air filter upgrade

[later, Peter]

I just bought a 30th anniversary outback... extremely well maintained. I took a short trip (150 miles each way) & got pleasantly great mileage on the road (not so great in town with the ac blowin')...

the question is: will an upgrade to a K & N air filter provide noticably better mileage &/or effeciency for the engine?

by the way, I bought the "piston slap is a normal noise" b.s. because, as Paul Simon once said: "all lies & jest 'til a man hears what he wants to hear & disregards the rest".

Later,

Peter

[Setright]

I use K&N, and have done so in a number of cars.

 

Don't believe the "extra 5hp" stuff, the flow of a K&N is not that far superior to a paper element. However, that is a NEW paper element, and the flow rate will fall steadily, the K&N offers far less resistance as it gets dirty. So you get better consistency. Also, in the long run it's gonna be cheaper.

[99obw]

IMHO maximum engine longevity is achieved by using an OEM filter and changing it every 15k miles. K&N filters aren't all they are cracked up to be. The vast majority of OEMs use some sort of paper air filter. That tells me something.

 

In the endless search for fuel economy and performance, if there was a good engineering decision to be made regarding the use of oiled air filters, you can be certain the OEMs would be using them.

[Setright]

May I quote Laurel and Hardy??

 

"What an ignorance!"

 

 

If a company, especially a car company, can save even a nickel on a part, it will do so. Multiply it up by by the hundreds of thousands they produce, and that nickel will mean something - to them anyway.

 

It's all about percieved quality. Car companies prefer to spend money on a fancy set of headlights, and some sort of new texture on the interior plastic, so that it all looks more expensive.

 

An air filter hidden away under the bonnet won't impress in the showroom.

 

 

Try taking apart the exhaust system on your car and examine it's construction. The flanges are only welded on the outside, to keep them gas-tight, but inside the raw cut of the pipe is restricting the flow. Why? No-one will see if you spend extra time and money welding and sanding the insides to give a smooth flow. There is power and fuel being lost here, yet car companies are choosing to cut costs instead.

 

My 1990 Legacy intake had velocity stacks leading from each plenum into the next pipe. My 2000 Impreza has blunt edges. COST CUTTING!

[RallyKeith]

May I quote Laurel and Hardy??

 

"What an ignorance!"

 

Now now, you don't need to be that harsh.

 

Yes you've basically hit the nail on the head. Go to an autoparts store and compare the price of a Fram "paper" filter to that of a Fram Air Hog (Fram's rip off of K&N) Legacy paper filter is about $10 and the Oiled Air Hog as about $50. Using good old fashion 70% Gross Margin that means it cost about $3 to make the paper filter and about $15 to make the Oiled. Multply the difference by say even a modest 500,000 units a year and that adds up to $6,000,000 a year! So, right there are the numbers. It would cost a car company like GM Hundreds of Millions to use oiled filter technology.

 

Enough garbage, A K&N filter sohuld increase the gas mileage a little, but not much. Anything helps, and with out doing the math a K&N may or maynot be economical. Filter cleaning and oiling kits aren't free, so every two or three times you clean it you need to drop $10 on the kit.

 

Keith

[99obw]

You can't really compare the cost of the two types of filters, as the numbers of units manufactured per year is off by at least a couple of orders of magnitude. The economy of scale that applies to the paper element filters does not apply to the oiled filters. Paper, foam, and gauze are all very inexpensive raw materials.

 

I was not speaking of only cars. I have worked on string trimmers, diesel semis, bulldozers, and much of what comes in between. The only thing I have ever seen anything other than a paper air filter on is the cheapest of the consumer grade lawn and garden equipment. My cheap chain saw has a foam air filter, my nice one has a paper element. My cheap leaf blower has a foam air filter. My 63" trail mower has a paper filter. Any idea what kind of air filter they use on a $250,000.00 combine. Paper. I am not saying that paper filters are used on everything, just the vast majority.

 

My point with this is not to prove that I am right, but to illustrate the caution that one should exercize when trying to "outthink" the engineers that designed something. The decisions they make are often based on more complete and complex data than we have access to.

 

Regardless of application, when filtration quality and equipment longevity are priorities, paper is chosen by most engineers.

 

BTW: I run oiled foam pre-filters on all of my lawn equipment. Keeps the paper element cleaner and makes it last longer.

[hohieu]

Very interesting debate regarding economic principles. 99obw, I don't want to go off topic on this thread, but do you think the same economy of scale argument that you are making here would apply to the synthetic motor oil industry. I know from previous threads that you run Amsoil, in part, for its higher viscosity (Cst of about 12 at 100 degrees C), but do you think its higher price in comparison to, say, Mobil 1 equates to higher overall quality. I don't want to turn this air filter thread into an Amsoil/Mobil 1 debate -- just want you 2 cents on this specific question.

[RallyKeith]

You can't really compare the cost of the two types of filters, as the numbers of units manufactured per year is off by at least a couple of orders of magnitude. The economy of scale that applies to the paper element filters does not apply to the oiled filters. Paper, foam, and gauze are all very inexpensive raw materials.

 

I was not speaking of only cars. I have worked on string trimmers, diesel semis, bulldozers, and much of what comes in between. The only thing I have ever seen anything other than a paper air filter on is the cheapest of the consumer grade lawn and garden equipment. My cheap chain saw has a foam air filter, my nice one has a paper element. My cheap leaf blower has a foam air filter. My 63" trail mower has a paper filter. Any idea what kind of air filter they use on a $250,000.00 combine. Paper. I am not saying that paper filters are used on everything, just the vast majority.

 

Well, there is a big difference between what you find in a lawn mower and a K&N filter. Lawn movers come with something about the same pore size as a kitchen spounge.

 

 

 

My point with this is not to prove that I am right, but to illustrate the caution that one should exercize when trying to "outthink" the engineers that designed something. The decisions they make are often based on more complete and complex data than we have access to.

 

 

On that note, I'm not trying to out think anyone. I do though work on new product developement and design tools and testers. I feel its safe to say in that even though my title may me technician, I am really an engineer. Rule #1 for any engineer in a for profit company is cost. Every product we desing starts out with a product feature/spec list and a target cost. COST is a design element, and if I can make a product meet the spec with a $3 part or exceed the spec with a $15 part, you better believe I'm using the $3. Since there is no apparent gain to the end user using the oiled filter technology, the only reason to use it would be cost, and there is a serious cost disadvantage to them. That's really the bottom line.

[blitz]

I've tried both the Amsoil oiled-foam element and the aftermarket Purolator dry-paper element, and neither seemed to fit the airbox satisfactorily, so I've gone back to the OEM oiled-paper which honestly seems to be a high quality piece.

 

Up till now I've avoided the oiled-gauze types on account of being able to see a frightening amount of daylight through the element. Not scientific I realize, but it gives me peace of mind.

[99obw]

Well, there is a big difference between what you find in a lawn mower and a K&N filter. Lawn movers come with something about the same pore size as a kitchen spounge.

My point was cost. They use the cheapest filter possible. On better quality lawn equipment they don't use better foam, they use paper. On equipment where the cost of the filter is absolutely insignificant with regard to the overall cost($250,000 combine), they use paper.

 

On that note, I'm not trying to out think anyone. I do though work on new product developement and design tools and testers. I feel its safe to say in that even though my title may me technician, I am really an engineer. Rule #1 for any engineer in a for profit company is cost. Every product we desing starts out with a product feature/spec list and a target cost. COST is a design element, and if I can make a product meet the spec with a $3 part or exceed the spec with a $15 part, you better believe I'm using the $3. Since there is no apparent gain to the end user using the oiled filter technology, the only reason to use it would be cost, and there is a serious cost disadvantage to them. That's really the bottom line.

I disagree. Rule #1 is make the product work. Rule #2 is make it as cheaply as possible. Whether or not the features can be attained at the target cost should be determined at the functional specification stage. I work in an industry where this isn't as important as the automotive industry, but it is still a concern.

 

Very interesting debate regarding economic principles. 99obw, I don't want to go off topic on this thread, but do you think the same economy of scale argument that you are making here would apply to the synthetic motor oil industry. I know from previous threads that you run Amsoil, in part, for its higher viscosity (Cst of about 12 at 100 degrees C), but do you think its higher price in comparison to, say, Mobil 1 equates to higher overall quality. I don't want to turn this air filter thread into an Amsoil/Mobil 1 debate -- just want you 2 cents on this specific question.

I think Mobil 1 has a huge advantage here, and it's seen in the performance of their oil. As much as I like Amsoil I have to be objective. Since the last reformulation of Mobil 1 it appears that Amsoil is inferior. If Mobil 1 10w-30 wasn't so thin I would be using it. Now that the Outback is starting to use the Amsoil 10w-30 at a higher rate I am going to switch to a 5w-40, and Mobil 1 Truck and SUV 5w-40 is very tempting. I have a case of Amsoil 5w-40 on hand but it may be the last Amsoil I buy. I need to find a local source for a Mobil 1 5w-40 and some good filters.

[slo5oh]

You guys kill me.

 

See air through the filter? haaa!

when I was 16 we used to run my friends 350 camaro around town with no air filter, it made more horse power and there was a noticable tone difference to the exhaust.

K&N filters do make a difference. An air filter, any air filter "inhibits" air flow. The Idea is to "inhibit" air flow as little as possible. I agree with the "don't count on 5hp" statement though.

As for syn vs. petrol oil... I've seen the inside of a 400 hp engine pulled apart that ran normal crap oil... and I've seen the inside of my own motor (400hp also) that would go 10 or 15k on redline between changes. Mine was all nice and clean with a red coating over everything, the bearings looked new. The other was coated in black sludge, the bearings were scratched bad. True synthetic oil is a god send.

 

990bw,

Sorry if you already know this, but you can get Mobile 1 10-30, at wal-mart in a 5 qt. jug for about $20, along with some other temp ranges (not sure what ones). The best fitlers for the buck are the generic wal-mart ones, they are made by purilator and work great, for under $2. When you are there pick up a can of the engine restore. It comes in a silver tube, looks like a thin 1950s oil can. I have a friend that's been the head counter person at a local auto parts store turn me on to this stuff. Put it in with every oil change and it helps recondition your rings and stops blowby. My little 105k engine picked up quite a bit mid RPM tq. It surprised me.

[blitz]

You guys kill me.

 

See air through the filter? haaa!

when I was 16 we used to run my friends 350 camaro around town with no air filter, it made more horse power and there was a noticable tone difference to the exhaust.

K&N filters do make a difference. An air filter, any air filter "inhibits" air flow. The Idea is to "inhibit" air flow as little as possible. I agree with the "don't count on 5hp" statement though.

Your comparison between the K&N and an open intake puts forth my point in a way I was reluctant to do, thanks.

[cookie]

testing using a few different types of filters and a vacum guage. We satisfied ourselves that there was little to be gained from changing to oiled foam filters. I believe that someone did some tests on Bobistheoilguy. Try taking a look over there.

My cars use the best paper elements I can get. OEM Subaru on this car.

[Setright]

I cannot believe that anyone would doubt that cost plays a central role in car design.

[Ranger83]

Very few proponents of the K&N filters bother to document their actual mileage and performance before installing one, so there is little evidence about the benefits. My experience from racing is that any change you make always feels faster.

 

I worked for two years as an automotive supplier of large plastic parts to various manufacturers - the Big Three and VW. Of course engineers are concerned about cost, but they are also designing parts that may be tooled to produce millions of parts. Very few engineers spend their time making things worse.

 

With the CAFE standards in the U.S., where increasing your fleet mileage allows you to sell large, highly profitable SUV's, if an exhaust flange or air filter or vortex creator saved a few tenths of a mpg, they'd be OEM'd. It appears that some manufacturers subsidize the sale of the highest MPG cars, because they can sell three SUV-Marus for each one sold.

[hohieu]

The economy of scale that applies to the paper element filters does not apply to the oiled filters. Paper, foam, and gauze are all very inexpensive raw materials.

I think we should remember this very good point when thinking about cost. I have ridden motorcycles all my life, for which OEM parts, including air filters (whether they be foam or paper) cost upwards of 2 to 3 times as much as their automotive counterparts. It is the "economy of scale" that accounts for lower prices on on a car air filter that is almost identitical to that of a motorcycle. Hence, given the law of demand, and the inverse relationship between demand and price, if every automotive company determined that an air hog or K&N filter improved both mileage and power, the prices for these items would decrease significantly.

 

Some of the higher prices for aftermarket "performance enhancing" items can also be attributed to marketing, which tends to sell men "power and performance," while other industries push products to women that claim to keep them young forever -- both often at exorbitantly high prices.

 

 

Very few engineers spend their time making things worse.

 

With the CAFE standards in the U.S., where increasing your fleet mileage allows you to sell large, highly profitable SUV's, if an exhaust flange or air filter or vortex creator saved a few tenths of a mpg, they'd be OEM'd. It appears that some manufacturers subsidize the sale of the highest MPG cars, because they can sell three SUV-Marus for each one sold.

Agreed, this is a good thing to keep in mind when faced with any product that claims to improve mileage and performance. I saw a recent ad for this thing called a "FuelMaster" which consisted of two magnets that clamped together around your intake fuel hose. It claimed to atomize the hydrocarbon clusters in gasoline, thereby resulting in more efficient buring of the fuel and increasing fuel mileage by 10-20%. Again, if a $30 magnet increased mileage by this percentage, every automotive manufacturer would be using them. Remembering back to a high school chemistry class, I also realized hydrocarbons in gasoline have dipole moments too insignificant to cause "clustering."

 

And to continue with the motorcycle example, aftermarket performance products (exhaust, fuel delivery, and air intake) in this parallel industry do increase power when properly calibrated to achieve the stoichiometric ratio, but motorcycles do not have to pass EPA emissions inspections on an annual basis, only in production. With carbureted models, this would often involve rejetting, and now, some even install aftermarket computers on fuel injected models in order to alter fuel delivery and ignition timing for the goal of increasing horsepower, but you can only measure real gains by doing before and after dynometer runs.

[cookie]

anything but noise at wide open throttle. I don't know about you guys but my street cars spend very little time at WOT since I became an adult.

I agree that the only way you will see much change is on a before and after dyno run. I also agree that when changing something you usually feel faster if it makes more noise.

Speed equipment and scams have been around since Henry gave us the Model T.

Some of it works and some of it doesn't and most of it makes somebody feel good.

The basics are allways the same, the engine is an air pump and the more you get in and out the more power you make.

The question is where is it worthwhile for your dollar.If someone makes thier own intake and gains 1-2 real world HP for 10 bucks it is worth it, especially if they had fun doing it. If it cost $300 for an aftermarket intake for the same HP gain it is not worthwhile to me.

The real thing to watch out for is stuff like spark intensifiers and little do dads that whirl in the intake and claim more HP and gas mileage. I know some of you guys belive you can rebuild your engine with a can of goop that only thickens the oil, but honest folks, a set of rings will help a lot more.

[Ranger83]

See air through the filter? haaa!

when I was 16 we used to run my friends 350 camaro around town with no air filter, it made more horse power and there was a noticable tone difference to the exhaust.

How much more horsepower? I road-raced a VW Scirocco years ago and tried this. The intake tract is a lot louder.Maybe I had more horsepower, but there was no difference in my lap times.

 

I suppose you are "running" K&N's now, then? Have you also researched the best type of oil to drench it in? I think it's hilarious because some of the antique cars we had used the same type of oil dip filter.

[myles]

May I quote Laurel and Hardy??

 

"What an ignorance!"

 

 

If a company, especially a car company, can save even a nickel on a part, it will do so. Multiply it up by by the hundreds of thousands they produce, and that nickel will mean something - to them anyway.

 

It's all about percieved quality. Car companies prefer to spend money on a fancy set of headlights, and some sort of new texture on the interior plastic, so that it all looks more expensive.

 

An air filter hidden away under the bonnet won't impress in the showroom.

 

 

Try taking apart the exhaust system on your car and examine it's construction. The flanges are only welded on the outside, to keep them gas-tight, but inside the raw cut of the pipe is restricting the flow. Why? No-one will see if you spend extra time and money welding and sanding the insides to give a smooth flow. There is power and fuel being lost here, yet car companies are choosing to cut costs instead.

 

My 1990 Legacy intake had velocity stacks leading from each plenum into the next pipe. My 2000 Impreza has blunt edges. COST CUTTING!

 

In the US, it's not about saving US$.05 on a part. It's about increasing the fuel economy by .01 mi/gal (thanks to CAFE). That's why some cars are shipping with (and the owner's manual is recommending the use of) 5W20!

[Setright]

Yes, yes, I know about Corporate Average Fuel Economy.

 

Even so, I have to sound like a broken record, because no matter what your CAFE rating, you still have to be able to sell your cars.

[urabus1995]

I am fascinated by the direction that this thread has taken. At long last people are making real sense of this issue. I was going to make mods to my intake etc, after hearing claims on this very forum. I doubted that the ECU would like the proposed changes, and did not do any of them.

 

I am very lucky to live in a very clean air country, with fairly low air temps most of the time. I presume then , that I will be pulling more air /stroke than someone living in Arizona or California, plus I will not have the continuous clogging of filters due to dust and sand etc. ???.

I may be wrong, but I presume that the ECU alters the amount of fuel to match the mass of air or O2 that the sensors detect. If you get more air going in, you will burn more fuel? That must make a slight change to HP, but surely it can only decrease economy?

[blitz]

Yeah, increased elevation and increased temperatures both result in "thinner" air and therefore reduced power. The ECU compensates in both instances by reducing fuel accordingly. One difference however is that increased elevation causes the ECU to advance timing, wheres increased temperature causes the ECU to retard timing.

 

Driving style/highway speed and tire inflation will affect your fuel ecomony more than air tenperature will, except in very cold weather where the lubes get thick.

[Ranger83]

Engine control systems sense air mass, not density. That's how they control the mixture so well.

[slo5oh]

How much more horsepower? I road-raced a VW Scirocco years ago and tried this. The intake tract is a lot louder. Maybe I had more horsepower, but there was no difference in my lap times.

 

 

I suppose you are "running" K&N's now, then? Have you also researched the best type of oil to drench it in? I think it's hilarious because some of the antique cars we had used the same type of oil dip filter.

 

 

Like I said, we were 16… or should I say, I was 16, he was still 15 and driving without a license. Luckily for him his father was a cop so he always got a slap on the hand instead of a ticket. I do still run a K&N in both my mustangs. His problem could have been from an old dirty air filter, the sound could be because without the air filter nothing muffles the holly double pumper, who knows.

 

I have a 10" cone style K&N filter stuck on the end of my MAF. When you put a supercharger on a 5.0 you have no choice but to ditch the stock panel filter. That's why I bought my first K&N. Not to mention the supercharged engine was sucking over twice the air of a stock 5.0… so I obviously needed a filter that could flow more air.

 

 

I honestly had no intention of buying one for my Subaru, but even at Wal-mart it cost me over $20 for new paper filter last year. For $10 more I can get a K&N or other reusable filter, so when this one gets dirty it will be replaced with one of those.

[slo5oh]

 

The basics are always the same, the engine is an air pump and the more you get in and out the more power you make.

 

The question is where is it worthwhile for your dollar. If someone makes their own intake and gains 1-2 real world HP for 10 bucks it is worth it, especially if they had fun doing it. If it cost $300 for an aftermarket intake for the same HP gain it is not worthwhile to me.

 

The real thing to watch out for is stuff like spark intensifiers and little do dads that whirl in the intake and claim more HP and gas mileage. I know some of you guys believe you can rebuild your engine with a can of goop that only thickens the oil, but honest folks, a set of rings will help a lot more.

 

 

You make a lot of great points.

 

more air in + more air out = more HP

 

HP/$ spent = value

 

Spark intensifiers have their purpose. In turbo, supercharged, and Nitros situations you can "blow out" the spark when making too much cylinder pressure.

 

Intake swirley do dads.. The science makes sense... but I don't see it.

 

Now if you are talking about a good port job on the intake... well well... there's lots of power to be had. Even SVT (fords special vehicles team) to make the power they wanted had the contour SVT's intake manifold extrude honed. For those that don't know, this is a process that runs a gooey gel through the intake that acts like liquid sandpaper and all but polishes the surfaces smooth. Smooth intake runners make little to no air turbulence allowing for air to pass through faster thus allowing more air into the engine.

 

 

And the last one the cans of goop that thicken your oil. I used to use the cheapest one I could find when I 17 driving a 78 Honda with 180k? 280? dunno since the odometer only read to the 10s of thousands. It did little for me, but I added less oil weekly. I have a good friend that many people consider the best parts man in northern cali tell me that the silver bottle of "engine restore" will just about stop your oil consumption and restore some power. Having ripped apart and rebuilt, with my own 2 hands, several 302s I totally agree that nothing can compare to new rings and bearings, but lots of people just can't afford that. Even more wouldn't know how to do it themselves, and probably shouldn't, so it will cost lots of $. When he told me about the engine restore, he was putting new rings and bearings into a geo metro for the second time on this over 300k engine. This little geo started smoking bad over 50k earlier and the owner was using the engine restore to keep the smoke at bay until he could afford to have my friend rebuild it.