*insane nonsense rant warning*
Ok I'm fully against "cold air intakes" but I have been a fan of using k&n filters (direct replacements, not cone filters or nonsense). I am well aware that if you don't know how to oil them properly they can mess up your maf sensor. But I don't drive in dusty conditions so I like being able to take it out and clean it whenever and throw it back in.
Been using K&N filters in everything for 20 years. Recently I'm fighting with my truck over fuel trims being high. I said lemme try something and stuck a motorcraft paper filter in it. (It's had a K&N since 2009). Fuel trims came down and evened out across the throttle range.
So... here's my thought here. Given positive fuel trims, the k&n filter obviously flowed more air than the ford filter. BUT do those numbers equate to a power increase or just reduced fuel consumption when dealing with a modern sophisticated efi system?
Dirtman:
We'll see if I can explain this...
Ford engineers need to compromise on every component - a CAI that works great in summer in Tallahassee, Florida, doesn't work worth $#!+ in winter an hour north of Fort McMurray, Alberta, an air filter that needs maintenance after 20 miles off pavement doesn't work for my in-laws who drive 13 miles each way to town on gravel roads - they aren't going to clean and re-oil the filter after every trip, etc.
K&N filter flows more air (as do headers, CAI, etc), which an efi system in closed loop, compensates for adding MORE fuel. Which is why you are seeing higher fuel trims. One can do the same with a carb by installing larger jets. More air & more fuel equals more power which is why the brochure will quote xx hp increase at peak RPM and WOT.
More power
reduces fuel economy if you keep the same throttle position. But, when we are driving constant speed e.g. 55 on interstate
, the increased power allows decrease in throttle position (less push on the skinny pedal), so you MIGHT see increased fuel economy. There's a very complex trade off between more efficient engine and "throttled" intake - the 2 basically work against each other and you don't gain as much as you thought you would based on the quoted hp increase.
Does that help?