K&N filters

[gduke2010]

I finally installed a K&N air filter in my 2007 Ford F-150 after numerous oil changes and 50,000 miles. The filter cost $42 which is less expensive than the 5 $15 paper filters that I bought since buying the truck new. It seems to be a good investment, after 1000 miles the trucks fuel economy improved from 16.3 mpg to 17.6 mpg. The day I changed my oil, I went to the local auto parts store in Minden and the kid at the counter asked, " do you want a K&N filter we have 1 in stock?"

I thought, why hadn't I bought one the first time the filter needed changed and said," sure what do they cost $42?"

"Yep, $42.

So, my friend bought one for her Jeep Commander.

Thumbs up for K&N.

Gary

[sc_rufctr]

They do work well and are a great option.

However often people install them and then don't maintain them properly. They need to be serviced at least once a year...

Is it really that hard to remove them, wash and re oil?

There were some concerns that the oil from the filter was contaminating the Air Flow sensors in some cars.
But K&N have done a lot of testing to try and find out if this was actually happening.
Their results showed that no oil from a "properly" loaded filter could be drawn off with the normal air flow through a system.
Maybe people are being careless and applying to much oil or not washing the filter before re loading it.

Either way if you maintain your filter as recommended by K&N it should be fine.

I have an S&B filter on my VW Golf for over 3 years and I've had no issues with it.

I even did this to my SC... I know it's ugly but I was experimenting to see if I could get a few more HP from my old girl.
It's not on the car now. It did change the character of the engine. It may have added a few ponies but I never dynoed the car before or after.
But it did make the revs drop very quickly which was unacceptable.

[red-beard]

How would a filter, on a modern FI engine, improve fuel economy?

[sc_rufctr]

Originally Posted by red-beard

How would a filter, on a modern FI engine, improve fuel economy?

Good question...

Best guess... The air being drawn in is less restricted.
So the air filling the cylinders may be at a slightly higher pressure than with the OEM filter.

More air = More oxygen producing more power. At the expense of leaning out the mixture slightly but
because the EFI system has some safety built into it this shouldn't be a problem.

Also... MSD state that their ignitions produce more power than OEM systems.
They even make this claim with their DIS4+ system that is designed for modern coil pack ignition.

I'm not sure any of it is true... It would take extensive Dyno testing to prove any of this.
Has anyone done independent testing?

[m21sniper]

Originally Posted by red-beard

How would a filter, on a modern FI engine, improve fuel economy?

If the old one was causing a restriction. Which it may or may not be doing depending on the airbox in question.

[Chocaholic]

Another K&N thread. Will keep this brief. A K&N filter is no better than a clean stock filter. Both provide all the air your engine could want under normal driving conditions. Any HP or fuel economy change is in your head. If you're replacing a plugged up stock filter with a new clean K&N...sure you'll see a difference. Otherwise, utter nonsense. Oh yes...the added porosity of the K&N is allowing particulate matter into your engine that it doesn't need. Stick with stock. It's worth the money.

Rant over....and briefly too!

[Porsche-O-Phile]

K&N is pure crap.

100% marketing, 0% quality.

There have been numerous studies posted about their products on a motorcycle forum I visit. Unless your vehicle's filter specifications for OEM happen to be TERRIBLE, K&N will be worse.

[red-beard]

Originally Posted by m21sniper

If the old one was causing a restriction. Which it may or may not be doing depending on the airbox in question.

Your throttle causes much more restriction. In the old days, with a carb'd engine, a restricted filter would make your engine run rich. Fuel flow depended on volumetric flow and differential pressure. A dirty filter creates a lower absolute pressure for the same throttle position and the carb meters too much fuel.

But with a MAP and/or mass flow sensor in your intake, the computer calculates exactly how much fuel you need.

The only thing you can gain with less restriction is maximum wide open throttle horsepower. With a modern fuel injected engine, you cannot get an efficiency gain.

There is another issue with K&N filters. The lower restriction allows more dirt into the engine. My engine rebuilder on my 914/6 thinks that is the reason my rings/clylinders were worn out.

[Superman]

A friend of mine runs a fairly large county maintenance operation. They service and maintain a bazillion pieces of heavy equipment, not to mention fleets of cars and trucks. He says that most paper filters have WAY more surface area than they need. In fact, they are designed to pass more than enough air volume, even when they are very dirty and plugged. Here comes the interesting part: Their filtering ability gets better the dirtier they are. To a point of course.

This friend relies on the findings and recommendations of manufacturers, suppliers, etc. They recommend waiting until the filter is VERY dirty. WAY dirtier than you guys would be comfortable with.

[sammyg2]

This has pretty much been summed up. A K&N will work better than an old clogged up filter but will not outperform a clean stock filter on most cars (probably all of them).
It will let more dirt in and wear out your engine faster but most of us don't keep a car long enough for that to be a factor.
Most modern intake systems are efficient to the point where the air filter is not the limiting factor anyway.
Plus if you let in more air, the modern FI system adds more fuel to keep the mixture right where it wants. More air = more available power, but not necessarily more fuel efficiency.

Same with cold air intake systems. the air is colder, so its more dense, which = more air. More air = more fuel. Increase in power, not economy.

UNLESS the engine was so bogged down before you had to put your foot in it more which changed the mapping to a richer section and the new filter doesn't require you to give it as much gas to go as fast (I really doubt that).

[Superman]

Originally Posted by sammyg2

A K&N will work better than an old clogged up filter but will not outperform a clean stock filter on most cars (probably all of them)..

This is my point. In at least some instances, and in fact probably most, maybe nearly all, the best possible filter is a dirty paper filter. The large amount of surface area allows sufficient flow, and the crud trapped in the filter effectively filters out finer contaminants than the new filter could catch.

[m21sniper]

Originally Posted by red-beard

Your throttle causes much more restriction. In the old days, with a carb'd engine, a restricted filter would make your engine run rich. Fuel flow depended on volumetric flow and differential pressure. A dirty filter creates a lower absolute pressure for the same throttle position and the carb meters too much fuel.

I didn't realize we were talking about carbureted cars?

I can give you a specific example where a K&N cone filter is a significant improvement over a stock factory airbox.

1985 and older Buick Grand National/T-type turbos. The factory airbox simply cannot flow the kind of air required when you make just a couple modifications to the vehicle.

What's more, a cone filter facilitates the use of aftermarket cold air induction systems, which do make a difference.

So, while they are to a large degree marketing creations, K&N's (or more specifically, large cones) have their place.

[myamoto1]

I agree with Porsche-O-Phile - K&N is more hype than a Fram oil filter.

I used a K&N filter for about 3 months on an older 4Runner ('85) that I used as a daily driver and for off-roading. I needed to pull apart the intake for some reason and found a thin layer of dust and grit inside the intake that was not there previously. I cleaned out the intake and switched back to a stock filter - no more dust or grit in the intake.

K&N's do flow better, but I would argue at a cost. The amount of crap those filter let through are more than I'd want in a $500 Toyota engine. I can't imagine why you'd want that on a $5000+ engine.

To further my point, my 911 came with a K&N installed - looked brand new. I tossed it. Those that know me, know how limited funds are for me. It litterally takes me months to save up for basic parts for my car. I often end up selling other belongings to fund Porsche parts. However, rather than re-selling a crap product and contributing to the destruction of someone else's engine and adding $20 to my pocket, I chose to put the K&N where it belongs - in the trash.

I'm amazed with all of the in depth analysis that has been done on these filters, that people still insist on putting them in their cars. If you have one, go hug your engine, it may be the last chance you have.

[Tim Hancock]

I have changed the stock paper airfilter along with the sparkplugs in my E36 BMW 325i once since I bought it with 140k on the clock. It now has 308,000 miles on it and still runs awesome using very little oil. Watercooled P-cars... pretty much the same situation. The only way I would bother with changing road going airfilters more often is if I drove them off road in dusty conditions often.

The tiny foam airfilter on my airplane gets changed once a year at annual inspection time even though I rarely fly it enough hours in a year to need it.

My MX race bikes got a freshly cleaned and oiled foam filter every race, as it would be covered in dirt..... My street driven cars.... not so much.

[sammyg2]

Originally Posted by Tim Hancock

My MX race bikes got a freshly cleaned and oiled foam filter every race, as it would be covered in dirt..... My street driven cars.... not so much.

Yep, I had oiled foam filters in my bike when I used to race desert in district 37. It got cleaned and re-oiled before every race, and the engine got overhauled after about 25 to 30 hours of use.

[red-beard]

Originally Posted by m21sniper

I didn't realize we were talking about carbureted cars?

I can give you a specific example where a K&N cone filter is a significant improvement over a stock factory airbox.

1985 and older Buick Grand National/T-type turbos. The factory airbox simply cannot flow the kind of air required when you make just a couple modifications to the vehicle.

What's more, a K&N facilitate the use of aftermarket cold air induction systems, which do make a difference.

So, while they are to a large degree marketing creations, K&N's (or more specifically, large cones) have their place.

He said his gas mileage improved by 8%. I call BS. Absolute maximum POWER yes, but not efficiency.

[m21sniper]

I was not speaking as to his gas mileage.

[gtc]

Originally Posted by Superman

A friend of mine runs a fairly large county maintenance operation. They service and maintain a bazillion pieces of heavy equipment, not to mention fleets of cars and trucks. He says that most paper filters have WAY more surface area than they need. In fact, they are designed to pass more than enough air volume, even when they are very dirty and plugged. Here comes the interesting part: Their filtering ability gets better the dirtier they are. To a point of course.

This friend relies on the findings and recommendations of manufacturers, suppliers, etc. They recommend waiting until the filter is VERY dirty. WAY dirtier than you guys would be comfortable with.

He should be running air cleaner service indicators. If he's running any Cat engines I'll be happy to send over a rep to restock his filter supply. Actually I think we sell parts for that green garbage too, now.

[Scott R]

On the 944 board when I was over there they had some great pictures of engines torn down that had been running K&N's (I have no idea about how they were maintained..the filters that is).

Anyway, the cylinder walls in the K&N equipped engine showed a lot of surface damage from particulate introduced into the cylinder. Those pictures alone insured I would never run them. Sadly, however, I do run them on my 911 but I'm doing everything I can to get paper filters for my weber rain shields. In fact a few of us are looking for someone to make them.

[Superman]

Originally Posted by gtc

He should be running air cleaner service indicators. If he's running any Cat engines I'll be happy to send over a rep to restock his filter supply. Actually I think we sell parts for that green garbage too, now.

It sound like you are in my friend's industry also. I don't even understand your post. All I know is that my friend's maintenance shop works closely with reps, including Cat. They analyze the heck out of used oil. They analyze the heck out of internal engine parts. And they apparently conclude that dirty air filters catch finer particles than clean filters do, while passing plenty of engine intake air volume. My friend reports that when filters are finally ready to actually be replaced, they are CAKED with dirt.