3" ID adapters into the filter's intake ports (I filed the burs from each end of the adapters first) and tighten the hose clamps that come on the filter ports. Install one 1/4" nut on the threaded post on the polished top of the filter (I also used some Loctite here). Install the filter (PCV port facing up) by sliding the intake tubes over the exposed metal adapters (3" ID side) and tighten the hose clamps. Then measure and cut the exiting PCV hose to length to be installed on the brass barb (don't forget to slide a hose clamp on the PCV line first). Slide the PCV hose onto the brass barb and tighten the hose clamp. Now, cut a length of the aluminum flat bar to make the mounting bracket. Drill a 1/4" hole at one end, which will fit on the threaded post on the filter. Drill two additional holes on the other end of the bracket and make a slight S-bend in the middle of the bracket. I filed the cut ends of the aluminum bracket to remove the sharp edges. Run the filter's threaded post through the 1/4" single hole then add a lock washer and nut (I also added some Loctite on the post here). Note the position that the two holes on the other end of the bracket will contact the side of the engine compartment, drill small pilot holes, and install with TEKS screws and lock washers. Overall, not too long of a job and it was pretty straightforward with the right tools. I would definitely recommend it!

Eric Fullerton

That likely will actually cost hp and torque due to breathing hotter air than the airbox would supply. The stock setup is overkill on the 4.9 to begin with.

Steve83

Right - expect a slight loss in hp & torque due to the hot-air intake. But don't be surprised if you convince yourself that they INcreased. Butt-dynos aren't known for accuracy.

If you want an actual slight increase, insulate the plastic tubes & filter box to keep the air charge cooler.

BareBonesXL

Without getting in to all of the opinions, could you just explain why? Why have you been thinking about it and why did you make the final decision?

I think that that's what drives most of the K&N arguments. It's like somebody got on the forum and said "I've been thinking about chopping off my little finger, and finally decided to do it".

Don't take offense at that last remark I just put it there to try to define the confusion. There might be a reason. What is it?

And, at the end, why do you recommend it?

Lazarus-F150

Great question BareBones. First, I agree completely that the K&N set-up will lead to an increase in the intake air temperature; however, that is only part of the equation. Also, I will apologize in advance for the lengthy response, but I'm an inhalation toxicologist in the time that I don't spend keeping my truck up and running (and dealing with two crazy dogs) and the factors that affect air flow going into the engine aren't all that different from those affecting air flow going into the lungs. Here's what I'm thinking...

If we assume that the primary factor involved in choosing an intake set-up is the amount of air that makes it into the cylinders, then we have to consider total air flow, which depends on both the density and volume of air that are allowed into the cylinders. The primary argument against an open air set-up is that the intake air temperature increases, which means that the density of incoming air would be lower. While this is true, the effect of temperature on air density is relatively modest (I've copied a table below). For example, if the intake air temperature increases by 50 degrees (Fahrenheit), then the density of the air will decrease about 10% (assuming that the open air set-up doesn't have an effect on how high the truck sits above sea level). If we use 50 degrees as a benchmark, which is likely a pretty substantial over-estimation of the actual increase in intake air temperature, then the K&N set-up only needs to increase the volume of air entering the engine by 10% to "break even." Now it's down to a question of whether the K&N set-up allows for an increase in intake air volume. In my mind, this question has two distinct components of a physics problem. First, the mesh of the K&N filter is mush less restrictive than the original paper filter. Second, the snorkel that feeds the factory air box has some pretty tight bends that notably reduce the ability of air to flow into the air box, even when the air is being "forced" into the snorkel by the forward motion of the truck rolling down the road. At the end of the day, I decided on this set-up because it seemed reasonable to think that the increased airflow that was allowed by the K&N filter and loss of the factory snorkel set-up would be more than enough to overcome the lower air density that resulted from the increase in temperature that comes with the open air set-up.

Eric Fullerton

Problem is; the stock setup is pretty much what is supplied with a V8 & IIRC even the 460. It already flows more that the 4.9 can pass at wide open throttle. The exhaust and the head could use some improvement, but the air intake is already flowing more than the engine can pass.

Lazarus-F150

I don't know the actual flow specs for either set-up, but if the 4.9 was running at 1500 RPM then it would need 7350 liters of air per minute (4.9 liters of volume displaced per revolution), which breaks down to 122.5 liters per second, to achieve full capacity. I'll fully admit that it's a guess, but I would think that either set-up would have a hard time allowing that kind of volume to flow in. Am I missing something here, or have flow rate tests been posted? I'm definitely interested.

BareBonesXL

You didn't really define what you were trying to achieve or improve. I'm going to guess that you're looking for more air flow, because that could lead to an increase in power, assuming that air flow was restricted by the filter, before. So, in short, you thought it might give a bump in power, and the dustier air that will reduce the life of the motor is a worthy trade-off. But, at the end you said that you might just break even, with the warmer air offsetting the increased flow. So, in sum, dirtier air, and the same amount of power.

If lower filter restriction is really the goal, then the solution is just more surface area. A bigger paper filter would provide more clean air. So, a bigger air box, with the corners smoothed, and the pipes to the throttle body enlarged. That would fit the goal and keep the air clean.

Good luck. I understand the urge to improve things if you can. The math just doesn't add up on the K&N CAI's though. It's a heavily marketed con..

Lazarus-F150

Interesting points. Answers below:

It would be nice to get more power, but I agree that any gains in hp/torque, if any, would be marginal at best. My main interest is in increasing throttle response since I do more stop-and-go driving than drag racing. You may be right that increasing the effective pore size of the filter by going to the K&N will lead to dirtier air going into the engine; however, once particulates are filtered out down to a certain size, their impact on engine wear will be negligible. As far as I know (please correct me if I am wrong), the primary concern there is particulates in the intake air is them getting into the oil and causing an increased rate of abrasion/wear. When considered in isolation, that concern makes sense to a certain point, but most airborne particulates readily breakdown when subjected to shear/compression forces, such as those that they would experience between a piston ring and the cylinder wall. Further, the mass of most airborne particulates is substantially organic, which will result in minimally partial dissolution in the engine oil, which is also organic (in the chemical sense, not the tree-hugging sense). Engine lubrication systems are designed to accommodate the presence of particulates in the oil since they come in through the intake (regardless of filter material) and enter the oil as a result of the normal combustion in the cylinders, which is why old/used oil is nearly black. The dark coloration comes from the accumulation of particulates during combustion over the time that the oil is in the motor. The engine lubrication system also has its own filtration system that removes ~98-99% of particulates larger than 1 micron from the oil (keep in mind that the vast majority of airborne particulates - by mass - in ambient air are larger than 10 microns, which will also get filtered out by the K&N filter and never enter the engine anyway). With proper oil system maintenance, I wouldn't be concerned that any ultrafine particles that get through the K&N filter would have any real effect on engine wear.

Similar to above, I don't have actual numbers to show, but I would bet that the amount of particulates generated by the firing of each cylinder every revolution would exceed what can get through a K&N filter. Intake filters primarily serve to prevent larger particles/insects/etc from entering the engine, which the K&N filter will do.

Agreed, but it would be a huge effort to do all of that, and as you pointed out earlier, it's not likely to result in an appreciable gains.

I agree that K&N over-promises with respect to their products, especially cold air intakes; however, they didn't make any promises for this application, so I'll let them off the hook for this one

Eric Fullerton

If you really want to increase throttle response or at leas overall performance, the big restriction is the U flow, small port head. Not much you can do about that, at least not easily or cheaply, there are some improved heads in the works, but they will likely cost more than most of us have in our trucks. No cross flow heads in production that I know about. What you can do relatively cheaply is get a 3" exhaust from the down pipes back, Cat, muffler and all. There is also a restriction where the EFI manifolds meet the head pipe. the opening there is 1.75" and that can be opened up a little and still get a good seal, The head pipes are 2" so not much point in going more than that.